Add a sanity check to ensure the stack only grows down, and print a warning if the check fails.
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 <[email protected]> --- arch/x86/kernel/unwind_frame.c | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/arch/x86/kernel/unwind_frame.c b/arch/x86/kernel/unwind_frame.c index f943413..a29c342 100644 --- a/arch/x86/kernel/unwind_frame.c +++ b/arch/x86/kernel/unwind_frame.c @@ -107,6 +107,7 @@ bool unwind_next_frame(struct unwind_state *state) { struct pt_regs *regs; unsigned long *next_bp; + enum stack_type prev_type = state->stack_info.type; state->regs = NULL; @@ -186,6 +187,15 @@ bool unwind_next_frame(struct unwind_state *state) return false; } + /* make sure the stack only unwinds up */ + if (state->stack_info.type == prev_type && next_bp <= state->bp) { + printk_deferred_once(KERN_WARNING "WARNING: kernel stack frame pointer at %p in %s:%d points the wrong way (%p)\n", + state->bp, state->task->comm, + state->task->pid, next_bp); + state->stack_info.type = STACK_TYPE_UNKNOWN; + return false; + } + /* move to the next frame */ state->bp = next_bp; return true; -- 2.7.4
