cifs: Fix potential softlockups while refreshing DFS cache

We used to skip reconnects on all SMB2_IOCTL commands due to SMB3+
FSCTL_VALIDATE_NEGOTIATE_INFO - which made sense since we're still
establishing a SMB session.

However, when refresh_cache_worker() calls smb2_get_dfs_refer() and
we're under reconnect, SMB2_ioctl() will not be able to get a proper
status error (e.g. -EHOSTDOWN in case we failed to reconnect) but an
-EAGAIN from cifs_send_recv() thus looping forever in
refresh_cache_worker().

Fixes: e99c63e4d86d ("SMB3: Fix deadlock in validate negotiate hits reconnect")
Signed-off-by: Paulo Alcantara (SUSE) <pc@cjr.nz>
Suggested-by: Aurelien Aptel <aaptel@suse.com>
Reviewed-by: Aurelien Aptel <aaptel@suse.com>
Signed-off-by: Steve French <stfrench@microsoft.com>

diff --git a/fs/cifs/smb2pdu.c b/fs/cifs/smb2pdu.c
index 9f3c40b..ed77f94 100644 (file)
--- a/fs/cifs/smb2pdu.c
+++ b/fs/cifs/smb2pdu.c
@@ -252,7 +252,7 @@ smb2_reconnect(__le16 smb2_command, struct cifs_tcon *tcon)
        if (tcon == NULL)
                return 0;
 
-       if (smb2_command == SMB2_TREE_CONNECT || smb2_command == SMB2_IOCTL)
+       if (smb2_command == SMB2_TREE_CONNECT)
                return 0;
 
        if (tcon->tidStatus == CifsExiting) {
@@ -426,16 +426,9 @@ fill_small_buf(__le16 smb2_command, struct cifs_tcon *tcon, void *buf,
  * SMB information in the SMB header. If the return code is zero, this
  * function must have filled in request_buf pointer.
  */
-static int
-smb2_plain_req_init(__le16 smb2_command, struct cifs_tcon *tcon,
-                   void **request_buf, unsigned int *total_len)
+static int __smb2_plain_req_init(__le16 smb2_command, struct cifs_tcon *tcon,
+                                 void **request_buf, unsigned int *total_len)
 {
-       int rc;
-
-       rc = smb2_reconnect(smb2_command, tcon);
-       if (rc)
-               return rc;
-
        /* BB eventually switch this to SMB2 specific small buf size */
        if (smb2_command == SMB2_SET_INFO)
                *request_buf = cifs_buf_get();
@@ -456,7 +449,31 @@ smb2_plain_req_init(__le16 smb2_command, struct cifs_tcon *tcon,
                cifs_stats_inc(&tcon->num_smbs_sent);
        }
 
-       return rc;
+       return 0;
+}
+
+static int smb2_plain_req_init(__le16 smb2_command, struct cifs_tcon *tcon,
+                              void **request_buf, unsigned int *total_len)
+{
+       int rc;
+
+       rc = smb2_reconnect(smb2_command, tcon);
+       if (rc)
+               return rc;
+
+       return __smb2_plain_req_init(smb2_command, tcon, request_buf,
+                                    total_len);
+}
+
+static int smb2_ioctl_req_init(u32 opcode, struct cifs_tcon *tcon,
+                              void **request_buf, unsigned int *total_len)
+{
+       /* Skip reconnect only for FSCTL_VALIDATE_NEGOTIATE_INFO IOCTLs */
+       if (opcode == FSCTL_VALIDATE_NEGOTIATE_INFO) {
+               return __smb2_plain_req_init(SMB2_IOCTL, tcon, request_buf,
+                                            total_len);
+       }
+       return smb2_plain_req_init(SMB2_IOCTL, tcon, request_buf, total_len);
 }
 
 /* For explanation of negotiate contexts see MS-SMB2 section 2.2.3.1 */
@@ -2686,7 +2703,7 @@ SMB2_ioctl_init(struct cifs_tcon *tcon, struct smb_rqst *rqst,
        int rc;
        char *in_data_buf;
 
-       rc = smb2_plain_req_init(SMB2_IOCTL, tcon, (void **) &req, &total_len);
+       rc = smb2_ioctl_req_init(opcode, tcon, (void **) &req, &total_len);
        if (rc)
                return rc;