diff options
| author | Michael Neuling <mikey@neuling.org> | 2019-04-22 00:20:29 +1000 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2019-05-16 19:44:50 +0200 |
| commit | 7fe905d0973eee071ebc4861cd6d23138116cd9e (patch) | |
| tree | ba0f8022f7450853fcba84209c8eb0cb14de362e /arch/powerpc/lib/code-patching.c | |
| parent | ee1a6e164cacaff82e149e97b029515a4a2ffb2e (diff) | |
powerpc: Avoid code patching freed init sections
commit 51c3c62b58b357e8d35e4cc32f7b4ec907426fe3 upstream.
This stops us from doing code patching in init sections after they've
been freed.
In this chain:
kvm_guest_init() ->
kvm_use_magic_page() ->
fault_in_pages_readable() ->
__get_user() ->
__get_user_nocheck() ->
barrier_nospec();
We have a code patching location at barrier_nospec() and
kvm_guest_init() is an init function. This whole chain gets inlined,
so when we free the init section (hence kvm_guest_init()), this code
goes away and hence should no longer be patched.
We seen this as userspace memory corruption when using a memory
checker while doing partition migration testing on powervm (this
starts the code patching post migration via
/sys/kernel/mobility/migration). In theory, it could also happen when
using /sys/kernel/debug/powerpc/barrier_nospec.
Signed-off-by: Michael Neuling <mikey@neuling.org>
Reviewed-by: Nicholas Piggin <npiggin@gmail.com>
Reviewed-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'arch/powerpc/lib/code-patching.c')
| -rw-r--r-- | arch/powerpc/lib/code-patching.c | 13 |
1 files changed, 13 insertions, 0 deletions
diff --git a/arch/powerpc/lib/code-patching.c b/arch/powerpc/lib/code-patching.c index 2ce6159d8983..570c06a00db6 100644 --- a/arch/powerpc/lib/code-patching.c +++ b/arch/powerpc/lib/code-patching.c @@ -14,12 +14,25 @@ #include <asm/page.h> #include <asm/code-patching.h> #include <asm/uaccess.h> +#include <asm/setup.h> +#include <asm/sections.h> +static inline bool is_init(unsigned int *addr) +{ + return addr >= (unsigned int *)__init_begin && addr < (unsigned int *)__init_end; +} + int patch_instruction(unsigned int *addr, unsigned int instr) { int err; + /* Make sure we aren't patching a freed init section */ + if (init_mem_is_free && is_init(addr)) { + pr_debug("Skipping init section patching addr: 0x%px\n", addr); + return 0; + } + __put_user_size(instr, addr, 4, err); if (err) return err; |