linux-kernel - [v6.6][PATCH] eventfs: Check for NULL ef in eventfs_set

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Date:   Sun, 12 Nov 2023 12:18:17 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     LKML <linux-kernel@...r.kernel.org>,
        stable <stable@...r.kernel.org>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Milian Wolff <milian.wolff@...b.com>, akaher@...are.com,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: [v6.6][PATCH] eventfs: Check for NULL ef in eventfs_set_attr()

From: "Steven Rostedt (Google)" <rostedt@...dmis.org>

The top level events directory dentry does not have a d_fsdata set to a
eventfs_file pointer. This dentry is still passed to eventfs_set_attr().
It can not assume that the d_fsdata is set. Check for that.

Link: https://lore.kernel.org/all/20231112104158.6638-1-milian.wolff@kdab.com/

Fixes: 9aaee3eebc91 ("eventfs: Save ownership and mode")
Reported-by: Milian Wolff <milian.wolff@...b.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@...dmis.org>
---

Note: This only affects 6.6 as the code in 6.7 here was rewritten.
   I tested 6.7 and it does not have this bug.

 fs/tracefs/event_inode.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/tracefs/event_inode.c b/fs/tracefs/event_inode.c
index 5fcfb634fec2..efbdc47c74dc 100644
--- a/fs/tracefs/event_inode.c
+++ b/fs/tracefs/event_inode.c
@@ -113,14 +113,14 @@ static int eventfs_set_attr(struct mnt_idmap *idmap, struct dentry *dentry,
 
 	mutex_lock(&eventfs_mutex);
 	ef = dentry->d_fsdata;
-	if (ef->is_freed) {
+	if (ef && ef->is_freed) {
 		/* Do not allow changes if the event is about to be removed. */
 		mutex_unlock(&eventfs_mutex);
 		return -ENODEV;
 	}
 
 	ret = simple_setattr(idmap, dentry, iattr);
-	if (!ret)
+	if (!ret && ef)
 		update_attr(ef, iattr);
 	mutex_unlock(&eventfs_mutex);
 	return ret;
-- 
2.42.0