[bug,report] Handle mismatched open calls
diff mbox

Message ID 1491503047.8010.2.camel@redhat.com
State New
Headers show

Commit Message

Sachin Prabhu April 6, 2017, 6:24 p.m. UTC
On Thu, 2017-04-06 at 11:07 +0100, Sachin Prabhu wrote:
> On Thu, 2017-04-06 at 12:11 +0300, Dan Carpenter wrote:
> > Hello Sachin Prabhu,
> > 
> > The patch 96b75d0508f8: "Handle mismatched open calls" from Mar 3,
> > 2017, leads to the following static checker warning:
> > 
> > 	fs/cifs/cifssmb.c:1530 cifs_readv_receive()
> > 	error: potential NULL dereference 'server->smallbuf'.
> > 
> > fs/cifs/cifssmb.c
> >   1519          cifs_dbg(FYI, "0: iov_base=%p iov_len=%u\n",
> >   1520                   rdata->iov[0].iov_base, server-
> > >total_read);
> >   1521  
> >   1522          mid->resp_buf = server->smallbuf;
> >   1523          server->smallbuf = NULL;
> >                 ^^^^^^^^^^^^^^^^^^^^^^^
> > We set this to NULL here
> > 
> >   1524  
> >   1525          /* how much data is in the response? */
> >   1526          data_len = server->ops->read_data_length(buf);
> >   1527          if (data_offset + data_len > buflen) {
> >   1528                  /* data_len is corrupt -- discard frame */
> >   1529                  rdata->result = -EIO;
> >   1530                  return cifs_readv_discard(server, mid);
> >                                                   ^^^^^^
> > but we need it here.
> > 
> >   1531          }
> >   1532  
> >   1533          length = rdata->read_into_pages(server, rdata,
> > data_len);
> >   1534          if (length < 0)
> >   1535                  return length;
> > 
> > regards,
> > dan carpenter
> 
> Thanks Dan,
> 

Hello Dan,

I have attached a patch which replaces the original 
"Handle mismatched open calls" patch from the for-next branch.
Can you please run it against the static checker.

In the patch, we pass a buffer to cifs_discard_remaining_data() instead
of using server->small_buf to obtain the rfc len.

Thanks
Sachin Prabhu

Comments

Steve French April 7, 2017, 1:28 a.m. UTC | #1
merged into cifs-2-6.git - let me know if you see any problems with these ASAP

On Thu, Apr 6, 2017 at 1:24 PM, Sachin Prabhu <sprabhu@redhat.com> wrote:
> On Thu, 2017-04-06 at 11:07 +0100, Sachin Prabhu wrote:
>> On Thu, 2017-04-06 at 12:11 +0300, Dan Carpenter wrote:
>> > Hello Sachin Prabhu,
>> >
>> > The patch 96b75d0508f8: "Handle mismatched open calls" from Mar 3,
>> > 2017, leads to the following static checker warning:
>> >
>> >     fs/cifs/cifssmb.c:1530 cifs_readv_receive()
>> >     error: potential NULL dereference 'server->smallbuf'.
>> >
>> > fs/cifs/cifssmb.c
>> >   1519          cifs_dbg(FYI, "0: iov_base=%p iov_len=%u\n",
>> >   1520                   rdata->iov[0].iov_base, server-
>> > >total_read);
>> >   1521
>> >   1522          mid->resp_buf = server->smallbuf;
>> >   1523          server->smallbuf = NULL;
>> >                 ^^^^^^^^^^^^^^^^^^^^^^^
>> > We set this to NULL here
>> >
>> >   1524
>> >   1525          /* how much data is in the response? */
>> >   1526          data_len = server->ops->read_data_length(buf);
>> >   1527          if (data_offset + data_len > buflen) {
>> >   1528                  /* data_len is corrupt -- discard frame */
>> >   1529                  rdata->result = -EIO;
>> >   1530                  return cifs_readv_discard(server, mid);
>> >                                                   ^^^^^^
>> > but we need it here.
>> >
>> >   1531          }
>> >   1532
>> >   1533          length = rdata->read_into_pages(server, rdata,
>> > data_len);
>> >   1534          if (length < 0)
>> >   1535                  return length;
>> >
>> > regards,
>> > dan carpenter
>>
>> Thanks Dan,
>>
>
> Hello Dan,
>
> I have attached a patch which replaces the original
> "Handle mismatched open calls" patch from the for-next branch.
> Can you please run it against the static checker.
>
> In the patch, we pass a buffer to cifs_discard_remaining_data() instead
> of using server->small_buf to obtain the rfc len.
>
> Thanks
> Sachin Prabhu
Dan Carpenter April 7, 2017, 8:20 a.m. UTC | #2
Sure, that takes care of the static checker warning.  But then I had
all sorts of style nits to whinge-bucket about which you didn't ask
for...

