[PATCH v2 43/44] x86/unwind: warn on bad stack return address

From: Josh Poimboeuf
Date: Thu Aug 04 2016 - 18:24:44 EST


If __kernel_text_address() doesn't recognize a return address on the
stack, it probably means that it's some generated code which
__kernel_text_address() doesn't know about yet.

Otherwise there's probably some stack corruption.

Either way, warn about it.

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@xxxxxxxxxx>
---
arch/x86/kernel/unwind_frame.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/unwind_frame.c b/arch/x86/kernel/unwind_frame.c
index d90c2c9..f943413 100644
--- a/arch/x86/kernel/unwind_frame.c
+++ b/arch/x86/kernel/unwind_frame.c
@@ -17,7 +17,13 @@ unsigned long unwind_get_return_address(struct unwind_state *state)
addr = ftrace_graph_ret_addr(state->task, &state->graph_idx, *addr_p,
addr_p);

- return __kernel_text_address(addr) ? addr : 0;
+ if (!__kernel_text_address(addr)) {
+ printk_deferred_once(KERN_WARNING "WARNING: unrecognized kernel stack return address %p in %s:%d\n",
+ (void *)addr, state->task->comm, state->task->pid);
+ return 0;
+ }
+
+ return addr;
}
EXPORT_SYMBOL_GPL(unwind_get_return_address);

--
2.7.4