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

Sasha Levin
2019-06-01T13:41:42Z

From: Ronnie Sahlberg <lsahlber@redhat.com>

[ 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@vger.kernel.org> #v5.0+
Signed-off-by: Ronnie Sahlberg <lsahlber@redhat.com>
Reviewed-by: Pavel Shilovsky <pshilov@microsoft.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
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