cifs: fix kref underflow in close_shroot()

Fix a bug where we used to not initialize the cached fid structure at all
in open_shroot() if the open was successful but we did not get a lease.
This would leave the structure uninitialized and later when we close the handle
we would in close_shroot() try to kref_put() an uninitialized refcount.

Fix this by always initializing this structure if the open was successful
but only do the extra get() if we got a lease.
This extra get() is only used to hold the structure until we get a lease
break from the server at which point we will kref_put() it during lease
processing.

Signed-off-by: Ronnie Sahlberg <lsahlber@redhat.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
CC: Stable <stable@vger.kernel.org>

diff --git a/fs/cifs/smb2ops.c b/fs/cifs/smb2ops.c
index 1022a3771e140d819e767ba5a75677a88d65f911..7cfafac255aadc157c74b6982e639701e6ba300a 100644 (file)
--- a/fs/cifs/smb2ops.c
+++ b/fs/cifs/smb2ops.c
@@ -717,20 +717,18 @@ int open_shroot(unsigned int xid, struct cifs_tcon *tcon, struct cifs_fid *pfid)
        oparms.fid->mid = le64_to_cpu(o_rsp->sync_hdr.MessageId);
 #endif /* CIFS_DEBUG2 */
 
-       if (o_rsp->OplockLevel == SMB2_OPLOCK_LEVEL_LEASE)
-               oplock = smb2_parse_lease_state(server, o_rsp,
-                                               &oparms.fid->epoch,
-                                               oparms.fid->lease_key);
-       else
-               goto oshr_exit;
-
-
        memcpy(tcon->crfid.fid, pfid, sizeof(struct cifs_fid));
        tcon->crfid.tcon = tcon;
        tcon->crfid.is_valid = true;
        kref_init(&tcon->crfid.refcount);
-       kref_get(&tcon->crfid.refcount);
 
+       if (o_rsp->OplockLevel == SMB2_OPLOCK_LEVEL_LEASE) {
+               kref_get(&tcon->crfid.refcount);
+               oplock = smb2_parse_lease_state(server, o_rsp,
+                                               &oparms.fid->epoch,
+                                               oparms.fid->lease_key);
+       } else
+               goto oshr_exit;
 
        qi_rsp = (struct smb2_query_info_rsp *)rsp_iov[1].iov_base;
        if (le32_to_cpu(qi_rsp->OutputBufferLength) < sizeof(struct smb2_file_all_info))