| Commit message (Collapse) | Author |
|---|
|
commit 9137bb27e60e554dab694eafa4cca241fa3a694f upstream.
Add the PR_SPEC_INDIRECT_BRANCH option for the PR_GET_SPECULATION_CTRL and
PR_SET_SPECULATION_CTRL prctls to allow fine grained per task control of
indirect branch speculation via STIBP and IBPB.
Invocations:
Check indirect branch speculation status with
- prctl(PR_GET_SPECULATION_CTRL, PR_SPEC_INDIRECT_BRANCH, 0, 0, 0);
Enable indirect branch speculation with
- prctl(PR_SET_SPECULATION_CTRL, PR_SPEC_INDIRECT_BRANCH, PR_SPEC_ENABLE, 0, 0);
Disable indirect branch speculation with
- prctl(PR_SET_SPECULATION_CTRL, PR_SPEC_INDIRECT_BRANCH, PR_SPEC_DISABLE, 0, 0);
Force disable indirect branch speculation with
- prctl(PR_SET_SPECULATION_CTRL, PR_SPEC_INDIRECT_BRANCH, PR_SPEC_FORCE_DISABLE, 0, 0);
See Documentation/userspace-api/spec_ctrl.rst.
Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Ingo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Jiri Kosina <jkosina@suse.cz>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: David Woodhouse <dwmw@amazon.co.uk>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Casey Schaufler <casey.schaufler@intel.com>
Cc: Asit Mallick <asit.k.mallick@intel.com>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Jon Masters <jcm@redhat.com>
Cc: Waiman Long <longman9394@gmail.com>
Cc: Greg KH <gregkh@linuxfoundation.org>
Cc: Dave Stewart <david.c.stewart@intel.com>
Cc: Kees Cook <keescook@chromium.org>
Link: https://lkml.kernel.org/r/20181125185005.866780996@linutronix.de
[bwh: Backported to 4.4:
- Renumber the PFA flags
- Drop changes in tools/include/uapi/linux/prctl.h
- Adjust filename]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
|
|
commit 356e4bfff2c5489e016fdb925adbf12a1e3950ee upstream
For certain use cases it is desired to enforce mitigations so they cannot
be undone afterwards. That's important for loader stubs which want to
prevent a child from disabling the mitigation again. Will also be used for
seccomp(). The extra state preserving of the prctl state for SSB is a
preparatory step for EBPF dymanic speculation control.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Srivatsa S. Bhat <srivatsa@csail.mit.edu>
Reviewed-by: Matt Helsley (VMware) <matt.helsley@gmail.com>
Reviewed-by: Alexey Makhalov <amakhalov@vmware.com>
Reviewed-by: Bo Gan <ganb@vmware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
|
|
commit b617cfc858161140d69cc0b5cc211996b557a1c7 upstream
Add two new prctls to control aspects of speculation related vulnerabilites
and their mitigations to provide finer grained control over performance
impacting mitigations.
PR_GET_SPECULATION_CTRL returns the state of the speculation misfeature
which is selected with arg2 of prctl(2). The return value uses bit 0-2 with
the following meaning:
Bit Define Description
0 PR_SPEC_PRCTL Mitigation can be controlled per task by
PR_SET_SPECULATION_CTRL
1 PR_SPEC_ENABLE The speculation feature is enabled, mitigation is
disabled
2 PR_SPEC_DISABLE The speculation feature is disabled, mitigation is
enabled
If all bits are 0 the CPU is not affected by the speculation misfeature.
If PR_SPEC_PRCTL is set, then the per task control of the mitigation is
available. If not set, prctl(PR_SET_SPECULATION_CTRL) for the speculation
misfeature will fail.
PR_SET_SPECULATION_CTRL allows to control the speculation misfeature, which
is selected by arg2 of prctl(2) per task. arg3 is used to hand in the
control value, i.e. either PR_SPEC_ENABLE or PR_SPEC_DISABLE.
The common return values are:
EINVAL prctl is not implemented by the architecture or the unused prctl()
arguments are not 0
ENODEV arg2 is selecting a not supported speculation misfeature
PR_SET_SPECULATION_CTRL has these additional return values:
ERANGE arg3 is incorrect, i.e. it's not either PR_SPEC_ENABLE or PR_SPEC_DISABLE
ENXIO prctl control of the selected speculation misfeature is disabled
The first supported controlable speculation misfeature is
PR_SPEC_STORE_BYPASS. Add the define so this can be shared between
architectures.
Based on an initial patch from Tim Chen and mostly rewritten.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Srivatsa S. Bhat <srivatsa@csail.mit.edu>
Reviewed-by: Matt Helsley (VMware) <matt.helsley@gmail.com>
Reviewed-by: Alexey Makhalov <amakhalov@vmware.com>
Reviewed-by: Bo Gan <ganb@vmware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
|
|
Userspace processes often have multiple allocators that each do
anonymous mmaps to get memory. When examining memory usage of
individual processes or systems as a whole, it is useful to be
able to break down the various heaps that were allocated by
each layer and examine their size, RSS, and physical memory
usage.
This patch adds a user pointer to the shared union in
vm_area_struct that points to a null terminated string inside
the user process containing a name for the vma. vmas that
point to the same address will be merged, but vmas that
point to equivalent strings at different addresses will
not be merged.
Userspace can set the name for a region of memory by calling
prctl(PR_SET_VMA, PR_SET_VMA_ANON_NAME, start, len, (unsigned long)name);
Setting the name to NULL clears it.
The names of named anonymous vmas are shown in /proc/pid/maps
as [anon:<name>] and in /proc/pid/smaps in a new "Name" field
that is only present for named vmas. If the userspace pointer
is no longer valid all or part of the name will be replaced
with "<fault>".
The idea to store a userspace pointer to reduce the complexity
within mm (at the expense of the complexity of reading
/proc/pid/mem) came from Dave Hansen. This results in no
runtime overhead in the mm subsystem other than comparing
the anon_name pointers when considering vma merging. The pointer
is stored in a union with fieds that are only used on file-backed
mappings, so it does not increase memory usage.
Includes fix from Jed Davis <jld@mozilla.com> for typo in
prctl_set_vma_anon_name, which could attempt to set the name
across two vmas at the same time due to a typo, which might
corrupt the vma list. Fix it to use tmp instead of end to limit
the name setting to a single vma at a time.
