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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: e99c63e4d8 ("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>
This commit is contained in:
Paulo Alcantara (SUSE) 2019-11-22 12:30:53 -03:00 committed by Steve French
parent df3df923b3
commit 84a1f5b1cc
1 changed files with 29 additions and 12 deletions
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41
fs/cifs/smb2pdu.c
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@ -252,7 +252,7 @@ smb2_reconnect(__le16 smb2_command, struct cifs_tcon *tcon)
if (tcon == NULL) if (tcon == NULL)
return 0; return 0;
if (smb2_command == SMB2_TREE_CONNECT || smb2_command == SMB2_IOCTL) if (smb2_command == SMB2_TREE_CONNECT)
return 0; return 0;
if (tcon->tidStatus == CifsExiting) { 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 * SMB information in the SMB header. If the return code is zero, this
* function must have filled in request_buf pointer. * function must have filled in request_buf pointer.
*/ */
static int static int __smb2_plain_req_init(__le16 smb2_command, struct cifs_tcon *tcon,
smb2_plain_req_init(__le16 smb2_command, struct cifs_tcon *tcon, void **request_buf, unsigned int *total_len)
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 */ /* BB eventually switch this to SMB2 specific small buf size */
if (smb2_command == SMB2_SET_INFO) if (smb2_command == SMB2_SET_INFO)
*request_buf = cifs_buf_get(); *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); 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 */ /* 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; int rc;
char *in_data_buf; 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) if (rc)
return rc; return rc;