diff options
| author | Mark Rutland <mark.rutland@arm.com> | 2016-10-11 13:51:27 -0700 |
|---|---|---|
| committer | Sami Tolvanen <samitolvanen@google.com> | 2016-10-18 11:08:46 -0700 |
| commit | 7af6188c36382c1a11551cf8bea62bcb3dcaa585 (patch) | |
| tree | 896dca8fdc5106304882401fc9418dbf6e925d2f | |
| parent | 140cab831036741cac88255f282cd68b72140356 (diff) | |
BACKPORT: lib: harden strncpy_from_user
The strncpy_from_user() accessor is effectively a copy_from_user()
specialised to copy strings, terminating early at a NUL byte if possible.
In other respects it is identical, and can be used to copy an arbitrarily
large buffer from userspace into the kernel. Conceptually, it exposes a
similar attack surface.
As with copy_from_user(), we check the destination range when the kernel
is built with KASAN, but unlike copy_from_user() we do not check the
destination buffer when using HARDENED_USERCOPY. As strncpy_from_user()
calls get_user() in a loop, we must call check_object_size() explicitly.
This patch adds this instrumentation to strncpy_from_user(), per the same
rationale as with the regular copy_from_user(). In the absence of
hardened usercopy this will have no impact as the instrumentation expands
to an empty static inline function.
Link: http://lkml.kernel.org/r/1472221903-31181-1-git-send-email-mark.rutland@arm.com
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Kees Cook <keescook@chromium.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Bug: 31374226
Change-Id: I898e4e9f19307e37a9be497cb1a0d7f1e3911661
(cherry picked from commit bf90e56e467ed5766722972d483e6711889ed1b0)
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
| -rw-r--r-- | lib/strncpy_from_user.c | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/lib/strncpy_from_user.c b/lib/strncpy_from_user.c index 5a003a2ebd96..05efc1fa97f0 100644 --- a/lib/strncpy_from_user.c +++ b/lib/strncpy_from_user.c @@ -1,5 +1,6 @@ #include <linux/compiler.h> #include <linux/export.h> +#include <linux/thread_info.h> #include <linux/uaccess.h> #include <linux/kernel.h> #include <linux/errno.h> @@ -109,6 +110,7 @@ long strncpy_from_user(char *dst, const char __user *src, long count) unsigned long max = max_addr - src_addr; long retval; + check_object_size(dst, count, false); user_access_begin(); retval = do_strncpy_from_user(dst, src, count, max); user_access_end(); |