Change-Id: I9aa7b6b5ef536cd780599ba4e2fba8ceebe8b59f
Signed-off-by: Dmitry Shmidt <dimitrysh@google.com>
|
|
PR_SET_TIMERSLACK_PID value keep colliding with that of
newer prctls in mainline (e.g. first with PR_SET_THP_DISABLE,
and again with PR_MPX_ENABLE_MANAGEMENT).
So reset PR_SET_TIMERSLACK_PID to a large number so as to
avoid conflict in the near term while it is out of mainline
tree.
Corresponding Change-Id up for review in platform/system/core
is Icd8c658c8eb62136dc26c2c4c94f7782e9827cdb
Change-Id: I061b25473acc020c13ee22ecfb32336bc358e76a
Signed-off-by: Amit Pundir <amit.pundir@linaro.org>
|
|
thread.
Second argument is similar to PR_SET_TIMERSLACK, if non-zero then the
slack is set to that value otherwise sets it to the default for the thread.
Takes PID of the thread as the third argument.
This allows power/performance management software to set timer slack for
other threads according to its policy for the thread (such as when the
thread is designated foreground vs. background activity)
Change-Id: I744d451ff4e60dae69f38f53948ff36c51c14a3f
Signed-off-by: Ruchi Kandoi <kandoiruchi@google.com>
|
|
Credit where credit is due: this idea comes from Christoph Lameter with
a lot of valuable input from Serge Hallyn. This patch is heavily based
on Christoph's patch.
===== The status quo =====
On Linux, there are a number of capabilities defined by the kernel. To
perform various privileged tasks, processes can wield capabilities that
they hold.
Each task has four capability masks: effective (pE), permitted (pP),
inheritable (pI), and a bounding set (X). When the kernel checks for a
capability, it checks pE. The other capability masks serve to modify
what capabilities can be in pE.
Any task can remove capabilities from pE, pP, or pI at any time. If a
task has a capability in pP, it can add that capability to pE and/or pI.
If a task has CAP_SETPCAP, then it can add any capability to pI, and it
can remove capabilities from X.
Tasks are not the only things that can have capabilities; files can also
have capabilities. A file can have no capabilty information at all [1].
If a file has capability information, then it has a permitted mask (fP)
and an inheritable mask (fI) as well as a single effective bit (fE) [2].
File capabilities modify the capabilities of tasks that execve(2) them.
A task that successfully calls execve has its capabilities modified for
the file ultimately being excecuted (i.e. the binary itself if that
binary is ELF or for the interpreter if the binary is a script.) [3] In
the capability evolution rules, for each mask Z, pZ represents the old
value and pZ' represents the new value. The rules are:
pP' = (X & fP) | (pI & fI)
pI' = pI
pE' = (fE ? pP' : 0)
X is unchanged
For setuid binaries, fP, fI, and fE are modified by a moderately
complicated set of rules that emulate POSIX behavior. Similarly, if
euid == 0 or ruid == 0, then fP, fI, and fE are modified differently
(primary, fP and fI usually end up being the full set). For nonroot
users executing binaries with neither setuid nor file caps, fI and fP
are empty and fE is false.
As an extra complication, if you execute a process as nonroot and fE is
set, then the "secure exec" rules are in effect: AT_SECURE gets set,
LD_PRELOAD doesn't work, etc.
This is rather messy. We've learned that making any changes is
dangerous, though: if a new kernel version allows an unprivileged
program to change its security state in a way that persists cross
execution of a setuid program or a program with file caps, this
persistent state is surprisingly likely to allow setuid or file-capped
programs to be exploited for privilege escalation.
===== The problem =====
Capability inheritance is basically useless.
If you aren't root and you execute an ordinary binary, fI is zero, so
your capabilities have no effect whatsoever on pP'. This means that you
can't usefully execute a helper process or a shell command with elevated
capabilities if you aren't root.
On current kernels, you can sort of work around this by setting fI to
the full set for most or all non-setuid executable files. This causes
pP' = pI for nonroot, and inheritance works. No one does this because
it's a PITA and it isn't even supported on most filesystems.
If you try this, you'll discover that every nonroot program ends up with
secure exec rules, breaking many things.
This is a problem that has bitten many people who have tried to use
capabilities for anything useful.
===== The proposed change =====
This patch adds a fifth capability mask called the ambient mask (pA).
pA does what most people expect pI to do.
pA obeys the invariant that no bit can ever be set in pA if it is not
set in both pP and pI. Dropping a bit from pP or pI drops that bit from
pA. This ensures that existing programs that try to drop capabilities
still do so, with a complication. Because capability inheritance is so
broken, setting KEEPCAPS, using setresuid to switch to nonroot uids, and
then calling execve effectively drops capabilities. Therefore,
setresuid from root to nonroot conditionally clears pA unless
SECBIT_NO_SETUID_FIXUP is set. Processes that don't like this can
re-add bits to pA afterwards.
The capability evolution rules are changed:
pA' = (file caps or setuid or setgid ? 0 : pA)
pP' = (X & fP) | (pI & fI) | pA'
pI' = pI
pE' = (fE ? pP' : pA')
X is unchanged
If you are nonroot but you have a capability, you can add it to pA. If
you do so, your children get that capability in pA, pP, and pE. For
example, you can set pA = CAP_NET_BIND_SERVICE, and your children can
automatically bind low-numbered ports. Hallelujah!
Unprivileged users can create user namespaces, map themselves to a
nonzero uid, and create both privileged (relative to their namespace)
and unprivileged process trees. This is currently more or less
impossible. Hallelujah!
You cannot use pA to try to subvert a setuid, setgid, or file-capped
program: if you execute any such program, pA gets cleared and the
resulting evolution rules are unchanged by this patch.
Users with nonzero pA are unlikely to unintentionally leak that
capability. If they run programs that try to drop privileges, dropping
privileges will still work.
It's worth noting that the degree of paranoia in this patch could
possibly be reduced without causing serious problems. Specifically, if
we allowed pA to persist across executing non-pA-aware setuid binaries
and across setresuid, then, naively, the only capabilities that could
leak as a result would be the capabilities in pA, and any attacker
*already* has those capabilities. This would make me nervous, though --
setuid binaries that tried to privilege-separate might fail to do so,
and putting CAP_DAC_READ_SEARCH or CAP_DAC_OVERRIDE into pA could have
unexpected side effects. (Whether these unexpected side effects would
be exploitable is an open question.) I've therefore taken the more
paranoid route. We can revisit this later.
