[PATCH AUTOSEL 5.1 062/186] cifs: fix credits leak for SMB1 oplock breaks

[Sasha Levin]

From: Ronnie Sahlberg <lsahlber@xxxxxxxxxx>

[ Upstream commit d69cb728e70c40268762182a62f5d5d6fa51c5b2 ]

For SMB1 oplock breaks we would grab one credit while sending the PDU
but we would never relese the credit back since we will never receive a
response to this from the server. Eventuallt this would lead to a hang
once all credits are leaked.

Fix this by defining a new flag CIFS_NO_SRV_RSP which indicates that there
is no server response to this command and thus we need to add any credits back
immediately after sending the PDU.

CC: Stable <stable@xxxxxxxxxxxxxxx> #v5.0+
Signed-off-by: Ronnie Sahlberg <lsahlber@xxxxxxxxxx>
Reviewed-by: Pavel Shilovsky <pshilov@xxxxxxxxxxxxx>
Signed-off-by: Steve French <stfrench@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 fs/cifs/cifsglob.h  |  1 +
 fs/cifs/cifssmb.c   |  2 +-
 fs/cifs/transport.c | 10 +++++-----
 3 files changed, 7 insertions(+), 6 deletions(-)

diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h
index 585ad3207cb12..607468948f72b 100644
--- a/fs/cifs/cifsglob.h
+++ b/fs/cifs/cifsglob.h
@@ -1687,6 +1687,7 @@ static inline bool is_retryable_error(int error)
 
 #define   CIFS_HAS_CREDITS 0x0400    /* already has credits */
 #define   CIFS_TRANSFORM_REQ 0x0800    /* transform request before sending */
+#define   CIFS_NO_SRV_RSP    0x1000    /* there is no server response */
 
 /* Security Flags: indicate type of session setup needed */
 #define   CIFSSEC_MAY_SIGN	0x00001
diff --git a/fs/cifs/cifssmb.c b/fs/cifs/cifssmb.c
index f43747c062a70..6050851edcb82 100644
--- a/fs/cifs/cifssmb.c
+++ b/fs/cifs/cifssmb.c
@@ -2540,7 +2540,7 @@ CIFSSMBLock(const unsigned int xid, struct cifs_tcon *tcon,
 
 	if (lockType == LOCKING_ANDX_OPLOCK_RELEASE) {
 		/* no response expected */
-		flags = CIFS_ASYNC_OP | CIFS_OBREAK_OP;
+		flags = CIFS_NO_SRV_RSP | CIFS_ASYNC_OP | CIFS_OBREAK_OP;
 		pSMB->Timeout = 0;
 	} else if (waitFlag) {
 		flags = CIFS_BLOCKING_OP; /* blocking operation, no timeout */
diff --git a/fs/cifs/transport.c b/fs/cifs/transport.c
index 1de8e996e566f..72e242c49ca11 100644
--- a/fs/cifs/transport.c
+++ b/fs/cifs/transport.c
@@ -1054,8 +1054,11 @@ compound_send_recv(const unsigned int xid, struct cifs_ses *ses,
 
 	mutex_unlock(&ses->server->srv_mutex);
 
-	if (rc < 0) {
-		/* Sending failed for some reason - return credits back */
+	/*
+	 * If sending failed for some reason or it is an oplock break that we
+	 * will not receive a response to - return credits back
+	 */
+	if (rc < 0 || (flags & CIFS_NO_SRV_RSP)) {
 		for (i = 0; i < num_rqst; i++)
 			add_credits(ses->server, &credits[i], optype);
 		goto out;
@@ -1076,9 +1079,6 @@ compound_send_recv(const unsigned int xid, struct cifs_ses *ses,
 		smb311_update_preauth_hash(ses, rqst[0].rq_iov,
 					   rqst[0].rq_nvec);
 
-	if ((flags & CIFS_TIMEOUT_MASK) == CIFS_ASYNC_OP)
-		goto out;
-
 	for (i = 0; i < num_rqst; i++) {
 		rc = wait_for_response(ses->server, midQ[i]);
 		if (rc != 0)
-- 
2.20.1