This is a note to let you know that I've just added the patch titled

    x86/asm: Don't use RBP as a temporary register in 

to the 4.4-stable tree which can be found at:;a=summary

The filename of the patch is:
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <> know about it.

>From foo@baz Tue Apr 10 10:31:53 CEST 2018
From: Josh Poimboeuf <>
Date: Thu, 4 May 2017 09:51:40 -0500
Subject: x86/asm: Don't use RBP as a temporary register in 

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: netdev <>
Cc: syzkaller <>
Signed-off-by: Ingo Molnar <>
Signed-off-by: Sasha Levin <>
Signed-off-by: Greg Kroah-Hartman <>
 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
@@ -89,7 +89,7 @@ ENTRY(csum_partial_copy_generic)
        movq  32(%rdi), %r10
-       movq  40(%rdi), %rbp
+       movq  40(%rdi), %r15
        movq  48(%rdi), %r14
@@ -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)
        movq %r10, 32(%rsi)
-       movq %rbp, 40(%rsi)
+       movq %r15, 40(%rsi)
        movq %r14, 48(%rsi)
@@ -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

Patches currently in stable-queue which might be from are


Reply via email to