linux-kernel - [tip:x86/asm] x86/dumpstack: Warn on stack recursion

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Message-ID: <tip-0d2b8579add41e08aa1110da864f1071d58e6048@git.kernel.org>
Date:   Thu, 27 Oct 2016 00:38:11 -0700
From:   tip-bot for Josh Poimboeuf <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     torvalds@...ux-foundation.org, bp@...en8.de, tglx@...utronix.de,
        mingo@...nel.org, luto@...nel.org, peterz@...radead.org,
        jpoimboe@...hat.com, linux-kernel@...r.kernel.org,
        brgerst@...il.com, dvlasenk@...hat.com, hpa@...or.com
Subject: [tip:x86/asm] x86/dumpstack: Warn on stack recursion

Commit-ID:  0d2b8579add41e08aa1110da864f1071d58e6048
Gitweb:     http://git.kernel.org/tip/0d2b8579add41e08aa1110da864f1071d58e6048
Author:     Josh Poimboeuf <jpoimboe@...hat.com>
AuthorDate: Wed, 26 Oct 2016 10:41:50 -0500
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Thu, 27 Oct 2016 08:32:38 +0200

x86/dumpstack: Warn on stack recursion

Print a warning if stack recursion is detected.

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/def18247aafaab480844484398e793f552b79bda.1477496147.git.jpoimboe@redhat.com
[ Unbroke the lines. ]
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 arch/x86/kernel/dumpstack_32.c | 4 +++-
 arch/x86/kernel/dumpstack_64.c | 4 +++-
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/dumpstack_32.c b/arch/x86/kernel/dumpstack_32.c
index 90cf460..d7d20999 100644
--- a/arch/x86/kernel/dumpstack_32.c
+++ b/arch/x86/kernel/dumpstack_32.c
@@ -109,8 +109,10 @@ recursion_check:
 	 * just break out and report an unknown stack type.
 	 */
 	if (visit_mask) {
-		if (*visit_mask & (1UL << info->type))
+		if (*visit_mask & (1UL << info->type)) {
+			printk_deferred_once(KERN_WARNING "WARNING: stack recursion on stack type %d\n", info->type);
 			goto unknown;
+		}
 		*visit_mask |= 1UL << info->type;
 	}
 
diff --git a/arch/x86/kernel/dumpstack_64.c b/arch/x86/kernel/dumpstack_64.c
index 310abf4..ab0f8b9 100644
--- a/arch/x86/kernel/dumpstack_64.c
+++ b/arch/x86/kernel/dumpstack_64.c
@@ -128,8 +128,10 @@ recursion_check:
 	 * just break out and report an unknown stack type.
 	 */
 	if (visit_mask) {
-		if (*visit_mask & (1UL << info->type))
+		if (*visit_mask & (1UL << info->type)) {
+			printk_deferred_once(KERN_WARNING "WARNING: stack recursion on stack type %d\n", info->type);
 			goto unknown;
+		}
 		*visit_mask |= 1UL << info->type;
 	}