On Thu, Apr 06, 2017 at 07:24:07PM +0100, Sachin Prabhu wrote:
> diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
> index 9ae695a..131663b 100644
> --- a/fs/cifs/connect.c
> +++ b/fs/cifs/connect.c
> @@ -904,10 +904,19 @@ cifs_demultiplex_thread(void *p)
>  
>  		server->lstrp = jiffies;
>  		if (mid_entry != NULL) {
> +			if ((mid_entry->mid_flags & MID_WAIT_CANCELLED) &&
> +			     mid_entry->mid_state == MID_RESPONSE_RECEIVED &&
> +					(server->ops->handle_cancelled_mid))

Extra parens are not required.  Please align it like this:

			if ((mid_entry->mid_flags & MID_WAIT_CANCELLED) &&
			     mid_entry->mid_state == MID_RESPONSE_RECEIVED &&
			     server->ops->handle_cancelled_mid)



> +				server->ops->handle_cancelled_mid(
> +							mid_entry->resp_buf,
> +							server);
> +
>  			if (!mid_entry->multiRsp || mid_entry->multiEnd)
>  				mid_entry->callback(mid_entry);
> -		} else if (!server->ops->is_oplock_break ||
> -			   !server->ops->is_oplock_break(buf, server)) {
> +		} else if (server->ops->is_oplock_break &&
> +			   server->ops->is_oplock_break(buf, server)) {
> +			cifs_dbg(FYI, "Received oplock break\n");
> +		} else {
>  			cifs_dbg(VFS, "No task to wake, unknown frame received! NumMids %d\n",
>  				 atomic_read(&midCount));
>  			cifs_dump_mem("Received Data is: ", buf,
> diff --git a/fs/cifs/smb2misc.c b/fs/cifs/smb2misc.c
> index fd516ea..f50e3ef 100644
> --- a/fs/cifs/smb2misc.c
> +++ b/fs/cifs/smb2misc.c
> @@ -659,3 +659,51 @@ smb2_is_valid_oplock_break(char *buffer, struct TCP_Server_Info *server)
>  	cifs_dbg(FYI, "Can not process oplock break for non-existent connection\n");
>  	return false;
>  }
> +
> +void
> +smb2_cancelled_close_fid(struct work_struct *work)
> +{
> +	struct close_cancelled_open *cancelled = container_of(work,
> +					struct close_cancelled_open, work);
> +
> +	cifs_dbg(VFS, "Close unmatched open\n");
> +
> +	SMB2_close(0, cancelled->tcon, cancelled->fid.persistent_fid,
> +					   cancelled->fid.volatile_fid);

Don't right align it.  Do it like this:

	SMB2_close(0, cancelled->tcon, cancelled->fid.persistent_fid,
		   cancelled->fid.volatile_fid);



> +	cifs_put_tcon(cancelled->tcon);
> +	kfree(cancelled);
> +}
> +
> +int
> +smb2_handle_cancelled_mid(char *buffer, struct TCP_Server_Info *server)
> +{
> +	struct smb2_sync_hdr *sync_hdr = get_sync_hdr(buffer);
> +	struct smb2_create_rsp *rsp = (struct smb2_create_rsp *)buffer;
> +	struct cifs_tcon *tcon;
> +	struct close_cancelled_open *cancelled;
> +
> +	if ((sync_hdr->Command != SMB2_CREATE) ||
> +		(sync_hdr->Status != STATUS_SUCCESS))

No need for extra parens.  Align it like this:

	if (sync_hdr->Command != SMB2_CREATE ||
	    sync_hdr->Status != STATUS_SUCCESS)
		return 0;



