From 4a6b27b79da5ccc6b85dc05bbe6a091e58be896a Mon Sep 17 00:00:00 2001 From: Josh Poimboeuf Date: Mon, 16 May 2016 15:16:18 -0500 Subject: [PATCH] crypto: sha1-mb - make sha1_x8_avx2() conform to C function ABI Megha Dey reported a kernel panic in crypto code. The problem is that sha1_x8_avx2() clobbers registers r12-r15 without saving and restoring them. Before commit aec4d0e301f1 ("x86/asm/crypto: Simplify stack usage in sha-mb functions"), those registers were saved and restored by the callers of the function. I removed them with that commit because I didn't realize sha1_x8_avx2() clobbered them. Fix the potential undefined behavior associated with clobbering the registers and make the behavior less surprising by changing the registers to be callee saved/restored to conform with the C function call ABI. Also, rdx (aka RSP_SAVE) doesn't need to be saved: I verified that none of the callers rely on it being saved, and it's not a callee-saved register in the C ABI. Fixes: aec4d0e301f1 ("x86/asm/crypto: Simplify stack usage in sha-mb functions") Cc: stable@vger.kernel.org # 4.6 Reported-by: Megha Dey Signed-off-by: Josh Poimboeuf Signed-off-by: Herbert Xu --- arch/x86/crypto/sha-mb/sha1_x8_avx2.S | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-) diff --git a/arch/x86/crypto/sha-mb/sha1_x8_avx2.S b/arch/x86/crypto/sha-mb/sha1_x8_avx2.S index 8e1b47792b31..c9dae1cd2919 100644 --- a/arch/x86/crypto/sha-mb/sha1_x8_avx2.S +++ b/arch/x86/crypto/sha-mb/sha1_x8_avx2.S @@ -296,7 +296,11 @@ W14 = TMP_ # ENTRY(sha1_x8_avx2) - push RSP_SAVE + # save callee-saved clobbered registers to comply with C function ABI + push %r12 + push %r13 + push %r14 + push %r15 #save rsp mov %rsp, RSP_SAVE @@ -446,7 +450,12 @@ lloop: ## Postamble mov RSP_SAVE, %rsp - pop RSP_SAVE + + # restore callee-saved clobbered registers + pop %r15 + pop %r14 + pop %r13 + pop %r12 ret ENDPROC(sha1_x8_avx2)