An alternative would be to require PR_SET_NO_NEW_PRIVS before setting
ambient capabilities. I think that this would be annoying and would
make granting otherwise unprivileged users minor ambient capabilities
(CAP_NET_BIND_SERVICE or CAP_NET_RAW for example) much less useful than
it is with this patch.
===== Footnotes =====
[1] Files that are missing the "security.capability" xattr or that have
unrecognized values for that xattr end up with has_cap set to false.
The code that does that appears to be complicated for no good reason.
[2] The libcap capability mask parsers and formatters are dangerously
misleading and the documentation is flat-out wrong. fE is *not* a mask;
it's a single bit. This has probably confused every single person who
has tried to use file capabilities.
[3] Linux very confusingly processes both the script and the interpreter
if applicable, for reasons that elude me. The results from thinking
about a script's file capabilities and/or setuid bits are mostly
discarded.
Preliminary userspace code is here, but it needs updating:
https://git.kernel.org/cgit/linux/kernel/git/luto/util-linux-playground.git/commit/?h=cap_ambient&id=7f5afbd175d2
Here is a test program that can be used to verify the functionality
(from Christoph):
/*
* Test program for the ambient capabilities. This program spawns a shell
* that allows running processes with a defined set of capabilities.
*
* (C) 2015 Christoph Lameter <cl@linux.com>
* Released under: GPL v3 or later.
*
*
* Compile using:
*
* gcc -o ambient_test ambient_test.o -lcap-ng
*
* This program must have the following capabilities to run properly:
* Permissions for CAP_NET_RAW, CAP_NET_ADMIN, CAP_SYS_NICE
*
* A command to equip the binary with the right caps is:
*
* setcap cap_net_raw,cap_net_admin,cap_sys_nice+p ambient_test
*
*
* To get a shell with additional caps that can be inherited by other processes:
*
* ./ambient_test /bin/bash
*
*
* Verifying that it works:
*
* From the bash spawed by ambient_test run
*
* cat /proc/$$/status
*
* and have a look at the capabilities.
*/
#include <stdlib.h>
#include <stdio.h>
#include <errno.h>
#include <cap-ng.h>
#include <sys/prctl.h>
#include <linux/capability.h>
/*
* Definitions from the kernel header files. These are going to be removed
* when the /usr/include files have these defined.
*/
#define PR_CAP_AMBIENT 47
#define PR_CAP_AMBIENT_IS_SET 1
#define PR_CAP_AMBIENT_RAISE 2
#define PR_CAP_AMBIENT_LOWER 3
#define PR_CAP_AMBIENT_CLEAR_ALL 4
static void set_ambient_cap(int cap)
{
int rc;
capng_get_caps_process();
rc = capng_update(CAPNG_ADD, CAPNG_INHERITABLE, cap);
if (rc) {
printf("Cannot add inheritable cap\n");
exit(2);
}
capng_apply(CAPNG_SELECT_CAPS);
/* Note the two 0s at the end. Kernel checks for these */
if (prctl(PR_CAP_AMBIENT, PR_CAP_AMBIENT_RAISE, cap, 0, 0)) {
perror("Cannot set cap");
exit(1);
}
}
int main(int argc, char **argv)
{
int rc;
set_ambient_cap(CAP_NET_RAW);
set_ambient_cap(CAP_NET_ADMIN);
set_ambient_cap(CAP_SYS_NICE);
printf("Ambient_test forking shell\n");
if (execv(argv[1], argv + 1))
perror("Cannot exec");
return 0;
}
Signed-off-by: Christoph Lameter <cl@linux.com> # Original author
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Acked-by: Serge E. Hallyn <serge.hallyn@ubuntu.com>
Acked-by: Kees Cook <keescook@chromium.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Aaron Jones <aaronmdjones@gmail.com>
Cc: Ted Ts'o <tytso@mit.edu>
Cc: Andrew G. Morgan <morgan@kernel.org>
Cc: Mimi Zohar <zohar@linux.vnet.ibm.com>
Cc: Austin S Hemmelgarn <ahferroin7@gmail.com>
Cc: Markku Savela <msa@moth.iki.fi>
Cc: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Cc: James Morris <james.l.morris@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
Userland code may be built using an ABI which permits linking to objects
that have more restrictive floating point requirements. For example,
userland code may be built to target the O32 FPXX ABI. Such code may be
linked with other FPXX code, or code built for either one of the more
restrictive FP32 or FP64. When linking with more restrictive code, the
overall requirement of the process becomes that of the more restrictive
code. The kernel has no way to know in advance which mode the process
will need to be executed in, and indeed it may need to change during
execution. The dynamic loader is the only code which will know the
overall required mode, and so it needs to have a means to instruct the
kernel to switch the FP mode of the process.
This patch introduces 2 new options to the prctl syscall which provide
such a capability. The FP mode of the process is represented as a
simple bitmask combining a number of mode bits mirroring those present
in the hardware. Userland can either retrieve the current FP mode of
the process:
mode = prctl(PR_GET_FP_MODE);
or modify the current FP mode of the process:
err = prctl(PR_SET_FP_MODE, new_mode);
Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Cc: Matthew Fortune <matthew.fortune@imgtec.com>
Cc: Markos Chandras <markos.chandras@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/8899/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
|
|
This is really the meat of the MPX patch set. If there is one patch to
review in the entire series, this is the one. There is a new ABI here
and this kernel code also interacts with userspace memory in a
relatively unusual manner. (small FAQ below).
Long Description:
This patch adds two prctl() commands to provide enable or disable the
management of bounds tables in kernel, including on-demand kernel
allocation (See the patch "on-demand kernel allocation of bounds tables")
and cleanup (See the patch "cleanup unused bound tables"). Applications
do not strictly need the kernel to manage bounds tables and we expect
some applications to use MPX without taking advantage of this kernel
support. This means the kernel can not simply infer whether an application
needs bounds table management from the MPX registers. The prctl() is an
explicit signal from userspace.
PR_MPX_ENABLE_MANAGEMENT is meant to be a signal from userspace to
require kernel's help in managing bounds tables.
PR_MPX_DISABLE_MANAGEMENT is the opposite, meaning that userspace don't
want kernel's help any more. With PR_MPX_DISABLE_MANAGEMENT, the kernel
won't allocate and free bounds tables even if the CPU supports MPX.
