2019-07-11 02:37:16

by Eiichi Tsukata

Subject: [PATCH] x86/stacktrace: Fix infinite loop in arch_stack_walk_user()

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 <[email protected]>
---
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

2019-07-11 04:20:31

by Linus Torvalds

Subject: Re: [PATCH] x86/stacktrace: Fix infinite loop in arch_stack_walk_user()

On Wed, Jul 10, 2019 at 7:35 PM Eiichi Tsukata <[email protected]> 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 <[email protected]>

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

Linus

2019-07-11 06:28:23

by tip-bot for Vasyl Gomonovych

Subject: [tip:x86/urgent] x86/stacktrace: Prevent infinite loop in arch_stack_walk_user()

Commit-ID: cbf5b73d162b22e044fe0b7d51dcaa33be065253
Gitweb: https://git.kernel.org/tip/cbf5b73d162b22e044fe0b7d51dcaa33be065253
Author: Eiichi Tsukata <[email protected]>
AuthorDate: Thu, 11 Jul 2019 11:35:01 +0900
Committer: Thomas Gleixner <[email protected]>
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 <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Acked-by: Linus Torvalds <[email protected]>
Link: https://lkml.kernel.org/r/[email protected]

---
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;
}