From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sasha Levin Subject: [PATCH AUTOSEL for 4.4 004/167] x86/asm: Don't use RBP as a temporary register in csum_partial_copy_generic() Date: Mon, 19 Mar 2018 16:05:24 +0000 Message-ID: <20180319160513.16384-4-alexander.levin@microsoft.com> References: <20180319160513.16384-1-alexander.levin@microsoft.com> Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Cc: Josh Poimboeuf , Cong Wang , "David S . Miller" , Dmitry Vyukov , Eric Dumazet , Kostya Serebryany , Linus Torvalds , Marcelo Ricardo Leitner , Neil Horman , Peter Zijlstra , Thomas Gleixner , Vlad Yasevich , "linux-sctp@vger.kernel.org" , netdev , syzkaller , Ingo Molnar , Sasha Levin To: "linux-kernel@vger.kernel.org" , "stable@vger.kernel.org" Return-path: In-Reply-To: <20180319160513.16384-1-alexander.levin@microsoft.com> Content-Language: en-US Sender: stable-owner@vger.kernel.org List-Id: netdev.vger.kernel.org From: Josh Poimboeuf [ Upstream commit 42fc6c6cb1662ba2fa727dd01c9473c63be4e3b6 ] Andrey Konovalov reported the following warning while fuzzing the kernel with syzkaller: WARNING: kernel stack regs at ffff8800686869f8 in a.out:4933 has bad 'bp'= value c3fc855a10167ec0 The unwinder dump revealed that RBP had a bad value when an interrupt occurred in csum_partial_copy_generic(). That function saves RBP on the stack and then overwrites it, using it as a scratch register. That's problematic because it breaks stack traces if an interrupt occurs in the middle of the function. Replace the usage of RBP with another callee-saved register (R15) so stack traces are no longer affected. Reported-by: Andrey Konovalov Tested-by: Andrey Konovalov Signed-off-by: Josh Poimboeuf Cc: Cong Wang Cc: David S . Miller Cc: Dmitry Vyukov Cc: Eric Dumazet Cc: Kostya Serebryany Cc: Linus Torvalds Cc: Marcelo Ricardo Leitner Cc: Neil Horman Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: Vlad Yasevich Cc: linux-sctp@vger.kernel.org Cc: netdev Cc: syzkaller Link: http://lkml.kernel.org/r/4b03a961efda5ec9bfe46b7b9c9ad72d1efad343.149= 3909486.git.jpoimboe@redhat.com Signed-off-by: Ingo Molnar Signed-off-by: Sasha Levin --- arch/x86/lib/csum-copy_64.S | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) diff --git a/arch/x86/lib/csum-copy_64.S b/arch/x86/lib/csum-copy_64.S index 7e48807b2fa1..45a53dfe1859 100644 --- a/arch/x86/lib/csum-copy_64.S +++ b/arch/x86/lib/csum-copy_64.S @@ -55,7 +55,7 @@ ENTRY(csum_partial_copy_generic) movq %r12, 3*8(%rsp) movq %r14, 4*8(%rsp) movq %r13, 5*8(%rsp) - movq %rbp, 6*8(%rsp) + movq %r15, 6*8(%rsp) =20 movq %r8, (%rsp) movq %r9, 1*8(%rsp) @@ -74,7 +74,7 @@ ENTRY(csum_partial_copy_generic) /* main loop. clear in 64 byte blocks */ /* r9: zero, r8: temp2, rbx: temp1, rax: sum, rcx: saved length */ /* r11: temp3, rdx: temp4, r12 loopcnt */ - /* r10: temp5, rbp: temp6, r14 temp7, r13 temp8 */ + /* r10: temp5, r15: temp6, r14 temp7, r13 temp8 */ .p2align 4 .Lloop: source @@ -89,7 +89,7 @@ ENTRY(csum_partial_copy_generic) source movq 32(%rdi), %r10 source - movq 40(%rdi), %rbp + movq 40(%rdi), %r15 source movq 48(%rdi), %r14 source @@ -103,7 +103,7 @@ ENTRY(csum_partial_copy_generic) adcq %r11, %rax adcq %rdx, %rax adcq %r10, %rax - adcq %rbp, %rax + adcq %r15, %rax adcq %r14, %rax adcq %r13, %rax =20 @@ -121,7 +121,7 @@ ENTRY(csum_partial_copy_generic) dest movq %r10, 32(%rsi) dest - movq %rbp, 40(%rsi) + movq %r15, 40(%rsi) dest movq %r14, 48(%rsi) dest @@ -203,7 +203,7 @@ ENTRY(csum_partial_copy_generic) movq 3*8(%rsp), %r12 movq 4*8(%rsp), %r14 movq 5*8(%rsp), %r13 - movq 6*8(%rsp), %rbp + movq 6*8(%rsp), %r15 addq $7*8, %rsp ret =20 --=20 2.14.1