> +		return 0;
> +
> +	cancelled = (struct close_cancelled_open *)
> +			kzalloc(sizeof(struct close_cancelled_open),
> +				GFP_KERNEL);

No need to cast kzalloc.  Use sizeof(*cancelled).

	cancelled = kzalloc(sizeof(*cancelled), GFP_KERNEL);


> +	if (!cancelled)
> +		return -ENOMEM;
> +
> +	tcon = smb2_find_smb_tcon(server, sync_hdr->SessionId,
> +				  sync_hdr->TreeId);
> +	if (!tcon) {
> +		kfree(cancelled);
> +		return -ENOENT;
> +	}
> +
> +	cancelled->fid.persistent_fid = rsp->PersistentFileId;
> +	cancelled->fid.volatile_fid = rsp->VolatileFileId;
> +	cancelled->tcon = tcon;
> +	INIT_WORK(&cancelled->work, smb2_cancelled_close_fid);
> +	queue_work(cifsiod_wq, &cancelled->work);
> +
> +	return 0;
> +}

[ snip ]

> diff --git a/fs/cifs/smb2transport.c b/fs/cifs/smb2transport.c
> index 7c3bb1b..e3c8a9c 100644
> --- a/fs/cifs/smb2transport.c
> +++ b/fs/cifs/smb2transport.c
> @@ -115,23 +115,72 @@ smb3_crypto_shash_allocate(struct TCP_Server_Info *server)
>  	return 0;
>  }
>  
> -struct cifs_ses *
> -smb2_find_smb_ses(struct TCP_Server_Info *server, __u64 ses_id)
> +static struct cifs_ses *
> +_smb2_find_smb_ses(struct TCP_Server_Info *server, __u64 ses_id)

Could you name this "locked" or something and get rid of the _
underscore prefix?

>  {
>  	struct cifs_ses *ses;
>  
> -	spin_lock(&cifs_tcp_ses_lock);
>  	list_for_each_entry(ses, &server->smb_ses_list, smb_ses_list) {
>  		if (ses->Suid != ses_id)
>  			continue;
> -		spin_unlock(&cifs_tcp_ses_lock);
>  		return ses;
>  	}
> +
> +	return NULL;
> +}
> +
> +struct cifs_ses *
> +smb2_find_smb_ses(struct TCP_Server_Info *server, __u64 ses_id)
> +{
> +	struct cifs_ses *ses;
> +
> +	spin_lock(&cifs_tcp_ses_lock);
> +	ses = _smb2_find_smb_ses(server, ses_id);
>  	spin_unlock(&cifs_tcp_ses_lock);
>  
> +	return ses;
> +}
> +
> +static struct cifs_tcon *
> +_smb2_find_smb_sess_tcon(struct cifs_ses *ses, __u32  tid)

Just leave out the _ underscore prefix.  This is a static function so
there aren't that many users and they presumably know the locking rules.
For smb2_find_smb_ses we have a locked and unlocked version of the
function so it makes sense to put that in the name but here there is
no need I think.

> +{
> +	struct list_head *tmp;
> +	struct cifs_tcon *tcon;
> +
> +	list_for_each(tmp, &ses->tcon_list) {
> +		tcon = list_entry(tmp, struct cifs_tcon, tcon_list);

list_for_each_entry()?

> +		if (tcon->tid != tid)
> +			continue;
> +		++tcon->tc_count;
> +		return tcon;
> +	}
> +
>  	return NULL;
>  }
>  
> +/*
> + * Obtain tcon corresponding to the tid in the given
> + * cifs_ses
> + */
> +
> +struct cifs_tcon *
> +smb2_find_smb_tcon(struct TCP_Server_Info *server, __u64 ses_id, __u32  tid)
> +{
> +	struct cifs_ses *ses;
> +	struct cifs_tcon *tcon;
> +
> +	spin_lock(&cifs_tcp_ses_lock);
> +	ses = _smb2_find_smb_ses(server, ses_id);
> +	if (!ses) {
> +		spin_unlock(&cifs_tcp_ses_lock);
> +		return NULL;
> +	}
> +	tcon = _smb2_find_smb_sess_tcon(ses, tid);
> +	spin_unlock(&cifs_tcp_ses_lock);
> +
> +	return tcon;
> +}
> +
>  int
>  smb2_calc_signature(struct smb_rqst *rqst, struct TCP_Server_Info *server)
>  {
> @@ -511,6 +560,7 @@ smb2_mid_entry_alloc(const struct smb2_sync_hdr *shdr,
>  
>  	atomic_inc(&midCount);
>  	temp->mid_state = MID_REQUEST_ALLOCATED;
> +	temp->mid_flags = 0;

No need.  We already memset() this to zero.

