linux-kernel - [for-linus][PATCH 4/4] eventfs: Test for dentries array allocated in eventfs

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Date:   Sat, 30 Sep 2023 16:32:17 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     linux-kernel@...r.kernel.org
Cc:     Masami Hiramatsu <mhiramat@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: [for-linus][PATCH 4/4] eventfs: Test for dentries array allocated in eventfs_release()

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

The dcache_dir_open_wrapper() could be called when a dynamic event is
being deleted leaving a dentry with no children. In this case the
dlist->dentries array will never be allocated. This needs to be checked
for in eventfs_release(), otherwise it will trigger a NULL pointer
dereference.

Link: https://lore.kernel.org/linux-trace-kernel/20230930090106.1c3164e9@rorschach.local.home

Cc: Mark Rutland <mark.rutland@....com>
Acked-by: Masami Hiramatsu (Google) <mhiramat@...nel.org>
Fixes: ef36b4f92868 ("eventfs: Remember what dentries were created on dir open")
Signed-off-by: Steven Rostedt (Google) <rostedt@...dmis.org>
---
 fs/tracefs/event_inode.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/tracefs/event_inode.c b/fs/tracefs/event_inode.c
index 5f1714089884..8c8d64e76103 100644
--- a/fs/tracefs/event_inode.c
+++ b/fs/tracefs/event_inode.c
@@ -421,7 +421,7 @@ static int eventfs_release(struct inode *inode, struct file *file)
 	if (WARN_ON_ONCE(!dlist))
 		return -EINVAL;
 
-	for (i = 0; dlist->dentries[i]; i++) {
+	for (i = 0; dlist->dentries && dlist->dentries[i]; i++) {
 		dput(dlist->dentries[i]);
 	}
 
-- 
2.40.1