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* [PATCH] x86/stacktrace: Fix infinite loop in arch_stack_walk_user()
@ 2019-07-11  2:35 Eiichi Tsukata
  2019-07-11  4:10 ` Linus Torvalds
  2019-07-11  6:25 ` [tip:x86/urgent] x86/stacktrace: Prevent " tip-bot for Eiichi Tsukata
  0 siblings, 2 replies; 3+ messages in thread
From: Eiichi Tsukata @ 2019-07-11  2:35 UTC (permalink / raw)
  To: tglx, peterz, torvalds, rostedt, jpoimboe, mingo, bp, hpa, x86,
	linux-kernel
  Cc: Eiichi Tsukata

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

Once we find a lack of return address, there is no need to continue
loop, so let's break out.

Fixes: 02b67518e2b1 ("tracing: add support for userspace stacktraces in tracing/iter_ctrl")
Signed-off-by: Eiichi Tsukata <devel@etsukata.com>
---
 arch/x86/kernel/stacktrace.c | 7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/arch/x86/kernel/stacktrace.c b/arch/x86/kernel/stacktrace.c
index 2abf27d7df6b..b1a1f4b4c943 100644
--- a/arch/x86/kernel/stacktrace.c
+++ b/arch/x86/kernel/stacktrace.c
@@ -129,11 +129,8 @@ void arch_stack_walk_user(stack_trace_consume_fn consume_entry, void *cookie,
 			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 ||
+		    !consume_entry(cookie, frame.ret_addr, false))
 			break;
 		fp = frame.next_fp;
 	}
-- 
2.21.0


^ permalink raw reply related	[flat|nested] 3+ messages in thread
* Re: [PATCH] x86/stacktrace: Fix infinite loop in arch_stack_walk_user()
  2019-07-11  2:35 [PATCH] x86/stacktrace: Fix infinite loop in arch_stack_walk_user() Eiichi Tsukata
@ 2019-07-11  4:10 ` Linus Torvalds
  2019-07-11  6:25 ` [tip:x86/urgent] x86/stacktrace: Prevent " tip-bot for Eiichi Tsukata
  1 sibling, 0 replies; 3+ messages in thread
From: Linus Torvalds @ 2019-07-11  4:10 UTC (permalink / raw)
  To: Eiichi Tsukata
  Cc: Thomas Gleixner, Peter Zijlstra, Steven Rostedt, Josh Poimboeuf,
	Ingo Molnar, Borislav Petkov, Peter Anvin,
	the arch/x86 maintainers, Linux List Kernel Mailing

On Wed, Jul 10, 2019 at 7:35 PM Eiichi Tsukata <devel@etsukata.com> wrote:
>
> Once we find a lack of return address, there is no need to continue
> loop, so let's break out.

Looks good to me, feel free to add

  Acked-by: Linus Torvalds <torvalds@linux-foundation.org>

and I'll assume this comes through the x86 -tip tree..

         Linus

^ permalink raw reply	[flat|nested] 3+ messages in thread
* [tip:x86/urgent] x86/stacktrace: Prevent infinite loop in arch_stack_walk_user()
  2019-07-11  2:35 [PATCH] x86/stacktrace: Fix infinite loop in arch_stack_walk_user() Eiichi Tsukata
  2019-07-11  4:10 ` Linus Torvalds
@ 2019-07-11  6:25 ` tip-bot for Eiichi Tsukata
  1 sibling, 0 replies; 3+ messages in thread
From: tip-bot for Eiichi Tsukata @ 2019-07-11  6:25 UTC (permalink / raw)
  To: linux-tip-commits; +Cc: torvalds, devel, tglx, mingo, linux-kernel, hpa

Commit-ID:  cbf5b73d162b22e044fe0b7d51dcaa33be065253
Gitweb:     https://git.kernel.org/tip/cbf5b73d162b22e044fe0b7d51dcaa33be065253
Author:     Eiichi Tsukata <devel@etsukata.com>
AuthorDate: Thu, 11 Jul 2019 11:35:01 +0900
Committer:  Thomas Gleixner <tglx@linutronix.de>
CommitDate: Thu, 11 Jul 2019 08:22:03 +0200

x86/stacktrace: Prevent infinite loop in arch_stack_walk_user()

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@etsukata.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Link: https://lkml.kernel.org/r/20190711023501.963-1-devel@etsukata.com

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

diff --git a/arch/x86/kernel/stacktrace.c b/arch/x86/kernel/stacktrace.c
index 2abf27d7df6b..4f36d3241faf 100644
--- a/arch/x86/kernel/stacktrace.c
+++ b/arch/x86/kernel/stacktrace.c
@@ -129,11 +129,9 @@ void arch_stack_walk_user(stack_trace_consume_fn consume_entry, void *cookie,
 			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;
 	}

^ permalink raw reply related	[flat|nested] 3+ messages in thread
end of thread, other threads:[~2019-07-11  6:25 UTC | newest]

Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
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2019-07-11  2:35 [PATCH] x86/stacktrace: Fix infinite loop in arch_stack_walk_user() Eiichi Tsukata
2019-07-11  4:10 ` Linus Torvalds
2019-07-11  6:25 ` [tip:x86/urgent] x86/stacktrace: Prevent " tip-bot for Eiichi Tsukata

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