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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 <andreyknvl@google.com> Tested-by: Andrey Konovalov <andreyknvl@google.com> Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Cong Wang <xiyou.wangcong@gmail.com> Cc: David S . Miller <davem@davemloft.net> Cc: Dmitry Vyukov <dvyukov@google.com> Cc: Eric Dumazet <edumazet@google.com> Cc: Kostya Serebryany <kcc@google.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com> Cc: Neil Horman <nhorman@tuxdriver.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Vlad Yasevich <vyasevich@gmail.com> Cc: linux-sctp@vger.kernel.org Cc: netdev <netdev@vger.kernel.org> Cc: syzkaller <syzkaller@googlegroups.com> Link: http://lkml.kernel.org/r/4b03a961efda5ec9bfe46b7b9c9ad72d1efad343.1493909486.git.jpoimboe@redhat.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
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1 changed files with 6 additions and 6 deletions
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@ -55,7 +55,7 @@ ENTRY(csum_partial_copy_generic)
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movq %r12, 3*8(%rsp)
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movq %r12, 3*8(%rsp)
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movq %r14, 4*8(%rsp)
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movq %r14, 4*8(%rsp)
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movq %r13, 5*8(%rsp)
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movq %r13, 5*8(%rsp)
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movq %rbp, 6*8(%rsp)
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movq %r15, 6*8(%rsp)
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movq %r8, (%rsp)
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movq %r8, (%rsp)
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movq %r9, 1*8(%rsp)
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movq %r9, 1*8(%rsp)
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@ -74,7 +74,7 @@ ENTRY(csum_partial_copy_generic)
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/* main loop. clear in 64 byte blocks */
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/* main loop. clear in 64 byte blocks */
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/* r9: zero, r8: temp2, rbx: temp1, rax: sum, rcx: saved length */
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/* r9: zero, r8: temp2, rbx: temp1, rax: sum, rcx: saved length */
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/* r11: temp3, rdx: temp4, r12 loopcnt */
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/* r11: temp3, rdx: temp4, r12 loopcnt */
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/* r10: temp5, rbp: temp6, r14 temp7, r13 temp8 */
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/* r10: temp5, r15: temp6, r14 temp7, r13 temp8 */
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.p2align 4
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.p2align 4
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.Lloop:
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.Lloop:
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source
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source
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@ -89,7 +89,7 @@ ENTRY(csum_partial_copy_generic)
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source
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source
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movq 32(%rdi), %r10
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movq 32(%rdi), %r10
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source
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source
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movq 40(%rdi), %rbp
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movq 40(%rdi), %r15
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source
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source
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movq 48(%rdi), %r14
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movq 48(%rdi), %r14
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source
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source
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@ -103,7 +103,7 @@ ENTRY(csum_partial_copy_generic)
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adcq %r11, %rax
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adcq %r11, %rax
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adcq %rdx, %rax
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adcq %rdx, %rax
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adcq %r10, %rax
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adcq %r10, %rax
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adcq %rbp, %rax
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adcq %r15, %rax
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adcq %r14, %rax
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adcq %r14, %rax
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adcq %r13, %rax
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adcq %r13, %rax
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@ -121,7 +121,7 @@ ENTRY(csum_partial_copy_generic)
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dest
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dest
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movq %r10, 32(%rsi)
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movq %r10, 32(%rsi)
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dest
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dest
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movq %rbp, 40(%rsi)
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movq %r15, 40(%rsi)
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dest
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dest
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movq %r14, 48(%rsi)
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movq %r14, 48(%rsi)
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dest
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dest
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@ -203,7 +203,7 @@ ENTRY(csum_partial_copy_generic)
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movq 3*8(%rsp), %r12
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movq 3*8(%rsp), %r12
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movq 4*8(%rsp), %r14
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movq 4*8(%rsp), %r14
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movq 5*8(%rsp), %r13
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movq 5*8(%rsp), %r13
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movq 6*8(%rsp), %rbp
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movq 6*8(%rsp), %r15
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addq $7*8, %rsp
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addq $7*8, %rsp
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ret
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ret
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