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x86/entry/64: Fix stack return address retrieval in thunk

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With CONFIG_FRAME_POINTER enabled, a thunk can pass a bad return address
value to the called function.  '9*8(%rsp)' actually gets the frame
pointer, not the return address.

The only users of the 'put_ret_addr_in_rdi' option are two functions
which trace the enabling and disabling of interrupts, so this bug can
result in bad debug or tracing information with CONFIG_IRQSOFF_TRACER or
CONFIG_PROVE_LOCKING.

Fix this by implementing the suggestion of Linus: explicitly push
the frame pointer all the time and constify the stack offsets that
way. This is both correct and easier to read.

Reported-by: Matt Fleming <matt@codeblueprint.co.uk>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
[ Extended the changelog a bit. ]
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Alex Thorlton <athorlton@sgi.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Fixes: 058fb73274f9 ("x86/asm/entry: Create stack frames in thunk functions")
Link: http://lkml.kernel.org/r/20160517180606.v5o7wcgdni7443ol@treble
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Josh Poimboeuf 2016-05-17 13:06:06 -05:00 committed by Ingo Molnar
parent 683ad8092c
commit d4bf7078c4
1 changed files with 5 additions and 6 deletions
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11
arch/x86/entry/thunk_64.S
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@ -8,16 +8,15 @@
#include <linux/linkage.h>
#include "calling.h"
#include <asm/asm.h>
#include <asm/frame.h>
/* rdi: arg1 ... normal C conventions. rax is saved/restored. */
.macro THUNK name, func, put_ret_addr_in_rdi=0
.globl \name
.type \name, @function
\name:
FRAME_BEGIN
pushq %rbp
movq %rsp, %rbp
/* this one pushes 9 elems, the next one would be %rIP */
pushq %rdi
pushq %rsi
pushq %rdx
@ -29,8 +28,8 @@
pushq %r11
.if \put_ret_addr_in_rdi
/* 9*8(%rsp) is return addr on stack */
movq 9*8(%rsp), %rdi
/* 8(%rbp) is return addr on stack */
movq 8(%rbp), %rdi
.endif
call \func
@ -65,7 +64,7 @@ restore:
popq %rdx
popq %rsi
popq %rdi
FRAME_END
popq %rbp
ret
_ASM_NOKPROBE(restore)
#endif