| From foo@baz Mon Apr 9 17:09:24 CEST 2018 |
| From: Josh Poimboeuf <jpoimboe@redhat.com> |
| Date: Thu, 4 May 2017 09:51:40 -0500 |
| Subject: x86/asm: Don't use RBP as a temporary register in csum_partial_copy_generic() |
| |
| From: Josh Poimboeuf <jpoimboe@redhat.com> |
| |
| |
| [ 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 <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> |
| Signed-off-by: Sasha Levin <alexander.levin@microsoft.com> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| --- |
| arch/x86/lib/csum-copy_64.S | 12 ++++++------ |
| 1 file changed, 6 insertions(+), 6 deletions(-) |
| |
| --- 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 |
| |