linux-kernel - [tip:x86/asm] x86/unwind: Detect bad stack return address

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Message-ID: <tip-b6959a362177053c1c90db6dc1af25b6bddd8548@git.kernel.org>
Date:   Thu, 27 Oct 2016 00:38:45 -0700
From:   tip-bot for Josh Poimboeuf <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     torvalds@...ux-foundation.org, luto@...nel.org, hpa@...or.com,
        brgerst@...il.com, linux-kernel@...r.kernel.org,
        peterz@...radead.org, bp@...en8.de, dvlasenk@...hat.com,
        tglx@...utronix.de, mingo@...nel.org, jpoimboe@...hat.com
Subject: [tip:x86/asm] x86/unwind: Detect bad stack return address

Commit-ID:  b6959a362177053c1c90db6dc1af25b6bddd8548
Gitweb:     http://git.kernel.org/tip/b6959a362177053c1c90db6dc1af25b6bddd8548
Author:     Josh Poimboeuf <jpoimboe@...hat.com>
AuthorDate: Wed, 26 Oct 2016 10:41:51 -0500
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Thu, 27 Oct 2016 08:32:38 +0200

x86/unwind: Detect bad stack return address

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@...hat.com>
Cc: Andy Lutomirski <luto@...nel.org>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Brian Gerst <brgerst@...il.com>
Cc: Denys Vlasenko <dvlasenk@...hat.com>
Cc: H. Peter Anvin <hpa@...or.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Link: http://lkml.kernel.org/r/2d897898f324e275943b590d160b55e482bba65f.1477496147.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 arch/x86/kernel/unwind_frame.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/unwind_frame.c b/arch/x86/kernel/unwind_frame.c
index 9be9a8f..5639db6 100644
--- a/arch/x86/kernel/unwind_frame.c
+++ b/arch/x86/kernel/unwind_frame.c
@@ -20,7 +20,15 @@ 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 at %p in %s:%d\n",
+			(void *)addr, addr_p, state->task->comm,
+			state->task->pid);
+		return 0;
+	}
+
+	return addr;
 }
 EXPORT_SYMBOL_GPL(unwind_get_return_address);