linux-kernel - [PATCH 5.2 357/413] x86/stacktrace: Prevent infinite loop in arch_stack_walk

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Date:   Wed, 24 Jul 2019 21:20:48 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Eiichi Tsukata <devel@...ukata.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: [PATCH 5.2 357/413] x86/stacktrace: Prevent infinite loop in arch_stack_walk_user()

From: Eiichi Tsukata <devel@...ukata.com>

commit cbf5b73d162b22e044fe0b7d51dcaa33be065253 upstream.

arch_stack_walk_user() checks `if (fp == frame.next_fp)` to prevent a
infinite loop by self reference but it's not enogh for circular reference.

Once a lack of return address is found, there is no point to continue the
loop, so break out.

Fixes: 02b67518e2b1 ("tracing: add support for userspace stacktraces in tracing/iter_ctrl")
Signed-off-by: Eiichi Tsukata <devel@...ukata.com>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Acked-by: Linus Torvalds <torvalds@...ux-foundation.org>
Link: https://lkml.kernel.org/r/20190711023501.963-1-devel@etsukata.com
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/x86/kernel/stacktrace.c |    8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

--- a/arch/x86/kernel/stacktrace.c
+++ b/arch/x86/kernel/stacktrace.c
@@ -129,11 +129,9 @@ void arch_stack_walk_user(stack_trace_co
 			break;
 		if ((unsigned long)fp < regs->sp)
 			break;
-		if (frame.ret_addr) {
-			if (!consume_entry(cookie, frame.ret_addr, false))
-				return;
-		}
-		if (fp == frame.next_fp)
+		if (!frame.ret_addr)
+			break;
+		if (!consume_entry(cookie, frame.ret_addr, false))
 			break;
 		fp = frame.next_fp;
 	}