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Message-ID: <20231030104127.6f32c932@gandalf.local.home>
Date: Mon, 30 Oct 2023 10:41:27 -0400
From: Steven Rostedt <rostedt@...dmis.org>
To: Naresh Kamboju <naresh.kamboju@...aro.org>
Cc: LKML <linux-kernel@...r.kernel.org>,
Linux trace kernel <linux-trace-kernel@...r.kernel.org>,
Masami Hiramatsu <mhiramat@...nel.org>,
Mark Rutland <mark.rutland@....com>,
Arnd Bergmann <arnd@...db.de>,
"Naresh Kamboju <naresh.kamboju@...aro.org>, Beau Belgrave
<beaub@...ux.microsoft.com>, Ajay Kaher <akaher@...are.com>, Andrew
Morton" <akpm@...ux-foundation.org>, lkft-triage@...ts.linaro.org
Subject: Re: [PATCH v2] eventfs: Test for ei->is_freed when accessing
ei->dentry
On Mon, 30 Oct 2023 12:37:08 +0530
Naresh Kamboju <naresh.kamboju@...aro.org> wrote:
>
> I have tested the linux-trace.git trace/core and run selftests ftrace
> the reported kernel panic [1] & [2] has been fixed but found
Good to know. Can I add "Tested-by" from you for that bug fix?
> "general protection fault" at kernel/trace/trace_events.c:2439.
Can you test with the below patch?
Also, can I ask what are you testing this on that makes it trigger so
easily? As I'm not able to trigger these in my tests, even though they are
indeed bugs.
-- Steve
diff --git a/fs/tracefs/event_inode.c b/fs/tracefs/event_inode.c
index 7ad7496bd597..7a0b54ddda24 100644
--- a/fs/tracefs/event_inode.c
+++ b/fs/tracefs/event_inode.c
@@ -609,7 +609,13 @@ static struct dentry *eventfs_root_lookup(struct inode *dir,
entry = &ei->entries[i];
if (strcmp(name, entry->name) == 0) {
void *cdata = data;
- r = entry->callback(name, &mode, &cdata, &fops);
+ mutex_lock(&eventfs_mutex);
+ /* If ei->is_freed, then the event itself may be too */
+ if (!ei->is_freed)
+ r = entry->callback(name, &mode, &cdata, &fops);
+ else
+ r = -1;
+ mutex_unlock(&eventfs_mutex);
if (r <= 0)
continue;
ret = simple_lookup(dir, dentry, flags);
@@ -743,7 +749,13 @@ static int dcache_dir_open_wrapper(struct inode *inode, struct file *file)
void *cdata = data;
entry = &ei->entries[i];
name = entry->name;
- r = entry->callback(name, &mode, &cdata, &fops);
+ mutex_lock(&eventfs_mutex);
+ /* If ei->is_freed, then the event itself may be too */
+ if (!ei->is_freed)
+ r = entry->callback(name, &mode, &cdata, &fops);
+ else
+ r = -1;
+ mutex_unlock(&eventfs_mutex);
if (r <= 0)
continue;
d = create_file_dentry(ei, i, parent, name, mode, cdata, fops, false);
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