Commit c32c47c6 authored Oct 26, 2016 by Josh Poimboeuf Committed by Ingo Molnar Oct 27, 2016

x86/unwind: Warn on bad frame pointer



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 <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>
Link: http://lkml.kernel.org/r/03c888f6f7414d54fa56b393ea25482be6899b5f.1477496147.git.jpoimboe@redhat.com


Signed-off-by: Ingo Molnar <mingo@kernel.org>

parent bb12d674

arch/x86/kernel/unwind_frame.c

+16 −2

Original line number	Diff line number	Diff line
		@@ -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;