linux-kernel - [PATCH 5.1 046/122] cifs: fix credits leak for SMB1 oplock breaks

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Date:   Thu, 23 May 2019 21:06:08 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Ronnie Sahlberg <lsahlber@...hat.com>,
        Pavel Shilovsky <pshilov@...rosoft.com>,
        Steve French <stfrench@...rosoft.com>
Subject: [PATCH 5.1 046/122] cifs: fix credits leak for SMB1 oplock breaks

From: Ronnie Sahlberg <lsahlber@...hat.com>

commit d69cb728e70c40268762182a62f5d5d6fa51c5b2 upstream.

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@...r.kernel.org> #v5.0+
Signed-off-by: Ronnie Sahlberg <lsahlber@...hat.com>
Reviewed-by: Pavel Shilovsky <pshilov@...rosoft.com>
Signed-off-by: Steve French <stfrench@...rosoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 fs/cifs/cifsglob.h  |    1 +
 fs/cifs/cifssmb.c   |    2 +-
 fs/cifs/transport.c |   10 +++++-----
 3 files changed, 7 insertions(+), 6 deletions(-)

--- a/fs/cifs/cifsglob.h
+++ b/fs/cifs/cifsglob.h
@@ -1687,6 +1687,7 @@ static inline bool is_retryable_error(in
 
 #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
--- a/fs/cifs/cifssmb.c
+++ b/fs/cifs/cifssmb.c
@@ -2540,7 +2540,7 @@ CIFSSMBLock(const unsigned int xid, stru
 
 	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 */
--- a/fs/cifs/transport.c
+++ b/fs/cifs/transport.c
@@ -1054,8 +1054,11 @@ compound_send_recv(const unsigned int xi
 
 	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 xi
 		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)