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tracing: Fix use-after-free in print_graph_function_flags during tracer switching

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commit 7f81f27b1093e4895e87b74143c59c055c3b1906 upstream.

Kairui reported a UAF issue in print_graph_function_flags() during
ftrace stress testing [1]. This issue can be reproduced if puting a
'mdelay(10)' after 'mutex_unlock(&trace_types_lock)' in s_start(),
and executing the following script:

  $ echo function_graph > current_tracer
  $ cat trace > /dev/null &
  $ sleep 5  # Ensure the 'cat' reaches the 'mdelay(10)' point
  $ echo timerlat > current_tracer

The root cause lies in the two calls to print_graph_function_flags
within print_trace_line during each s_show():

  * One through 'iter->trace->print_line()';
  * Another through 'event->funcs->trace()', which is hidden in
    print_trace_fmt() before print_trace_line returns.

Tracer switching only updates the former, while the latter continues
to use the print_line function of the old tracer, which in the script
above is print_graph_function_flags.

Moreover, when switching from the 'function_graph' tracer to the
'timerlat' tracer, s_start only calls graph_trace_close of the
'function_graph' tracer to free 'iter->private', but does not set
it to NULL. This provides an opportunity for 'event->funcs->trace()'
to use an invalid 'iter->private'.

To fix this issue, set 'iter->private' to NULL immediately after
freeing it in graph_trace_close(), ensuring that an invalid pointer
is not passed to other tracers. Additionally, clean up the unnecessary
'iter->private = NULL' during each 'cat trace' when using wakeup and
irqsoff tracers.

 [1] https://lore.kernel.org/all/20231112150030.84609-1-ryncsn@gmail.com/

Cc: stable@vger.kernel.org
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Zheng Yejian <zhengyejian1@huawei.com>
Link: https://lore.kernel.org/20250320122137.23635-1-wutengda@huaweicloud.com
Fixes: eecb91b9f98d ("tracing: Fix memleak due to race between current_tracer and trace")
Closes: https://lore.kernel.org/all/CAMgjq7BW79KDSCyp+tZHjShSzHsScSiJxn5ffskp-QzVM06fxw@mail.gmail.com/
Reported-by: Kairui Song <kasong@tencent.com>
Signed-off-by: Tengda Wu <wutengda@huaweicloud.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Tengda Wu 2025-03-20 12:21:37 +00:00 committed by Greg Kroah-Hartman
parent 3ac65de111
commit a2cce54c17
3 changed files with 1 additions and 4 deletions
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1
kernel/trace/trace_functions_graph.c
View File

@ -1244,6 +1244,7 @@ void graph_trace_close(struct trace_iterator *iter)
if (data) {
free_percpu(data->cpu_data);
kfree(data);
iter->private = NULL;
}
}

2
kernel/trace/trace_irqsoff.c
View File

@ -231,8 +231,6 @@ static void irqsoff_trace_open(struct trace_iterator *iter)
{
if (is_graph(iter->tr))
graph_trace_open(iter);
else
iter->private = NULL;
}
static void irqsoff_trace_close(struct trace_iterator *iter)

2
kernel/trace/trace_sched_wakeup.c
View File

@ -168,8 +168,6 @@ static void wakeup_trace_open(struct trace_iterator *iter)
{
if (is_graph(iter->tr))
graph_trace_open(iter);
else
iter->private = NULL;
}
static void wakeup_trace_close(struct trace_iterator *iter)