On Thu, Apr 20, 2017 at 08:30:21AM -0500, Josh Poimboeuf wrote:
> On Thu, Apr 20, 2017 at 01:06:10PM +0200, Borislav Petkov wrote:
> > Hi,
> >
> > the splat below started appearing on one of the boxes here with
> > rc7+tip/master from yesterday.
> >
> > Ideas?
>
> Thanks for reporting it. This is another false positive. It unwinded
> from an interrupt which came in right after calling into C code, but
> before it could set up the frame pointer. This needs another unwinder
> check.
If it's recreatable, can you test with the following patch?
diff --git a/arch/x86/kernel/unwind_frame.c b/arch/x86/kernel/unwind_frame.c
index bda82df..abe36ff 100644
--- a/arch/x86/kernel/unwind_frame.c
+++ b/arch/x86/kernel/unwind_frame.c
@@ -91,16 +91,26 @@ static bool in_entry_code(unsigned long ip)
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
#define GCC_REALIGN_WORDS 3
#else
#define GCC_REALIGN_WORDS 1
#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)
{
- unsigned long *last_bp = (unsigned long *)task_pt_regs(state->task) - 2;
- unsigned long *aligned_bp = last_bp - GCC_REALIGN_WORDS;
+ unsigned long *last_bp = last_frame(state);
+ unsigned long *aligned_bp = last_aligned_frame(state);
/*
* We have to check for the last task frame at two different locations
@@ -277,10 +287,12 @@ bool unwind_next_frame(struct unwind_state *state)
/*
* Don't warn if the unwinder got lost due to an interrupt in entry
- * code before the stack was set up:
+ * code before the first frame pointer got set up:
*/
if (state->got_irq && in_entry_code(state->ip))
goto the_end;
+ if (state->regs && (unsigned long *)state->regs->sp >=
last_aligned_frame(state))
+ goto the_end;
if (state->regs) {
printk_deferred_once(KERN_WARNING