>  	return temp;
>  }
>  
> diff --git a/fs/cifs/transport.c b/fs/cifs/transport.c
> index 526f053..d82a4ae 100644
> --- a/fs/cifs/transport.c
> +++ b/fs/cifs/transport.c
> @@ -752,9 +752,12 @@ cifs_send_recv(const unsigned int xid, struct cifs_ses *ses,
>  
>  	rc = wait_for_response(ses->server, midQ);
>  	if (rc != 0) {
> +		cifs_dbg(FYI, "Cancelling wait for mid %lu\n",
> +				(unsigned long)midQ->mid);

->mid is u64.  Just do this:

		cifs_dbg(FYI, "Cancelling wait for mid %llu\n", midQ->mid);


>  		send_cancel(ses->server, rqst, midQ);
>  		spin_lock(&GlobalMid_Lock);
>  		if (midQ->mid_state == MID_REQUEST_SUBMITTED) {
> +			midQ->mid_flags |= MID_WAIT_CANCELLED;
>  			midQ->callback = DeleteMidQEntry;
>  			spin_unlock(&GlobalMid_Lock);
>  			add_credits(ses->server, 1, optype);

regards,
dan carpenter
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Patch
diff mbox

From 83f1e5cca033c358b98ebc53389787dfa9051934 Mon Sep 17 00:00:00 2001
From: Sachin Prabhu <sprabhu@redhat.com>
Date: Fri, 3 Mar 2017 15:41:38 -0800
Subject: [PATCH] Handle mismatched open calls

A signal can interrupt a SendReceive call which result in incoming
responses to the call being ignored. This is a problem for calls such as
open which results in the successful response being ignored. This
results in an open file resource on the server.

The patch looks into responses which were cancelled after being sent and
in case of successful open closes the open fids.

For this patch, the check is only done in SendReceive2()

RH-bz: 1403319

v2: Search for sess and tcon while under spinlock
v3: Allocate struct cancelled before we pick the tcon
v4: Rebase against latest upstream.
v5: Fix oops caused by async reads
v6: Pass buffer to cifs_discard_remaining_data()

Signed-off-by: Sachin Prabhu <sprabhu@redhat.com>
Reviewed-by: Pavel Shilovsky <pshilov@microsoft.com>
Cc: Stable <stable@vger.kernel.org>
---
 fs/cifs/cifsglob.h      | 11 ++++++++++
 fs/cifs/cifsproto.h     |  3 ++-
 fs/cifs/cifssmb.c       | 11 ++++++----
 fs/cifs/connect.c       | 13 +++++++++--
 fs/cifs/smb2misc.c      | 48 ++++++++++++++++++++++++++++++++++++++++
 fs/cifs/smb2ops.c       |  8 +++++--
 fs/cifs/smb2proto.h     |  7 ++++++
 fs/cifs/smb2transport.c | 58 +++++++++++++++++++++++++++++++++++++++++++++----
 fs/cifs/transport.c     |  3 +++
 9 files changed, 149 insertions(+), 13 deletions(-)

diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h
index c565e0db..d07f13a 100644
--- a/fs/cifs/cifsglob.h
+++ b/fs/cifs/cifsglob.h
@@ -243,6 +243,7 @@  struct smb_version_operations {
 	/* verify the message */
 	int (*check_message)(char *, unsigned int, struct TCP_Server_Info *);
 	bool (*is_oplock_break)(char *, struct TCP_Server_Info *);
+	int (*handle_cancelled_mid)(char *, struct TCP_Server_Info *);
 	void (*downgrade_oplock)(struct TCP_Server_Info *,
 					struct cifsInodeInfo *, bool);
 	/* process transaction2 response */
@@ -1344,6 +1345,7 @@  struct mid_q_entry {
 	void *callback_data;	  /* general purpose pointer for callback */
 	void *resp_buf;		/* pointer to received SMB header */
 	int mid_state;	/* wish this were enum but can not pass to wait_event */
+	unsigned int mid_flags;
 	__le16 command;		/* smb command code */
 	bool large_buf:1;	/* if valid response, is pointer to large buf */
 	bool multiRsp:1;	/* multiple trans2 responses for one request  */
@@ -1351,6 +1353,12 @@  struct mid_q_entry {
 	bool decrypted:1;	/* decrypted entry */
 };
 
+struct close_cancelled_open {
+	struct cifs_fid         fid;
+	struct cifs_tcon        *tcon;
+	struct work_struct      work;
+};
+
 /*	Make code in transport.c a little cleaner by moving
 	update of optional stats into function below */
 #ifdef CONFIG_CIFS_STATS2
@@ -1482,6 +1490,9 @@  static inline void free_dfs_info_array(struct dfs_info3_param *param,
 #define   MID_RESPONSE_MALFORMED 0x10
 #define   MID_SHUTDOWN		 0x20
 
+/* Flags */
+#define   MID_WAIT_CANCELLED	 1 /* Cancelled while waiting for response */
+
 /* Types of response buffer returned from SendReceive2 */
 #define   CIFS_NO_BUFFER        0    /* Response buffer not returned */
 #define   CIFS_SMALL_BUFFER     1
diff --git a/fs/cifs/cifsproto.h b/fs/cifs/cifsproto.h
index 97e5d23..ec5e5e5 100644
--- a/fs/cifs/cifsproto.h
+++ b/fs/cifs/cifsproto.h
@@ -79,7 +79,8 @@  extern void cifs_delete_mid(struct mid_q_entry *mid);
 extern void cifs_wake_up_task(struct mid_q_entry *mid);
 extern int cifs_handle_standard(struct TCP_Server_Info *server,
 				struct mid_q_entry *mid);
-extern int cifs_discard_remaining_data(struct TCP_Server_Info *server);
+extern int cifs_discard_remaining_data(struct TCP_Server_Info *server,
+				       char *buf);
 extern int cifs_call_async(struct TCP_Server_Info *server,
 			struct smb_rqst *rqst,
 			mid_receive_t *receive, mid_callback_t *callback,
diff --git a/fs/cifs/cifssmb.c b/fs/cifs/cifssmb.c
index 0669506..967b9263 100644
--- a/fs/cifs/cifssmb.c
+++ b/fs/cifs/cifssmb.c
@@ -1400,9 +1400,9 @@  CIFS_open(const unsigned int xid, struct cifs_open_parms *oparms, int *oplock,
  * current bigbuf.
  */
 int
-cifs_discard_remaining_data(struct TCP_Server_Info *server)
+cifs_discard_remaining_data(struct TCP_Server_Info *server, char *buf)
 {
-	unsigned int rfclen = get_rfc1002_length(server->smallbuf);
+	unsigned int rfclen = get_rfc1002_length(buf);
 	int remaining = rfclen + 4 - server->total_read;
 
 	while (remaining > 0) {
@@ -1426,7 +1426,7 @@  cifs_readv_discard(struct TCP_Server_Info *server, struct mid_q_entry *mid)
 	int length;
 	struct cifs_readdata *rdata = mid->callback_data;
 
-	length = cifs_discard_remaining_data(server);
+	length = cifs_discard_remaining_data(server, mid->resp_buf);
 	dequeue_mid(mid, rdata->result);
 	return length;
 }
@@ -1459,7 +1459,7 @@  cifs_readv_receive(struct TCP_Server_Info *server, struct mid_q_entry *mid)
 
 	if (server->ops->is_status_pending &&
 	    server->ops->is_status_pending(buf, server, 0)) {
-		cifs_discard_remaining_data(server);
+		cifs_discard_remaining_data(server, buf);
 		return -1;
 	}
 
