From: Ravi Bangoria Date: Tue, 11 Apr 2017 05:08:13 +0000 (+0530) Subject: powerpc/kprobe: Fix oops when kprobed on 'stdu' instruction X-Git-Tag: v4.11-rc8~6^2~1 X-Git-Url: https://asedeno.scripts.mit.edu/gitweb/?a=commitdiff_plain;h=9e1ba4f27f018742a1aa95d11e35106feba08ec1;p=linux.git powerpc/kprobe: Fix oops when kprobed on 'stdu' instruction If we set a kprobe on a 'stdu' instruction on powerpc64, we see a kernel OOPS: Bad kernel stack pointer cd93c840 at c000000000009868 Oops: Bad kernel stack pointer, sig: 6 [#1] ... GPR00: c000001fcd93cb30 00000000cd93c840 c0000000015c5e00 00000000cd93c840 ... NIP [c000000000009868] resume_kernel+0x2c/0x58 LR [c000000000006208] program_check_common+0x108/0x180 On a 64-bit system when the user probes on a 'stdu' instruction, the kernel does not emulate actual store in emulate_step() because it may corrupt the exception frame. So the kernel does the actual store operation in exception return code i.e. resume_kernel(). resume_kernel() loads the saved stack pointer from memory using lwz, which only loads the low 32-bits of the address, causing the kernel crash. Fix this by loading the 64-bit value instead. Fixes: be96f63375a1 ("powerpc: Split out instruction analysis part of emulate_step()") Cc: stable@vger.kernel.org # v3.18+ Signed-off-by: Ravi Bangoria Reviewed-by: Naveen N. Rao Reviewed-by: Ananth N Mavinakayanahalli [mpe: Change log massage, add stable tag] Signed-off-by: Michael Ellerman --- diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S index 6432d4bf08c8..767ef6d68c9e 100644 --- a/arch/powerpc/kernel/entry_64.S +++ b/arch/powerpc/kernel/entry_64.S @@ -689,7 +689,7 @@ resume_kernel: addi r8,r1,INT_FRAME_SIZE /* Get the kprobed function entry */ - lwz r3,GPR1(r1) + ld r3,GPR1(r1) subi r3,r3,INT_FRAME_SIZE /* dst: Allocate a trampoline exception frame */ mr r4,r1 /* src: current exception frame */ mr r1,r3 /* Reroute the trampoline frame to r1 */ @@ -703,8 +703,8 @@ resume_kernel: addi r6,r6,8 bdnz 2b - /* Do real store operation to complete stwu */ - lwz r5,GPR1(r1) + /* Do real store operation to complete stdu */ + ld r5,GPR1(r1) std r8,0(r5) /* Clear _TIF_EMULATE_STACK_STORE flag */