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x86/unwind: Silence more entry-code related warnings 

Borislav Petkov reported the following unwinder warning:

  WARNING: kernel stack regs at ffffc9000024fea8 in udevadm:92 has bad 'bp' value 00007fffc4614d30
  unwind stack type:0 next_sp:          (null) mask:0x6 graph_idx:0
  ffffc9000024fea8: 000055a6100e9b38 (0x55a6100e9b38)
  ffffc9000024feb0: 000055a6100e9b35 (0x55a6100e9b35)
  ffffc9000024feb8: 000055a6100e9f68 (0x55a6100e9f68)
  ffffc9000024fec0: 000055a6100e9f50 (0x55a6100e9f50)
  ffffc9000024fec8: 00007fffc4614d30 (0x7fffc4614d30)
  ffffc9000024fed0: 000055a6100eaf50 (0x55a6100eaf50)
  ffffc9000024fed8: 0000000000000000 ...
  ffffc9000024fee0: 0000000000000100 (0x100)
  ffffc9000024fee8: ffff8801187df488 (0xffff8801187df488)
  ffffc9000024fef0: 00007ffffffff000 (0x7ffffffff000)
  ffffc9000024fef8: 0000000000000000 ...
  ffffc9000024ff10: ffffc9000024fe98 (0xffffc9000024fe98)
  ffffc9000024ff18: 00007fffc4614d00 (0x7fffc4614d00)
  ffffc9000024ff20: ffffffffffffff10 (0xffffffffffffff10)
  ffffc9000024ff28: ffffffff811c6c1f (SyS_newlstat+0xf/0x10)
  ffffc9000024ff30: 0000000000000010 (0x10)
  ffffc9000024ff38: 0000000000000296 (0x296)
  ffffc9000024ff40: ffffc9000024ff50 (0xffffc9000024ff50)
  ffffc9000024ff48: 0000000000000018 (0x18)
  ffffc9000024ff50: ffffffff816b2e6a (entry_SYSCALL_64_fastpath+0x18/0xa8)
  ...

It unwinded from an interrupt which came in right after entry code
called into a C syscall handler, before it had a chance to set up the
frame pointer, so regs->bp still had its user space value.

Add a check to silence warnings in such a case, where an interrupt
has occurred and regs->sp is almost at the end of the stack.

Reported-by: Borislav Petkov <bp@suse.de>
Tested-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
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: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Fixes: c32c47c68a ("x86/unwind: Warn on bad frame pointer")
Link: http://lkml.kernel.org/r/c695f0d0d4c2cfe6542b90e2d0520e11eb901eb5.1493171120.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Josh Poimboeuf 2017-04-25 20:48:51 -05:00 committed by Ingo Molnar
parent dc912c3035
commit b0d50c7b5d
1 changed files with 17 additions and 3 deletions
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20
arch/x86/kernel/unwind_frame.c
View File

@ -91,16 +91,26 @@ static bool in_entry_code(unsigned long ip)
return false; return false;
} }
static inline unsigned long *last_frame(struct unwind_state *state)
{
return (unsigned long *)task_pt_regs(state->task) - 2;
}
#ifdef CONFIG_X86_32 #ifdef CONFIG_X86_32
#define GCC_REALIGN_WORDS 3 #define GCC_REALIGN_WORDS 3
#else #else
#define GCC_REALIGN_WORDS 1 #define GCC_REALIGN_WORDS 1
#endif #endif
static inline unsigned long *last_aligned_frame(struct unwind_state *state)
{
return last_frame(state) - GCC_REALIGN_WORDS;
}
static bool is_last_task_frame(struct unwind_state *state) static bool is_last_task_frame(struct unwind_state *state)
{ {
unsigned long *last_bp = (unsigned long *)task_pt_regs(state->task) - 2; unsigned long *last_bp = last_frame(state);
unsigned long *aligned_bp = last_bp - GCC_REALIGN_WORDS; unsigned long *aligned_bp = last_aligned_frame(state);
/* /*
* We have to check for the last task frame at two different locations * We have to check for the last task frame at two different locations
@ -277,10 +287,14 @@ bool unwind_next_frame(struct unwind_state *state)
/* /*
* Don't warn if the unwinder got lost due to an interrupt in entry * Don't warn if the unwinder got lost due to an interrupt in entry
* code before the stack was set up: * code or in the C handler before the first frame pointer got set up:
*/ */
if (state->got_irq && in_entry_code(state->ip)) if (state->got_irq && in_entry_code(state->ip))
goto the_end; goto the_end;
if (state->regs &&
state->regs->sp >= (unsigned long)last_aligned_frame(state) &&
state->regs->sp < (unsigned long)task_pt_regs(state->task))
goto the_end;
if (state->regs) { if (state->regs) {
printk_deferred_once(KERN_WARNING printk_deferred_once(KERN_WARNING