[34/90] cifs: cope with negative dentries in cifs_get_root

[Greg KH]

3.0-stable review patch.  If anyone has any objections, please let us know.

------------------

From: Jeff Layton <jlayton@xxxxxxxxxx>

commit 80975d21aae2136ccae1ce914a1602dc1d8b0795 upstream.

The loop around lookup_one_len doesn't handle the case where it might
return a negative dentry, which can cause an oops on the next pass
through the loop. Check for that and break out of the loop with an
error of -ENOENT if there is one.

Fixes the panic reported here:

    https://bugzilla.redhat.com/show_bug.cgi?id=727927

Reported-by: TR Bentley <home@xxxxxxxxxxxxxxx>
Reported-by: Iain Arnell <iarnell@xxxxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx>
Signed-off-by: Steve French <sfrench@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>

---
 fs/cifs/cifsfs.c |    4 ++++
 1 file changed, 4 insertions(+)

--- a/fs/cifs/cifsfs.c
+++ b/fs/cifs/cifsfs.c
@@ -581,6 +581,10 @@ cifs_get_root(struct smb_vol *vol, struc
 		mutex_unlock(&dir->i_mutex);
 		dput(dentry);
 		dentry = child;
+		if (!dentry->d_inode) {
+			dput(dentry);
+			dentry = ERR_PTR(-ENOENT);
+		}
 	} while (!IS_ERR(dentry));
 	_FreeXid(xid);
 	kfree(full_path);


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