From 9c2d2056647790c5034d722bd24e9d913ebca73c Mon Sep 17 00:00:00 2001 From: Tyler Hicks Date: Tue, 22 Sep 2009 12:52:17 -0500 Subject: [PATCH] eCryptfs: Prevent lower dentry from going negative during unlink MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit When calling vfs_unlink() on the lower dentry, d_delete() turns the dentry into a negative dentry when the d_count is 1. This eventually caused a NULL pointer deref when a read() or write() was done and the negative dentry's d_inode was dereferenced in ecryptfs_read_update_atime() or ecryptfs_getxattr(). Placing mutt's tmpdir in an eCryptfs mount is what initially triggered the oops and I was able to reproduce it with the following sequence: open("/tmp/upper/foo", O_RDWR|O_CREAT|O_EXCL|O_NOFOLLOW, 0600) = 3 link("/tmp/upper/foo", "/tmp/upper/bar") = 0 unlink("/tmp/upper/foo") = 0 open("/tmp/upper/bar", O_RDWR|O_CREAT|O_NOFOLLOW, 0600) = 4 unlink("/tmp/upper/bar") = 0 write(4, "eCryptfs test\n"..., 14 +++ killed by SIGKILL +++ https://bugs.launchpad.net/ecryptfs/+bug/387073 Reported-by: Loïc Minier Cc: Serge Hallyn Cc: Dave Kleikamp Cc: ecryptfs-devel@lists.launchpad.net Cc: stable Signed-off-by: Tyler Hicks --- fs/ecryptfs/inode.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/fs/ecryptfs/inode.c b/fs/ecryptfs/inode.c index 2f0945d6329..056fed62d0d 100644 --- a/fs/ecryptfs/inode.c +++ b/fs/ecryptfs/inode.c @@ -476,6 +476,7 @@ static int ecryptfs_unlink(struct inode *dir, struct dentry *dentry) struct inode *lower_dir_inode = ecryptfs_inode_to_lower(dir); struct dentry *lower_dir_dentry; + dget(lower_dentry); lower_dir_dentry = lock_parent(lower_dentry); rc = vfs_unlink(lower_dir_inode, lower_dentry); if (rc) { @@ -489,6 +490,7 @@ static int ecryptfs_unlink(struct inode *dir, struct dentry *dentry) d_drop(dentry); out_unlock: unlock_dir(lower_dir_dentry); + dput(lower_dentry); return rc; }