PR_MPX_ENABLE_MANAGEMENT will fetch the base address of the bounds
directory out of a userspace register (bndcfgu) and then cache it into
a new field (->bd_addr) in the 'mm_struct'. PR_MPX_DISABLE_MANAGEMENT
will set "bd_addr" to an invalid address. Using this scheme, we can
use "bd_addr" to determine whether the management of bounds tables in
kernel is enabled.
Also, the only way to access that bndcfgu register is via an xsaves,
which can be expensive. Caching "bd_addr" like this also helps reduce
the cost of those xsaves when doing table cleanup at munmap() time.
Unfortunately, we can not apply this optimization to #BR fault time
because we need an xsave to get the value of BNDSTATUS.
==== Why does the hardware even have these Bounds Tables? ====
MPX only has 4 hardware registers for storing bounds information.
If MPX-enabled code needs more than these 4 registers, it needs to
spill them somewhere. It has two special instructions for this
which allow the bounds to be moved between the bounds registers
and some new "bounds tables".
They are similar conceptually to a page fault and will be raised by
the MPX hardware during both bounds violations or when the tables
are not present. This patch handles those #BR exceptions for
not-present tables by carving the space out of the normal processes
address space (essentially calling the new mmap() interface indroduced
earlier in this patch set.) and then pointing the bounds-directory
over to it.
The tables *need* to be accessed and controlled by userspace because
the instructions for moving bounds in and out of them are extremely
frequent. They potentially happen every time a register pointing to
memory is dereferenced. Any direct kernel involvement (like a syscall)
to access the tables would obviously destroy performance.
==== Why not do this in userspace? ====
This patch is obviously doing this allocation in the kernel.
However, MPX does not strictly *require* anything in the kernel.
It can theoretically be done completely from userspace. Here are
a few ways this *could* be done. I don't think any of them are
practical in the real-world, but here they are.
Q: Can virtual space simply be reserved for the bounds tables so
that we never have to allocate them?
A: As noted earlier, these tables are *HUGE*. An X-GB virtual
area needs 4*X GB of virtual space, plus 2GB for the bounds
directory. If we were to preallocate them for the 128TB of
user virtual address space, we would need to reserve 512TB+2GB,
which is larger than the entire virtual address space today.
This means they can not be reserved ahead of time. Also, a
single process's pre-popualated bounds directory consumes 2GB
of virtual *AND* physical memory. IOW, it's completely
infeasible to prepopulate bounds directories.
Q: Can we preallocate bounds table space at the same time memory
is allocated which might contain pointers that might eventually
need bounds tables?
A: This would work if we could hook the site of each and every
memory allocation syscall. This can be done for small,
constrained applications. But, it isn't practical at a larger
scale since a given app has no way of controlling how all the
parts of the app might allocate memory (think libraries). The
kernel is really the only place to intercept these calls.
Q: Could a bounds fault be handed to userspace and the tables
allocated there in a signal handler instead of in the kernel?
A: (thanks to tglx) mmap() is not on the list of safe async
handler functions and even if mmap() would work it still
requires locking or nasty tricks to keep track of the
allocation state there.
Having ruled out all of the userspace-only approaches for managing
bounds tables that we could think of, we create them on demand in
the kernel.
Based-on-patch-by: Qiaowei Ren <qiaowei.ren@intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Cc: linux-mm@kvack.org
Cc: linux-mips@linux-mips.org
Cc: Dave Hansen <dave@sr71.net>
Link: http://lkml.kernel.org/r/20141114151829.AD4310DE@viggo.jf.intel.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
|
|
During development of c/r we've noticed that in case if we need to support
user namespaces we face a problem with capabilities in prctl(PR_SET_MM,
...) call, in particular once new user namespace is created
capable(CAP_SYS_RESOURCE) no longer passes.
A approach is to eliminate CAP_SYS_RESOURCE check but pass all new values
in one bundle, which would allow the kernel to make more intensive test
for sanity of values and same time allow us to support checkpoint/restore
of user namespaces.
Thus a new command PR_SET_MM_MAP introduced. It takes a pointer of
prctl_mm_map structure which carries all the members to be updated.
prctl(PR_SET_MM, PR_SET_MM_MAP, struct prctl_mm_map *, size)
struct prctl_mm_map {
__u64 start_code;
__u64 end_code;
__u64 start_data;
__u64 end_data;
__u64 start_brk;
__u64 brk;
__u64 start_stack;
__u64 arg_start;
__u64 arg_end;
__u64 env_start;
__u64 env_end;
__u64 *auxv;
__u32 auxv_size;
__u32 exe_fd;
};
All members except @exe_fd correspond ones of struct mm_struct. To figure
out which available values these members may take here are meanings of the
members.
- start_code, end_code: represent bounds of executable code area
- start_data, end_data: represent bounds of data area
- start_brk, brk: used to calculate bounds for brk() syscall
- start_stack: used when accounting space needed for command
line arguments, environment and shmat() syscall
- arg_start, arg_end, env_start, env_end: represent memory area
supplied for command line arguments and environment variables
- auxv, auxv_size: carries auxiliary vector, Elf format specifics
- exe_fd: file descriptor number for executable link (/proc/self/exe)
Thus we apply the following requirements to the values
1) Any member except @auxv, @auxv_size, @exe_fd is rather an address
in user space thus it must be laying inside [mmap_min_addr, mmap_max_addr)
interval.
2) While @[start|end]_code and @[start|end]_data may point to an nonexisting
VMAs (say a program maps own new .text and .data segments during execution)
the rest of members should belong to VMA which must exist.
3) Addresses must be ordered, ie @start_ member must not be greater or
equal to appropriate @end_ member.
4) As in regular Elf loading procedure we require that @start_brk and
@brk be greater than @end_data.
5) If RLIMIT_DATA rlimit is set to non-infinity new values should not
exceed existing limit. Same applies to RLIMIT_STACK.
6) Auxiliary vector size must not exceed existing one (which is
predefined as AT_VECTOR_SIZE and depends on architecture).
7) File descriptor passed in @exe_file should be pointing
to executable file (because we use existing prctl_set_mm_exe_file_locked
helper it ensures that the file we are going to use as exe link has all
required permission granted).
