Detect situations in the unwinder where the frame pointer refers to a
bad address, and print an appropriate warning.
Use printk_deferred_once() because the unwinder can be called with the
console lock by lockdep via save_stack_trace().
Signed-off-by: Josh Poimboeuf <jpoim...@redhat.com>
---
arch/x86/kernel/unwind_frame.c | 18 ++++++++++++++++--
1 file changed, 16 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kernel/unwind_frame.c b/arch/x86/kernel/unwind_frame.c
index 5795427..9be9a8f 100644
--- a/arch/x86/kernel/unwind_frame.c
+++ b/arch/x86/kernel/unwind_frame.c
@@ -123,8 +123,17 @@ bool unwind_next_frame(struct unwind_state *state)
}
/* make sure the next frame's data is accessible */
- if (!update_stack_state(state, next_frame, next_len))
- return false;
+ if (!update_stack_state(state, next_frame, next_len)) {
+ /*
+ * Don't warn on bad regs->bp. An interrupt in entry code
+ * might cause a false positive warning.
+ */
+ if (state->regs)
+ goto the_end;
+
+ goto bad_address;
+ }
+
/* move to the next frame */
if (regs) {
state->regs = regs;
@@ -136,6 +145,11 @@ bool unwind_next_frame(struct unwind_state *state)
return true;
+bad_address:
+ printk_deferred_once(KERN_WARNING
+ "WARNING: kernel stack frame pointer at %p in %s:%d has bad
value %p\n",
+ state->bp, state->task->comm,
+ state->task->pid, next_bp);
the_end:
state->stack_info.type = STACK_TYPE_UNKNOWN;
return false;
--
2.7.4