@@ -1519,6 +1519,9 @@  cifs_readv_receive(struct TCP_Server_Info *server, struct mid_q_entry *mid)
 	cifs_dbg(FYI, "0: iov_base=%p iov_len=%u\n",
 		 rdata->iov[0].iov_base, server->total_read);
 
+	mid->resp_buf = server->smallbuf;
+	server->smallbuf = NULL;
+
 	/* how much data is in the response? */
 	data_len = server->ops->read_data_length(buf);
 	if (data_offset + data_len > buflen) {
diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
index 9ae695a..131663b 100644
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -904,10 +904,19 @@  cifs_demultiplex_thread(void *p)
 
 		server->lstrp = jiffies;
 		if (mid_entry != NULL) {
+			if ((mid_entry->mid_flags & MID_WAIT_CANCELLED) &&
+			     mid_entry->mid_state == MID_RESPONSE_RECEIVED &&
+					(server->ops->handle_cancelled_mid))
+				server->ops->handle_cancelled_mid(
+							mid_entry->resp_buf,
+							server);
+
 			if (!mid_entry->multiRsp || mid_entry->multiEnd)
 				mid_entry->callback(mid_entry);
-		} else if (!server->ops->is_oplock_break ||
-			   !server->ops->is_oplock_break(buf, server)) {
+		} else if (server->ops->is_oplock_break &&
+			   server->ops->is_oplock_break(buf, server)) {
+			cifs_dbg(FYI, "Received oplock break\n");
+		} else {
 			cifs_dbg(VFS, "No task to wake, unknown frame received! NumMids %d\n",
 				 atomic_read(&midCount));
 			cifs_dump_mem("Received Data is: ", buf,
diff --git a/fs/cifs/smb2misc.c b/fs/cifs/smb2misc.c
index fd516ea..f50e3ef 100644
--- a/fs/cifs/smb2misc.c
+++ b/fs/cifs/smb2misc.c
@@ -659,3 +659,51 @@  smb2_is_valid_oplock_break(char *buffer, struct TCP_Server_Info *server)
 	cifs_dbg(FYI, "Can not process oplock break for non-existent connection\n");
 	return false;
 }
+
+void
+smb2_cancelled_close_fid(struct work_struct *work)
+{
+	struct close_cancelled_open *cancelled = container_of(work,
+					struct close_cancelled_open, work);
+
+	cifs_dbg(VFS, "Close unmatched open\n");
+
+	SMB2_close(0, cancelled->tcon, cancelled->fid.persistent_fid,
+					   cancelled->fid.volatile_fid);
+	cifs_put_tcon(cancelled->tcon);
+	kfree(cancelled);
+}
+
+int
+smb2_handle_cancelled_mid(char *buffer, struct TCP_Server_Info *server)
+{
+	struct smb2_sync_hdr *sync_hdr = get_sync_hdr(buffer);
+	struct smb2_create_rsp *rsp = (struct smb2_create_rsp *)buffer;
+	struct cifs_tcon *tcon;
+	struct close_cancelled_open *cancelled;
+
+	if ((sync_hdr->Command != SMB2_CREATE) ||
+		(sync_hdr->Status != STATUS_SUCCESS))
+		return 0;
+
+	cancelled = (struct close_cancelled_open *)
+			kzalloc(sizeof(struct close_cancelled_open),
+				GFP_KERNEL);
+	if (!cancelled)
+		return -ENOMEM;
+
+	tcon = smb2_find_smb_tcon(server, sync_hdr->SessionId,
+				  sync_hdr->TreeId);
+	if (!tcon) {
+		kfree(cancelled);
+		return -ENOENT;
+	}
+
+	cancelled->fid.persistent_fid = rsp->PersistentFileId;
+	cancelled->fid.volatile_fid = rsp->VolatileFileId;
+	cancelled->tcon = tcon;
+	INIT_WORK(&cancelled->work, smb2_cancelled_close_fid);
+	queue_work(cifsiod_wq, &cancelled->work);
+
+	return 0;
+}
diff --git a/fs/cifs/smb2ops.c b/fs/cifs/smb2ops.c
index 583a0e2..7b12a72 100644
--- a/fs/cifs/smb2ops.c
+++ b/fs/cifs/smb2ops.c
@@ -2195,7 +2195,7 @@  receive_encrypted_read(struct TCP_Server_Info *server, struct mid_q_entry **mid)
 	if (rc)
 		goto free_pages;
 