Now about where these members are involved inside kernel code:
- @start_code and @end_code are used in /proc/$pid/[stat|statm] output;
- @start_data and @end_data are used in /proc/$pid/[stat|statm] output,
also they are considered if there enough space for brk() syscall
result if RLIMIT_DATA is set;
- @start_brk shown in /proc/$pid/stat output and accounted in brk()
syscall if RLIMIT_DATA is set; also this member is tested to
find a symbolic name of mmap event for perf system (we choose
if event is generated for "heap" area); one more aplication is
selinux -- we test if a process has PROCESS__EXECHEAP permission
if trying to make heap area being executable with mprotect() syscall;
- @brk is a current value for brk() syscall which lays inside heap
area, it's shown in /proc/$pid/stat. When syscall brk() succesfully
provides new memory area to a user space upon brk() completion the
mm::brk is updated to carry new value;
Both @start_brk and @brk are actively used in /proc/$pid/maps
and /proc/$pid/smaps output to find a symbolic name "heap" for
VMA being scanned;
- @start_stack is printed out in /proc/$pid/stat and used to
find a symbolic name "stack" for task and threads in
/proc/$pid/maps and /proc/$pid/smaps output, and as the same
as with @start_brk -- perf system uses it for event naming.
Also kernel treat this member as a start address of where
to map vDSO pages and to check if there is enough space
for shmat() syscall;
- @arg_start, @arg_end, @env_start and @env_end are printed out
in /proc/$pid/stat. Another access to the data these members
represent is to read /proc/$pid/environ or /proc/$pid/cmdline.
Any attempt to read these areas kernel tests with access_process_vm
helper so a user must have enough rights for this action;
- @auxv and @auxv_size may be read from /proc/$pid/auxv. Strictly
speaking kernel doesn't care much about which exactly data is
sitting there because it is solely for userspace;
- @exe_fd is referred from /proc/$pid/exe and when generating
coredump. We uses prctl_set_mm_exe_file_locked helper to update
this member, so exe-file link modification remains one-shot
action.
Still note that updating exe-file link now doesn't require sys-resource
capability anymore, after all there is no much profit in preventing setup
own file link (there are a number of ways to execute own code -- ptrace,
ld-preload, so that the only reliable way to find which exactly code is
executed is to inspect running program memory). Still we require the
caller to be at least user-namespace root user.
I believe the old interface should be deprecated and ripped off in a
couple of kernel releases if no one against.
To test if new interface is implemented in the kernel one can pass
PR_SET_MM_MAP_SIZE opcode and the kernel returns the size of currently
supported struct prctl_mm_map.
[akpm@linux-foundation.org: fix 80-col wordwrap in macro definitions]
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: Tejun Heo <tj@kernel.org>
Acked-by: Andrew Vagin <avagin@openvz.org>
Tested-by: Andrew Vagin <avagin@openvz.org>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
Cc: Pavel Emelyanov <xemul@parallels.com>
Cc: Vasiliy Kulikov <segoon@openwall.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Cc: Julien Tinnes <jln@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
Add VM_INIT_DEF_MASK, to allow us to set the default flags for VMs. It
also adds a prctl control which allows us to set the THP disable bit in
mm->def_flags so that VMs will pick up the setting as they are created.
Signed-off-by: Alex Thorlton <athorlton@sgi.com>
Suggested-by: Oleg Nesterov <oleg@redhat.com>
Cc: Gerald Schaefer <gerald.schaefer@de.ibm.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Mel Gorman <mgorman@suse.de>
Acked-by: Rik van Riel <riel@redhat.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Michael Kerrisk <mtk.manpages@gmail.com>
Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: Dave Jones <davej@redhat.com>
|
|
The documentation didn't actually mention how to enable no_new_privs.
This also adds a note about possible interactions between
no_new_privs and LSMs (i.e. why teaching systemd to set no_new_privs
is not necessarily a good idea), and it references the new docs
from include/linux/prctl.h.
Suggested-by: Rob Landley <rob@landley.net>
Signed-off-by: Andy Lutomirski <luto@amacapital.net>
Acked-by: Kees Cook <keescook@chromium.org>
Signed-off-by: James Morris <james.l.morris@oracle.com>
|
|
Zero is written at clear_tid_address when the process exits. This
functionality is used by pthread_join().
We already have sys_set_tid_address() to change this address for the
current task but there is no way to obtain it from user space.
Without the ability to find this address and dump it we can't restore
pthread'ed apps which call pthread_join() once they have been restored.
This patch introduces the PR_GET_TID_ADDRESS prctl option which allows
the current process to obtain own clear_tid_address.
This feature is available iif CONFIG_CHECKPOINT_RESTORE is set.
[akpm@linux-foundation.org: fix prctl numbering]
Signed-off-by: Andrew Vagin <avagin@openvz.org>
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: Pedro Alves <palves@redhat.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Pavel Emelyanov <xemul@parallels.com>
Cc: Tejun Heo <tj@kernel.org>
Acked-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
When we do restore we would like to have a way to setup a former
mm_struct::exe_file so that /proc/pid/exe would point to the original
executable file a process had at checkpoint time.
For this the PR_SET_MM_EXE_FILE code is introduced. This option takes a
file descriptor which will be set as a source for new /proc/$pid/exe
symlink.
Note it allows to change /proc/$pid/exe if there are no VM_EXECUTABLE
vmas present for current process, simply because this feature is a special
to C/R and mm::num_exe_file_vmas become meaningless after that.
To minimize the amount of transition the /proc/pid/exe symlink might have,
this feature is implemented in one-shot manner. Thus once changed the
symlink can't be changed again. This should help sysadmins to monitor the
symlinks over all process running in a system.
In particular one could make a snapshot of processes and ring alarm if
there unexpected changes of /proc/pid/exe's in a system.
Note -- this feature is available iif CONFIG_CHECKPOINT_RESTORE is set and
the caller must have CAP_SYS_RESOURCE capability granted, otherwise the
request to change symlink will be rejected.
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Reviewed-by: Oleg Nesterov <oleg@redhat.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Pavel Emelyanov <xemul@parallels.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Matt Helsley <matthltc@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
During checkpoint we dump whole process memory to a file and the dump
includes process stack memory. But among stack data itself, the stack
carries additional parameters such as command line arguments, environment
data and auxiliary vector.
So when we do restore procedure and once we've restored stack data itself
we need to setup mm_struct::arg_start/end, env_start/end, so restored
process would be able to find command line arguments and environment data
it had at checkpoint time. The same applies to auxiliary vector.
For this reason additional PR_SET_MM_(ARG_START | ARG_END | ENV_START |
ENV_END | AUXV) codes are introduced.
