linux-kernel - [PATCH] namei: free new

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Date:   Sat, 24 Nov 2018 17:23:24 +0800
From:   Pan Bian <bianpan2016@....com>
To:     Alexander Viro <viro@...iv.linux.org.uk>
Cc:     linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        Pan Bian <bianpan2016@....com>
Subject: [PATCH] namei: free new_dentry late

After calling dput(new_dentry), new_dentry is passed to fsnotify_move.
This may result in a use-after-free bug. This patch moves the put
operation late.

Fixes: 49d31c2f389a("dentry name snapshots")
Signed-off-by: Pan Bian <bianpan2016@....com>
---
 fs/namei.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/namei.c b/fs/namei.c
index 0cab649..8b104d9 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -4498,7 +4498,6 @@ int vfs_rename(struct inode *old_dir, struct dentry *old_dentry,
 		unlock_two_nondirectories(source, target);
 	else if (target)
 		inode_unlock(target);
-	dput(new_dentry);
 	if (!error) {
 		fsnotify_move(old_dir, new_dir, old_name.name, is_dir,
 			      !(flags & RENAME_EXCHANGE) ? target : NULL, old_dentry);
@@ -4507,6 +4506,7 @@ int vfs_rename(struct inode *old_dir, struct dentry *old_dentry,
 				      new_is_dir, NULL, new_dentry);
 		}
 	}
+	dput(new_dentry);
 	release_dentry_name_snapshot(&old_name);
 
 	return error;
-- 
2.7.4