From f4a771cc684c7354b6200147f7252c58d17408ff Mon Sep 17 00:00:00 2001 From: Steven Rostedt Date: Fri, 28 Aug 2026 09:41:53 -0400 Subject: [PATCH] tracing: Have show_event_filters/triggers files take trace array ref The newly added files show_event_filters and show_event_triggers that show all filters or triggers that are set within the trace array do not take a reference for the trace array it is showing. Without taking a reference, the trace_array may be freed via "rmdir" while a task is reading one of theses files. Those files iterate all the events within an instance (trace_array) and nothing prevents that instance from being freed while its data is being read. This causes a use-after-free crash. Have the open of both those files take the trace_array reference via the trace_array_get() that prevents the trace_array from being freed while the files are opened. Cc: stable@vger.kernel.org Link: https://patch.msgid.link/20260828094153.17b95037@gandalf.local.home Fixes: 729757b96a662 ("tracing: Add show_event_filters to expose active event filters") Fixes: 6a80838814eea ("tracing: Add show_event_triggers to expose active event triggers") Reported-by: Farhad Alemi Closes: https://lore.kernel.org/all/CA+0ovCjerKZJLwXScM9bF2ga2rLi4_XOpUfK41NDbENpeu98jA@mail.gmail.com/ Reviewed-by: Aaron Tomlin Signed-off-by: Steven Rostedt --- kernel/trace/trace_events.c | 28 ++++++++++++++++++++++++---- 1 file changed, 24 insertions(+), 4 deletions(-) diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c index 1d39eaf6a0f7..9dbc2441763b 100644 --- a/kernel/trace/trace_events.c +++ b/kernel/trace/trace_events.c @@ -2736,14 +2736,14 @@ static const struct file_operations ftrace_show_event_filters_fops = { .open = ftrace_event_show_filters_open, .read = seq_read, .llseek = seq_lseek, - .release = seq_release, + .release = ftrace_event_release, }; static const struct file_operations ftrace_show_event_triggers_fops = { .open = ftrace_event_show_triggers_open, .read = seq_read, .llseek = seq_lseek, - .release = seq_release, + .release = ftrace_event_release, }; static const struct file_operations ftrace_set_event_pid_fops = { @@ -2908,7 +2908,17 @@ ftrace_event_set_open(struct inode *inode, struct file *file) static int ftrace_event_show_filters_open(struct inode *inode, struct file *file) { - return ftrace_event_open(inode, file, &show_show_event_filters_seq_ops); + struct trace_array *tr = inode->i_private; + int ret; + + ret = tracing_check_open_get_tr(tr); + if (ret) + return ret; + + ret = ftrace_event_open(inode, file, &show_show_event_filters_seq_ops); + if (ret < 0) + trace_array_put(tr); + return ret; } /** @@ -2922,7 +2932,17 @@ ftrace_event_show_filters_open(struct inode *inode, struct file *file) static int ftrace_event_show_triggers_open(struct inode *inode, struct file *file) { - return ftrace_event_open(inode, file, &show_show_event_triggers_seq_ops); + struct trace_array *tr = inode->i_private; + int ret; + + ret = tracing_check_open_get_tr(tr); + if (ret) + return ret; + + ret = ftrace_event_open(inode, file, &show_show_event_triggers_seq_ops); + if (ret < 0) + trace_array_put(tr); + return ret; } static int