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Acked-by: Kees Cook <keescook@chromium.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Andrew Vagin <avagin@openvz.org>
Cc: Serge Hallyn <serge.hallyn@canonical.com>
Cc: Pavel Emelyanov <xemul@parallels.com>
Cc: Vasiliy Kulikov <segoon@openwall.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
With this change, calling
prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0)
disables privilege granting operations at execve-time. For example, a
process will not be able to execute a setuid binary to change their uid
or gid if this bit is set. The same is true for file capabilities.
Additionally, LSM_UNSAFE_NO_NEW_PRIVS is defined to ensure that
LSMs respect the requested behavior.
To determine if the NO_NEW_PRIVS bit is set, a task may call
prctl(PR_GET_NO_NEW_PRIVS, 0, 0, 0, 0);
It returns 1 if set and 0 if it is not set. If any of the arguments are
non-zero, it will return -1 and set errno to -EINVAL.
(PR_SET_NO_NEW_PRIVS behaves similarly.)
This functionality is desired for the proposed seccomp filter patch
series. By using PR_SET_NO_NEW_PRIVS, it allows a task to modify the
system call behavior for itself and its child tasks without being
able to impact the behavior of a more privileged task.
Another potential use is making certain privileged operations
unprivileged. For example, chroot may be considered "safe" if it cannot
affect privileged tasks.
Note, this patch causes execve to fail when PR_SET_NO_NEW_PRIVS is
set and AppArmor is in use. It is fixed in a subsequent patch.
Signed-off-by: Andy Lutomirski <luto@amacapital.net>
Signed-off-by: Will Drewry <wad@chromium.org>
Acked-by: Eric Paris <eparis@redhat.com>
Acked-by: Kees Cook <keescook@chromium.org>
v18: updated change desc
v17: using new define values as per 3.4
Signed-off-by: James Morris <james.l.morris@oracle.com>
|
|
Userspace service managers/supervisors need to track their started
services. Many services daemonize by double-forking and get implicitly
re-parented to PID 1. The service manager will no longer be able to
receive the SIGCHLD signals for them, and is no longer in charge of
reaping the children with wait(). All information about the children is
lost at the moment PID 1 cleans up the re-parented processes.
With this prctl, a service manager process can mark itself as a sort of
'sub-init', able to stay as the parent for all orphaned processes
created by the started services. All SIGCHLD signals will be delivered
to the service manager.
Receiving SIGCHLD and doing wait() is in cases of a service-manager much
preferred over any possible asynchronous notification about specific
PIDs, because the service manager has full access to the child process
data in /proc and the PID can not be re-used until the wait(), the
service-manager itself is in charge of, has happened.
As a side effect, the relevant parent PID information does not get lost
by a double-fork, which results in a more elaborate process tree and
'ps' output:
before:
# ps afx
253 ? Ss 0:00 /bin/dbus-daemon --system --nofork
294 ? Sl 0:00 /usr/libexec/polkit-1/polkitd
328 ? S 0:00 /usr/sbin/modem-manager
608 ? Sl 0:00 /usr/libexec/colord
658 ? Sl 0:00 /usr/libexec/upowerd
819 ? Sl 0:00 /usr/libexec/imsettings-daemon
916 ? Sl 0:00 /usr/libexec/udisks-daemon
917 ? S 0:00 \_ udisks-daemon: not polling any devices
after:
# ps afx
294 ? Ss 0:00 /bin/dbus-daemon --system --nofork
426 ? Sl 0:00 \_ /usr/libexec/polkit-1/polkitd
449 ? S 0:00 \_ /usr/sbin/modem-manager
635 ? Sl 0:00 \_ /usr/libexec/colord
705 ? Sl 0:00 \_ /usr/libexec/upowerd
959 ? Sl 0:00 \_ /usr/libexec/udisks-daemon
960 ? S 0:00 | \_ udisks-daemon: not polling any devices
977 ? Sl 0:00 \_ /usr/libexec/packagekitd
This prctl is orthogonal to PID namespaces. PID namespaces are isolated
from each other, while a service management process usually requires the
services to live in the same namespace, to be able to talk to each
other.
Users of this will be the systemd per-user instance, which provides
init-like functionality for the user's login session and D-Bus, which
activates bus services on-demand. Both need init-like capabilities to
be able to properly keep track of the services they start.
Many thanks to Oleg for several rounds of review and insights.
[akpm@linux-foundation.org: fix comment layout and spelling]
[akpm@linux-foundation.org: add lengthy code comment from Oleg]
Reviewed-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Lennart Poettering <lennart@poettering.net>
Signed-off-by: Kay Sievers <kay.sievers@vrfy.org>
Acked-by: Valdis Kletnieks <Valdis.Kletnieks@vt.edu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
For a process to entirely disable Yama ptrace restrictions, it can use
the special PR_SET_PTRACER_ANY pid to indicate that any otherwise allowed
process may ptrace it. This is stronger than calling PR_SET_PTRACER with
pid "1" because it includes processes in external pid namespaces. This is
currently needed by the Chrome renderer, since its crash handler (Breakpad)
runs external to the renderer's pid namespace.
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: James Morris <jmorris@namei.org>
|
|
This adds the Yama Linux Security Module to collect DAC security
improvements (specifically just ptrace restrictions for now) that have
existed in various forms over the years and have been carried outside the
mainline kernel by other Linux distributions like Openwall and grsecurity.
Signed-off-by: Kees Cook <keescook@chromium.org>
Acked-by: John Johansen <john.johansen@canonical.com>
Signed-off-by: James Morris <jmorris@namei.org>
|
|
When we restore a task we need to set up text, data and data heap sizes
from userspace to the values a task had at checkpoint time. This patch
adds auxilary prctl codes for that.
While most of them have a statistical nature (their values are involved
into calculation of /proc/<pid>/statm output) the start_brk and brk values
are used to compute an allowed size of program data segment expansion.
Which means an arbitrary changes of this values might be dangerous
operation. So to restrict access the following requirements applied to
prctl calls:
- The process has to have CAP_SYS_ADMIN capability granted.
- For all opcodes except start_brk/brk members an appropriate
VMA area must exist and should fit certain VMA flags,
such as:
- code segment must be executable but not writable;
- data segment must not be executable.
start_brk/brk values must not intersect with data segment and must not
exceed RLIMIT_DATA resource limit.
Still the main guard is CAP_SYS_ADMIN capability check.
Note the kernel should be compiled with CONFIG_CHECKPOINT_RESTORE support
otherwise these prctl calls will return -EINVAL.
