diff mbox

[4.2.y-ckt,025/268] ovl: check dentry positiveness in ovl_cleanup_whiteouts()

Message ID 1453926929-17663-26-git-send-email-kamal@canonical.com
State New
Headers show

Commit Message

Kamal Mostafa Jan. 27, 2016, 8:31 p.m. UTC 
4.2.8-ckt3 -stable review patch.  If anyone has any objections, please let me know.

---8<------------------------------------------------------------

From: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>

commit 84889d49335627bc770b32787c1ef9ebad1da232 upstream.

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 <khlebnikov@yandex-team.ru>
Signed-off-by: Miklos Szeredi <miklos@szeredi.hu>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
---
 fs/overlayfs/readdir.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)
diff mbox

Patch

diff --git a/fs/overlayfs/readdir.c b/fs/overlayfs/readdir.c
index 70e9af5..adcb139 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);