Commit-ID: 42fc6c6cb1662ba2fa727dd01c9473c63be4e3b6 Gitweb: http://git.kernel.org/tip/42fc6c6cb1662ba2fa727dd01c9473c63be4e3b6 Author: Josh Poimboeuf <jpoim...@redhat.com> AuthorDate: Thu, 4 May 2017 09:51:40 -0500 Committer: Ingo Molnar <mi...@kernel.org> CommitDate: Fri, 5 May 2017 07:59:24 +0200
x86/asm: Don't use RBP as a temporary register in csum_partial_copy_generic() 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 <andreyk...@google.com> Tested-by: Andrey Konovalov <andreyk...@google.com> Signed-off-by: Josh Poimboeuf <jpoim...@redhat.com> Cc: Cong Wang <xiyou.wangc...@gmail.com> Cc: David S . Miller <da...@davemloft.net> Cc: Dmitry Vyukov <dvyu...@google.com> Cc: Eric Dumazet <eduma...@google.com> Cc: Kostya Serebryany <k...@google.com> Cc: Linus Torvalds <torva...@linux-foundation.org> Cc: Marcelo Ricardo Leitner <marcelo.leit...@gmail.com> Cc: Neil Horman <nhor...@tuxdriver.com> Cc: Peter Zijlstra <pet...@infradead.org> Cc: Thomas Gleixner <t...@linutronix.de> Cc: Vlad Yasevich <vyasev...@gmail.com> Cc: linux-s...@vger.kernel.org Cc: netdev <net...@vger.kernel.org> Cc: syzkaller <syzkal...@googlegroups.com> Link: http://lkml.kernel.org/r/4b03a961efda5ec9bfe46b7b9c9ad72d1efad343.1493909486.git.jpoim...@redhat.com Signed-off-by: Ingo Molnar <mi...@kernel.org> --- 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 7e48807..45a53df 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) 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 @@ -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