[akpm@linux-foundation.org: cache current->mm in a local, saving 200 bytes text]
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Andrew Vagin <avagin@openvz.org>
Cc: Serge Hallyn <serge.hallyn@canonical.com>
Cc: Pavel Emelyanov <xemul@parallels.com>
Cc: Vasiliy Kulikov <segoon@openwall.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
While writing the manpage I noticed some shortcomings in the
current interface.
- Define symbolic names for all the different values
- Boundary check the kill mode values
- For symmetry add a get interface too. This allows library
code to get/set the current state.
- For consistency define a PR_MCE_KILL_DEFAULT value
Signed-off-by: Andi Kleen <ak@linux.intel.com>
|
|
Bye-bye Performance Counters, welcome Performance Events!
In the past few months the perfcounters subsystem has grown out its
initial role of counting hardware events, and has become (and is
becoming) a much broader generic event enumeration, reporting, logging,
monitoring, analysis facility.
Naming its core object 'perf_counter' and naming the subsystem
'perfcounters' has become more and more of a misnomer. With pending
code like hw-breakpoints support the 'counter' name is less and
less appropriate.
All in one, we've decided to rename the subsystem to 'performance
events' and to propagate this rename through all fields, variables
and API names. (in an ABI compatible fashion)
The word 'event' is also a bit shorter than 'counter' - which makes
it slightly more convenient to write/handle as well.
Thanks goes to Stephane Eranian who first observed this misnomer and
suggested a rename.
User-space tooling and ABI compatibility is not affected - this patch
should be function-invariant. (Also, defconfigs were not touched to
keep the size down.)
This patch has been generated via the following script:
FILES=$(find * -type f | grep -vE 'oprofile|[^K]config')
sed -i \
-e 's/PERF_EVENT_/PERF_RECORD_/g' \
-e 's/PERF_COUNTER/PERF_EVENT/g' \
-e 's/perf_counter/perf_event/g' \
-e 's/nb_counters/nb_events/g' \
-e 's/swcounter/swevent/g' \
-e 's/tpcounter_event/tp_event/g' \
$FILES
for N in $(find . -name perf_counter.[ch]); do
M=$(echo $N | sed 's/perf_counter/perf_event/g')
mv $N $M
done
FILES=$(find . -name perf_event.*)
sed -i \
-e 's/COUNTER_MASK/REG_MASK/g' \
-e 's/COUNTER/EVENT/g' \
-e 's/\<event\>/event_id/g' \
-e 's/counter/event/g' \
-e 's/Counter/Event/g' \
$FILES
... to keep it as correct as possible. This script can also be
used by anyone who has pending perfcounters patches - it converts
a Linux kernel tree over to the new naming. We tried to time this
change to the point in time where the amount of pending patches
is the smallest: the end of the merge window.
Namespace clashes were fixed up in a preparatory patch - and some
stylistic fallout will be fixed up in a subsequent patch.
( NOTE: 'counters' are still the proper terminology when we deal
with hardware registers - and these sed scripts are a bit
over-eager in renaming them. I've undone some of that, but
in case there's something left where 'counter' would be
better than 'event' we can undo that on an individual basis
instead of touching an otherwise nicely automated patch. )
Suggested-by: Stephane Eranian <eranian@google.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Paul Mackerras <paulus@samba.org>
Reviewed-by: Arjan van de Ven <arjan@linux.intel.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: David Howells <dhowells@redhat.com>
Cc: Kyle McMartin <kyle@mcmartin.ca>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: <linux-arch@vger.kernel.org>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
|
|
This allows processes to override their early/late kill
behaviour on hardware memory errors.
Typically applications which are memory error aware is
better of with early kill (see the error as soon
as possible), all others with late kill (only
see the error when the error is really impacting execution)
There's a global sysctl, but this way an application
can set its specific policy.
We're using two bits, one to signify that the process
stated its intention and that
I also made the prctl future proof by enforcing
the unused arguments are 0.
The state is inherited to children.
Note this makes us officially run out of process flags
on 32bit, but the next patch can easily add another field.
Manpage patch will be supplied separately.
Signed-off-by: Andi Kleen <ak@linux.intel.com>
|
|
Add a way for self-monitoring tasks to disable/enable counters summarily,
via a prctl:
PR_TASK_PERF_COUNTERS_DISABLE 31
PR_TASK_PERF_COUNTERS_ENABLE 32
Signed-off-by: Ingo Molnar <mingo@elte.hu>
|
|
We want to be able to control the default "rounding" that is used by
select() and poll() and friends. This is a per process property
(so that we can have a "nice" like program to start certain programs with
a looser or stricter rounding) that can be set/get via a prctl().
For this purpose, a field called "timer_slack_ns" is added to the task
struct. In addition, a field called "default_timer_slack"ns" is added
so that tasks easily can temporarily to a more/less accurate slack and then
back to the default.
The default value of the slack is set to 50 usec; this is significantly less
than 2.6.27's average select() and poll() timing error but still allows
the kernel to group timers somewhat to preserve power behavior. Applications
and admins can override this via the prctl()
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
|
|
Filesystem capability support makes it possible to do away with (set)uid-0
based privilege and use capabilities instead. That is, with filesystem
support for capabilities but without this present patch, it is (conceptually)
possible to manage a system with capabilities alone and never need to obtain
privilege via (set)uid-0.
Of course, conceptually isn't quite the same as currently possible since few
user applications, certainly not enough to run a viable system, are currently
prepared to leverage capabilities to exercise privilege. Further, many
applications exist that may never get upgraded in this way, and the kernel
will continue to want to support their setuid-0 base privilege needs.
Where pure-capability applications evolve and replace setuid-0 binaries, it is
desirable that there be a mechanisms by which they can contain their
privilege. In addition to leveraging the per-process bounding and inheritable
sets, this should include suppressing the privilege of the uid-0 superuser
from the process' tree of children.
The feature added by this patch can be leveraged to suppress the privilege
associated with (set)uid-0. This suppression requires CAP_SETPCAP to
initiate, and only immediately affects the 'current' process (it is inherited
through fork()/exec()). This reimplementation differs significantly from the
historical support for securebits which was system-wide, unwieldy and which
has ultimately withered to a dead relic in the source of the modern kernel.
