From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Subject: [PATCH] ovl: check dentry positiveness in ovl_cleanup_whiteouts() From: Konstantin Khlebnikov To: David Howells , Miklos Szeredi Cc: Al Viro , linux-kernel@vger.kernel.org, stable@vger.kernel.org, linux-unionfs@vger.kernel.org Date: Mon, 16 Nov 2015 18:44:11 +0300 Message-ID: <20151116154411.6862.28435.stgit@buzz> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: This patch fixes kernel crash at removing directory which contains whiteouts from lower layers. Cache of directory content passed as "list" contains entries from all layers, including whiteouts from lower layers. So, lookup in upper dir (moved into work at this stage) will return negative entry. Plus this cache is filled long before and we can race with external removal. Example: mkdir -p lower0/dir lower1/dir upper work overlay touch lower0/dir/a lower0/dir/b mknod lower1/dir/a c 0 0 mount -t overlay none overlay -o lowerdir=lower1:lower0,upperdir=upper,workdir=work rm -fr overlay/dir Signed-off-by: Konstantin Khlebnikov Cc: Stable # 3.18+ --- fs/overlayfs/readdir.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/fs/overlayfs/readdir.c b/fs/overlayfs/readdir.c index 70e9af551600..adcb1398c481 100644 --- a/fs/overlayfs/readdir.c +++ b/fs/overlayfs/readdir.c @@ -571,7 +571,8 @@ void ovl_cleanup_whiteouts(struct dentry *upper, struct list_head *list) (int) PTR_ERR(dentry)); continue; } - ovl_cleanup(upper->d_inode, dentry); + if (dentry->d_inode) + ovl_cleanup(upper->d_inode, dentry); dput(dentry); } mutex_unlock(&upper->d_inode->i_mutex);