Commit ba376f96 authored Sep 30, 2024 by Steven Rostedt Committed by Zheng Yejian Sep 30, 2024

tracing/timerlat: Only clear timer if a kthread exists

stable inclusion
from stable-v6.6.51
commit 8c72f0b2c45f21cb8b00fc37f79f632d7e46c2ed
category: bugfix
bugzilla: https://gitee.com/src-openeuler/kernel/issues/IAU9OQ
CVE: CVE-2024-46845

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=8c72f0b2c45f21cb8b00fc37f79f632d7e46c2ed

--------------------------------

commit e6a53481da292d970d1edf0d8831121d1c5e2f0d upstream.

The timerlat tracer can use user space threads to check for osnoise and
timer latency. If the program using this is killed via a SIGTERM, the
threads are shutdown one at a time and another tracing instance can start
up resetting the threads before they are fully closed. That causes the
hrtimer assigned to the kthread to be shutdown and freed twice when the
dying thread finally closes the file descriptors, causing a use-after-free
bug.

Only cancel the hrtimer if the associated thread is still around. Also add
the interface_lock around the resetting of the tlat_var->kthread.

Note, this is just a quick fix that can be backported to stable. A real
fix is to have a better synchronization between the shutdown of old
threads and the starting of new ones.

Link: https://lore.kernel.org/all/20240820130001.124768-1-tglozar@redhat.com/

Cc: stable@vger.kernel.org
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: "Luis Claudio R. Goncalves" <lgoncalv@redhat.com>
Link: https://lore.kernel.org/20240905085330.45985730@gandalf.local.home


Fixes: e88ed227 ("tracing/timerlat: Add user-space interface")
Reported-by: Tomas Glozar <tglozar@redhat.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Zheng Yejian <zhengyejian1@huawei.com>

parent 02590a1a

kernel/trace/trace_osnoise.c

+13 −6

Original line number	Diff line number	Diff line
		@@ -252,6 +252,11 @@ static inline struct timerlat_variables *this_cpu_tmr_var(void)
		return this_cpu_ptr(&per_cpu_timerlat_var);
		}

		/*
		* Protect the interface.
		*/
		static struct mutex interface_lock;

		/*
		* tlat_var_reset - Reset the values of the given timerlat_variables
		*/
		@@ -259,14 +264,20 @@ static inline void tlat_var_reset(void)
		{
		struct timerlat_variables *tlat_var;
		int cpu;

		/* Synchronize with the timerlat interfaces */
		mutex_lock(&interface_lock);
		/*
		* So far, all the values are initialized as 0, so
		* zeroing the structure is perfect.
		*/
		for_each_cpu(cpu, cpu_online_mask) {
		tlat_var = per_cpu_ptr(&per_cpu_timerlat_var, cpu);
		if (tlat_var->kthread)
		hrtimer_cancel(&tlat_var->timer);
		memset(tlat_var, 0, sizeof(*tlat_var));
		}
		mutex_unlock(&interface_lock);
		}
		#else /* CONFIG_TIMERLAT_TRACER */
		#define tlat_var_reset() do {} while (0)
		@@ -331,11 +342,6 @@ struct timerlat_sample {
		};
		#endif

		/*
		* Protect the interface.
		*/
		static struct mutex interface_lock;

		/*
		* Tracer data.
		*/
		@@ -2591,6 +2597,7 @@ static int timerlat_fd_release(struct inode inode, struct file file)
		osn_var = per_cpu_ptr(&per_cpu_osnoise_var, cpu);
		tlat_var = per_cpu_ptr(&per_cpu_timerlat_var, cpu);

		if (tlat_var->kthread)
		hrtimer_cancel(&tlat_var->timer);
		memset(tlat_var, 0, sizeof(*tlat_var));