With this patch applied a process, that is capable(CAP_SETPCAP), can now drop
all legacy privilege (through uid=0) for itself and all subsequently
fork()'d/exec()'d children with:
prctl(PR_SET_SECUREBITS, 0x2f);
This patch represents a no-op unless CONFIG_SECURITY_FILE_CAPABILITIES is
enabled at configure time.
[akpm@linux-foundation.org: fix uninitialised var warning]
[serue@us.ibm.com: capabilities: use cap_task_prctl when !CONFIG_SECURITY]
Signed-off-by: Andrew G. Morgan <morgan@kernel.org>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Reviewed-by: James Morris <jmorris@namei.org>
Cc: Stephen Smalley <sds@tycho.nsa.gov>
Cc: Paul Moore <paul.moore@hp.com>
Signed-off-by: Serge E. Hallyn <serue@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
This patch adds prctl commands that make it possible
to deny the execution of timestamp counters in userspace.
If this is not implemented on a specific architecture,
prctl will return -EINVAL.
ned-off-by: Erik Bosman <ejbosman@cs.vu.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
|
|
The capability bounding set is a set beyond which capabilities cannot grow.
Currently cap_bset is per-system. It can be manipulated through sysctl,
but only init can add capabilities. Root can remove capabilities. By
default it includes all caps except CAP_SETPCAP.
This patch makes the bounding set per-process when file capabilities are
enabled. It is inherited at fork from parent. Noone can add elements,
CAP_SETPCAP is required to remove them.
One example use of this is to start a safer container. For instance, until
device namespaces or per-container device whitelists are introduced, it is
best to take CAP_MKNOD away from a container.
The bounding set will not affect pP and pE immediately. It will only
affect pP' and pE' after subsequent exec()s. It also does not affect pI,
and exec() does not constrain pI'. So to really start a shell with no way
of regain CAP_MKNOD, you would do
prctl(PR_CAPBSET_DROP, CAP_MKNOD);
cap_t cap = cap_get_proc();
cap_value_t caparray[1];
caparray[0] = CAP_MKNOD;
cap_set_flag(cap, CAP_INHERITABLE, 1, caparray, CAP_DROP);
cap_set_proc(cap);
cap_free(cap);
The following test program will get and set the bounding
set (but not pI). For instance
./bset get
(lists capabilities in bset)
./bset drop cap_net_raw
(starts shell with new bset)
(use capset, setuid binary, or binary with
file capabilities to try to increase caps)
************************************************************
cap_bound.c
************************************************************
#include <sys/prctl.h>
#include <linux/capability.h>
#include <sys/types.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#ifndef PR_CAPBSET_READ
#define PR_CAPBSET_READ 23
#endif
#ifndef PR_CAPBSET_DROP
#define PR_CAPBSET_DROP 24
#endif
int usage(char *me)
{
printf("Usage: %s get\n", me);
printf(" %s drop <capability>\n", me);
return 1;
}
#define numcaps 32
char *captable[numcaps] = {
"cap_chown",
"cap_dac_override",
"cap_dac_read_search",
"cap_fowner",
"cap_fsetid",
"cap_kill",
"cap_setgid",
"cap_setuid",
"cap_setpcap",
"cap_linux_immutable",
"cap_net_bind_service",
"cap_net_broadcast",
"cap_net_admin",
"cap_net_raw",
"cap_ipc_lock",
"cap_ipc_owner",
"cap_sys_module",
"cap_sys_rawio",
"cap_sys_chroot",
"cap_sys_ptrace",
"cap_sys_pacct",
"cap_sys_admin",
"cap_sys_boot",
"cap_sys_nice",
"cap_sys_resource",
"cap_sys_time",
"cap_sys_tty_config",
"cap_mknod",
"cap_lease",
"cap_audit_write",
"cap_audit_control",
"cap_setfcap"
};
int getbcap(void)
{
int comma=0;
unsigned long i;
int ret;
printf("i know of %d capabilities\n", numcaps);
printf("capability bounding set:");
for (i=0; i<numcaps; i++) {
ret = prctl(PR_CAPBSET_READ, i);
if (ret < 0)
perror("prctl");
else if (ret==1)
printf("%s%s", (comma++) ? ", " : " ", captable[i]);
}
printf("\n");
return 0;
}
int capdrop(char *str)
{
unsigned long i;
int found=0;
for (i=0; i<numcaps; i++) {
if (strcmp(captable[i], str) == 0) {
found=1;
break;
}
}
if (!found)
return 1;
if (prctl(PR_CAPBSET_DROP, i)) {
perror("prctl");
return 1;
}
return 0;
}
int main(int argc, char *argv[])
{
if (argc<2)
return usage(argv[0]);
if (strcmp(argv[1], "get")==0)
return getbcap();
if (strcmp(argv[1], "drop")!=0 || argc<3)
return usage(argv[0]);
if (capdrop(argv[2])) {
printf("unknown capability\n");
return 1;
}
return execl("/bin/bash", "/bin/bash", NULL);
}
************************************************************
[serue@us.ibm.com: fix typo]
Signed-off-by: Serge E. Hallyn <serue@us.ibm.com>
Signed-off-by: Andrew G. Morgan <morgan@kernel.org>
Cc: Stephen Smalley <sds@tycho.nsa.gov>
Cc: James Morris <jmorris@namei.org>
Cc: Chris Wright <chrisw@sous-sol.org>
Cc: Casey Schaufler <casey@schaufler-ca.com>a
Signed-off-by: "Serge E. Hallyn" <serue@us.ibm.com>
Tested-by: Jiri Slaby <jirislaby@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
This reduces the memory footprint and it enforces that only the current
task can enable seccomp on itself (this is a requirement for a
strightforward [modulo preempt ;) ] TIF_NOTSC implementation).
Signed-off-by: Andrea Arcangeli <andrea@cpushare.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
This new prctl is intended for changing the execution mode of the
processor, on processors that support both a little-endian mode and a
big-endian mode. It is intended for use by programs such as
instruction set emulators (for example an x86 emulator on PowerPC),
which may find it convenient to use the processor in an alternate
endianness mode when executing translated instructions.
Note that this does not imply the existence of a fully-fledged ABI for
both endiannesses, or of compatibility code for converting system
calls done in the non-native endianness mode. The program is expected
to arrange for all of its system call arguments to be presented in the
native endianness.
Switching between big and little-endian mode will require some care in
constructing the instruction sequence for the switch. Generally the
instructions up to the instruction that invokes the prctl system call
will have to be in the old endianness, and subsequent instructions
will have to be in the new endianness.
Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>
|
