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samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-modify

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ftrace_direct_init() assigns kthread_run()'s return value to simple_tsk
without an IS_ERR() check. When kthread_run() fails it returns
ERR_PTR(-ENOMEM), but init still returns 0, so the module loads with
simple_tsk holding an error pointer. On unload, ftrace_direct_exit()
then passes that ERR_PTR to kthread_stop(), leading to a
null-pointer-dereference.

Check the return value of kthread_run() with IS_ERR(); on failure,
unregister the ftrace direct call and propagate the error code.

Link: https://patch.msgid.link/20260826015034.10755-1-vulab@iscas.ac.cn
Fixes: ae0cc3b7e7 ("ftrace/samples: Add a sample module that implements modify_ftrace_direct()")
Suggested-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Haotian Zhang <vulab@iscas.ac.cn>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
This commit is contained in:
Haotian Zhang 2026-08-26 09:50:34 +08:00 committed by Steven Rostedt
parent 1704aaaf5d
commit d79fb758e7
1 changed files with 9 additions and 3 deletions
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12
samples/ftrace/ftrace-direct-modify.c
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@ -320,9 +320,15 @@ static int __init ftrace_direct_init(void)
ftrace_set_filter_ip(&direct, (unsigned long) my_ip, 0, 0);
ret = register_ftrace_direct(&direct, my_tramp);
if (!ret)
simple_tsk = kthread_run(simple_thread, NULL, "event-sample-fn");
return ret;
if (ret)
return ret;
simple_tsk = kthread_run(simple_thread, NULL, "event-sample-fn");
if (IS_ERR(simple_tsk)) {
unregister_ftrace_direct(&direct, my_tramp, true);
return PTR_ERR(simple_tsk);
}
return 0;
}
static void __exit ftrace_direct_exit(void)