-	rc = cifs_discard_remaining_data(server);
+	rc = cifs_discard_remaining_data(server, buf);
 	if (rc)
 		goto free_pages;
 
@@ -2221,7 +2221,7 @@  receive_encrypted_read(struct TCP_Server_Info *server, struct mid_q_entry **mid)
 	kfree(pages);
 	return rc;
 discard_data:
-	cifs_discard_remaining_data(server);
+	cifs_discard_remaining_data(server, buf);
 	goto free_pages;
 }
 
@@ -2329,6 +2329,7 @@  struct smb_version_operations smb20_operations = {
 	.clear_stats = smb2_clear_stats,
 	.print_stats = smb2_print_stats,
 	.is_oplock_break = smb2_is_valid_oplock_break,
+	.handle_cancelled_mid = smb2_handle_cancelled_mid,
 	.downgrade_oplock = smb2_downgrade_oplock,
 	.need_neg = smb2_need_neg,
 	.negotiate = smb2_negotiate,
@@ -2411,6 +2412,7 @@  struct smb_version_operations smb21_operations = {
 	.clear_stats = smb2_clear_stats,
 	.print_stats = smb2_print_stats,
 	.is_oplock_break = smb2_is_valid_oplock_break,
+	.handle_cancelled_mid = smb2_handle_cancelled_mid,
 	.downgrade_oplock = smb2_downgrade_oplock,
 	.need_neg = smb2_need_neg,
 	.negotiate = smb2_negotiate,
@@ -2495,6 +2497,7 @@  struct smb_version_operations smb30_operations = {
 	.print_stats = smb2_print_stats,
 	.dump_share_caps = smb2_dump_share_caps,
 	.is_oplock_break = smb2_is_valid_oplock_break,
+	.handle_cancelled_mid = smb2_handle_cancelled_mid,
 	.downgrade_oplock = smb2_downgrade_oplock,
 	.need_neg = smb2_need_neg,
 	.negotiate = smb2_negotiate,
@@ -2589,6 +2592,7 @@  struct smb_version_operations smb311_operations = {
 	.print_stats = smb2_print_stats,
 	.dump_share_caps = smb2_dump_share_caps,
 	.is_oplock_break = smb2_is_valid_oplock_break,
+	.handle_cancelled_mid = smb2_handle_cancelled_mid,
 	.downgrade_oplock = smb2_downgrade_oplock,
 	.need_neg = smb2_need_neg,
 	.negotiate = smb2_negotiate,
diff --git a/fs/cifs/smb2proto.h b/fs/cifs/smb2proto.h
index 69e3587..6853454 100644
--- a/fs/cifs/smb2proto.h
+++ b/fs/cifs/smb2proto.h
@@ -48,6 +48,10 @@  extern struct mid_q_entry *smb2_setup_request(struct cifs_ses *ses,
 			      struct smb_rqst *rqst);
 extern struct mid_q_entry *smb2_setup_async_request(
 			struct TCP_Server_Info *server, struct smb_rqst *rqst);
+extern struct cifs_ses *smb2_find_smb_ses(struct TCP_Server_Info *server,
+					   __u64 ses_id);
+extern struct cifs_tcon *smb2_find_smb_tcon(struct TCP_Server_Info *server,
+						__u64 ses_id, __u32  tid);
 extern int smb2_calc_signature(struct smb_rqst *rqst,
 				struct TCP_Server_Info *server);
 extern int smb3_calc_signature(struct smb_rqst *rqst,
@@ -164,6 +168,9 @@  extern int SMB2_set_compression(const unsigned int xid, struct cifs_tcon *tcon,
 extern int SMB2_oplock_break(const unsigned int xid, struct cifs_tcon *tcon,
 			     const u64 persistent_fid, const u64 volatile_fid,
 			     const __u8 oplock_level);
+extern int smb2_handle_cancelled_mid(char *buffer,
+					struct TCP_Server_Info *server);
+void smb2_cancelled_close_fid(struct work_struct *work);
 extern int SMB2_QFS_info(const unsigned int xid, struct cifs_tcon *tcon,
 			 u64 persistent_file_id, u64 volatile_file_id,
 			 struct kstatfs *FSData);
diff --git a/fs/cifs/smb2transport.c b/fs/cifs/smb2transport.c
index 7c3bb1b..e3c8a9c 100644
--- a/fs/cifs/smb2transport.c
+++ b/fs/cifs/smb2transport.c
@@ -115,23 +115,72 @@  smb3_crypto_shash_allocate(struct TCP_Server_Info *server)
 	return 0;
 }
 
