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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 <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;
}
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