[PATCH 2/5] tracing: Fix checking of freed trace_event_file for id files
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STALE240d
From: Petr Pavlu <petr.pavlu@suse.com>
Date: 2026-02-10 11:34:51
Also in:
lkml
Subsystem:
the rest, tracing · Maintainers:
Linus Torvalds, Steven Rostedt, Masami Hiramatsu
Revision v1 of 3 in this series.
Revisions (3)
- v1 current
- v2 [diff vs current]
- v3 [diff vs current]
The code for reading an event id currently uses file->f_inode->i_private to
store the value of trace_event_file->event_call->event.type, unlike all
other event files which use it to store a pointer to the associated
trace_event_file data. The event_id_read() function retrieves this id value
from i_private and checks if it is non-0/NULL to determine whether the
event is still valid. This approach worked in the past when
remove_event_file_dir() would set i_private to NULL for all files in an
event directory upon removal. However, with the introduction of eventfs,
i_private is assigned when an eventfs inode is allocated and remains set
throughout its lifetime. As a result, event_id_read() may fail to detect
that an event is being removed.
Fix this issue by changing the event id file to use i_private to store
a trace_event_file pointer and utilize event_file_file() to check for the
EVENT_FILE_FL_FREED flag.
Fixes: 6fdac58c560e ("tracing: Remove unused trace_event_file dir field")
Signed-off-by: Petr Pavlu <petr.pavlu@suse.com>
---
kernel/trace/trace_events.c | 14 +++++++++++---
1 file changed, 11 insertions(+), 3 deletions(-)
diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index e8ed6ba155cf..3d272b3cd688 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c@@ -2090,11 +2090,18 @@ static int trace_format_open(struct inode *inode, struct file *file) static ssize_t event_id_read(struct file *filp, char __user *ubuf, size_t cnt, loff_t *ppos) { - int id = (long)event_file_data(filp); + struct trace_event_file *file; + int id; char buf[32]; int len; - if (unlikely(!id)) + mutex_lock(&event_mutex); + file = event_file_file(filp); + if (likely(file)) + id = file->event_call->event.type; + mutex_unlock(&event_mutex); + + if (!file) return -ENODEV; len = sprintf(buf, "%d\n", id);
@@ -2572,7 +2579,9 @@ static const struct file_operations ftrace_event_format_fops = { #ifdef CONFIG_PERF_EVENTS static const struct file_operations ftrace_event_id_fops = { + .open = tracing_open_file_tr, .read = event_id_read, + .release = tracing_release_file_tr, .llseek = default_llseek, }; #endif
@@ -2936,7 +2945,6 @@ static int event_callback(const char *name, umode_t *mode, void **data, if (call->event.type && call->class->reg && strcmp(name, "id") == 0) { *mode = TRACE_MODE_READ; - *data = (void *)(long)call->event.type; *fops = &ftrace_event_id_fops; return 1; }
--
2.52.0