-struct cifs_ses *
-smb2_find_smb_ses(struct TCP_Server_Info *server, __u64 ses_id)
+static struct cifs_ses *
+_smb2_find_smb_ses(struct TCP_Server_Info *server, __u64 ses_id)
 {
 	struct cifs_ses *ses;
 
-	spin_lock(&cifs_tcp_ses_lock);
 	list_for_each_entry(ses, &server->smb_ses_list, smb_ses_list) {
 		if (ses->Suid != ses_id)
 			continue;
-		spin_unlock(&cifs_tcp_ses_lock);
 		return ses;
 	}
+
+	return NULL;
+}
+
+struct cifs_ses *
+smb2_find_smb_ses(struct TCP_Server_Info *server, __u64 ses_id)
+{
+	struct cifs_ses *ses;
+
+	spin_lock(&cifs_tcp_ses_lock);
+	ses = _smb2_find_smb_ses(server, ses_id);
 	spin_unlock(&cifs_tcp_ses_lock);
 
+	return ses;
+}
+
+static struct cifs_tcon *
+_smb2_find_smb_sess_tcon(struct cifs_ses *ses, __u32  tid)
+{
+	struct list_head *tmp;
+	struct cifs_tcon *tcon;
+
+	list_for_each(tmp, &ses->tcon_list) {
+		tcon = list_entry(tmp, struct cifs_tcon, tcon_list);
+		if (tcon->tid != tid)
+			continue;
+		++tcon->tc_count;
+		return tcon;
+	}
+
 	return NULL;
 }
 
+/*
+ * Obtain tcon corresponding to the tid in the given
+ * cifs_ses
+ */
+
+struct cifs_tcon *
+smb2_find_smb_tcon(struct TCP_Server_Info *server, __u64 ses_id, __u32  tid)
+{
+	struct cifs_ses *ses;
+	struct cifs_tcon *tcon;
+
+	spin_lock(&cifs_tcp_ses_lock);
+	ses = _smb2_find_smb_ses(server, ses_id);
+	if (!ses) {
+		spin_unlock(&cifs_tcp_ses_lock);
+		return NULL;
+	}
+	tcon = _smb2_find_smb_sess_tcon(ses, tid);
+	spin_unlock(&cifs_tcp_ses_lock);
+
+	return tcon;
+}
+
 int
 smb2_calc_signature(struct smb_rqst *rqst, struct TCP_Server_Info *server)
 {
@@ -511,6 +560,7 @@  smb2_mid_entry_alloc(const struct smb2_sync_hdr *shdr,
 
 	atomic_inc(&midCount);
 	temp->mid_state = MID_REQUEST_ALLOCATED;
+	temp->mid_flags = 0;
 	return temp;
 }
 
diff --git a/fs/cifs/transport.c b/fs/cifs/transport.c
index 526f053..d82a4ae 100644
--- a/fs/cifs/transport.c
+++ b/fs/cifs/transport.c
@@ -752,9 +752,12 @@  cifs_send_recv(const unsigned int xid, struct cifs_ses *ses,
 
 	rc = wait_for_response(ses->server, midQ);
 	if (rc != 0) {
+		cifs_dbg(FYI, "Cancelling wait for mid %lu\n",
+				(unsigned long)midQ->mid);
 		send_cancel(ses->server, rqst, midQ);
 		spin_lock(&GlobalMid_Lock);
 		if (midQ->mid_state == MID_REQUEST_SUBMITTED) {
+			midQ->mid_flags |= MID_WAIT_CANCELLED;
 			midQ->callback = DeleteMidQEntry;
 			spin_unlock(&GlobalMid_Lock);
 			add_credits(ses->server, 1, optype);
-- 
2.9.3