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| author | Michael Neuling <mikey@neuling.org> | 2013-12-16 15:12:43 +1100 |
|---|---|---|
| committer | Ben Hutchings <ben@decadent.org.uk> | 2014-02-15 19:20:16 +0000 |
| commit | c58ad1af9efe5fedc1e35362e53d4329a9e288e7 (patch) | |
| tree | 9fee75b929e1824ce193759a4534371a7748fcac /arch | |
| parent | d9bd24c3bc422acf43f744124d6537921719352f (diff) | |
| download | lwn-c58ad1af9efe5fedc1e35362e53d4329a9e288e7.tar.gz lwn-c58ad1af9efe5fedc1e35362e53d4329a9e288e7.zip | |
powerpc: Fix bad stack check in exception entry
commit 90ff5d688e61f49f23545ffab6228bd7e87e6dc7 upstream.
In EXCEPTION_PROLOG_COMMON() we check to see if the stack pointer (r1)
is valid when coming from the kernel. If it's not valid, we die but
with a nice oops message.
Currently we allocate a stack frame (subtract INT_FRAME_SIZE) before we
check to see if the stack pointer is negative. Unfortunately, this
won't detect a bad stack where r1 is less than INT_FRAME_SIZE.
This patch fixes the check to compare the modified r1 with
-INT_FRAME_SIZE. With this, bad kernel stack pointers (including NULL
pointers) are correctly detected again.
Kudos to Paulus for finding this.
Signed-off-by: Michael Neuling <mikey@neuling.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/powerpc/include/asm/exception-64s.h | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/arch/powerpc/include/asm/exception-64s.h b/arch/powerpc/include/asm/exception-64s.h index 8057f4f6980f..da85ad4254f4 100644 --- a/arch/powerpc/include/asm/exception-64s.h +++ b/arch/powerpc/include/asm/exception-64s.h @@ -163,7 +163,7 @@ do_kvm_##n: \ subi r1,r1,INT_FRAME_SIZE; /* alloc frame on kernel stack */ \ beq- 1f; \ ld r1,PACAKSAVE(r13); /* kernel stack to use */ \ -1: cmpdi cr1,r1,0; /* check if r1 is in userspace */ \ +1: cmpdi cr1,r1,-INT_FRAME_SIZE; /* check if r1 is in userspace */ \ blt+ cr1,3f; /* abort if it is */ \ li r1,(n); /* will be reloaded later */ \ sth r1,PACA_TRAP_SAVE(r13); \ |