[CIFS] Ensure that cifs multiplex ids do not collide.

Signed-off-by: Steve French (sfrench@us.ibm.com)

fs/cifs/cifsglob.h

@@ -147,6 +147,7 @@ struct TCP_Server_Info {
 	/* (returned on Negotiate */
 	int capabilities; /* allow selective disabling of caps by smb sess */
 	__u16 timeZone;
+	__u16 CurrentMid;         /* multiplex id - rotating counter */
 	char cryptKey[CIFS_CRYPTO_KEY_SIZE];
 	char workstation_RFC1001_name[16]; /* 16th byte is always zero */
 	__u32 sequence_number; /* needed for CIFS PDU signature */

fs/cifs/cifspdu.h

@@ -1961,18 +1961,17 @@ struct data_blob {
 	perhaps add a CreateDevice - to create Pipes and other special .inodes
 	Also note POSIX open flags
 	2) Close - to return the last write time to do cache across close more safely
-	3) PosixQFSInfo - to return statfs info
-	4) FindFirst return unique inode number - what about resume key, two forms short (matches readdir) and full (enough info to cache inodes)
-	5) Mkdir - set mode
+	3) FindFirst return unique inode number - what about resume key, two 
+	forms short (matches readdir) and full (enough info to cache inodes)
+	4) Mkdir - set mode
 	
 	And under consideration: 
-	6) FindClose2 (return nanosecond timestamp ??)
-	7) Use nanosecond timestamps throughout all time fields if 
+	5) FindClose2 (return nanosecond timestamp ??)
+	6) Use nanosecond timestamps throughout all time fields if 
 	   corresponding attribute flag is set
-	8) sendfile - handle based copy
-	9) Direct i/o
-	10) "POSIX ACL" support
-	11) Misc fcntls?
+	7) sendfile - handle based copy
+	8) Direct i/o
+	9) Misc fcntls?
 	
 	what about fixing 64 bit alignment
 	
@@ -2028,7 +2027,7 @@ struct data_blob {
 	
  */
 
-/* xsymlink is a symlink format that can be used
+/* xsymlink is a symlink format (used by MacOS) that can be used
    to save symlink info in a regular file when 
    mounted to operating systems that do not
    support the cifs Unix extensions or EAs (for xattr

fs/cifs/cifsproto.h

@@ -61,9 +61,9 @@ extern int decode_negTokenInit(unsigned char *security_blob, int length,
 extern int cifs_inet_pton(int, char * source, void *dst);
 extern int map_smb_to_linux_error(struct smb_hdr *smb);
 extern void header_assemble(struct smb_hdr *, char /* command */ ,
-			const struct cifsTconInfo *, int /* specifies length
-			    of fixed section (word count) in two byte units */
-			);
+			    const struct cifsTconInfo *, int /* length of
+			    fixed section (word count) in two byte units */);
+extern __u16 GetNextMid(struct TCP_Server_Info *server);
 extern struct oplock_q_entry * AllocOplockQEntry(struct inode *, u16, 
 						 struct cifsTconInfo *);
 extern void DeleteOplockQEntry(struct oplock_q_entry *);

fs/cifs/cifssmb.c

@@ -330,7 +330,7 @@ CIFSSMBNegotiate(unsigned int xid, struct cifsSesInfo *ses)
 		      (void **) &pSMB, (void **) &pSMBr);
 	if (rc)
 		return rc;
-
+	pSMB->hdr.Mid = GetNextMid(server);
 	pSMB->hdr.Flags2 |= SMBFLG2_UNICODE;
 	if (extended_security)
 		pSMB->hdr.Flags2 |= SMBFLG2_EXT_SEC;
@@ -415,15 +415,14 @@ CIFSSMBNegotiate(unsigned int xid, struct cifsSesInfo *ses)
 			if(server->secMode & SECMODE_SIGN_REQUIRED)
 				cERROR(1,
 				 ("Server requires /proc/fs/cifs/PacketSigningEnabled"));
-			server->secMode &= ~(SECMODE_SIGN_ENABLED | 
-							SECMODE_SIGN_REQUIRED);
+			server->secMode &= ~(SECMODE_SIGN_ENABLED | SECMODE_SIGN_REQUIRED);
 		} else if(sign_CIFS_PDUs == 1) {
 			if((server->secMode & SECMODE_SIGN_REQUIRED) == 0)
-				server->secMode &= ~(SECMODE_SIGN_ENABLED |
-							 SECMODE_SIGN_REQUIRED);
+				server->secMode &= ~(SECMODE_SIGN_ENABLED | SECMODE_SIGN_REQUIRED);
 		}
 				
 	}
+	
 	cifs_buf_release(pSMB);
 	return rc;
 }
@@ -519,6 +518,8 @@ CIFSSMBLogoff(const int xid, struct cifsSesInfo *ses)
 	smb_buffer_response = (struct smb_hdr *)pSMB; /* BB removeme BB */
 	
 	if(ses->server) {
+		pSMB->hdr.Mid = GetNextMid(ses->server);
+
 		if(ses->server->secMode & 
 		   (SECMODE_SIGN_REQUIRED | SECMODE_SIGN_ENABLED))
 			pSMB->hdr.Flags2 |= SMBFLG2_SECURITY_SIGNATURE;
@@ -2519,11 +2520,12 @@ findFirstRetry:
 	rc = SendReceive(xid, tcon->ses, (struct smb_hdr *) pSMB,
 			 (struct smb_hdr *) pSMBr, &bytes_returned, 0);
 
-	if (rc) {/* BB add logic to retry regular search if Unix search 
-			rejected unexpectedly by server */
+	if (rc) {/* BB add logic to retry regular search if Unix search rejected unexpectedly by server */
 		/* BB Add code to handle unsupported level rc */
 		cFYI(1, ("Error in FindFirst = %d", rc));
-		cifs_buf_release(pSMB);
+
+		if (pSMB)
+			cifs_buf_release(pSMB);
 
 		/* BB eventually could optimize out free and realloc of buf */
 		/*    for this case */
@@ -2857,7 +2859,10 @@ getDFSRetry:
 		      (void **) &pSMBr);
 	if (rc)
 		return rc;
-
+	
+	/* server pointer checked in called function, 
+	but should never be null here anyway */
+	pSMB->hdr.Mid = GetNextMid(ses->server);
 	pSMB->hdr.Tid = ses->ipc_tid;
 	pSMB->hdr.Uid = ses->Suid;
 	if (ses->capabilities & CAP_STATUS32) {

fs/cifs/connect.c

@@ -1857,6 +1857,7 @@ CIFSSessSetup(unsigned int xid, struct cifsSesInfo *ses,
 	header_assemble(smb_buffer, SMB_COM_SESSION_SETUP_ANDX,
 			NULL /* no tCon exists yet */ , 13 /* wct */ );
 
+	smb_buffer->Mid = GetNextMid(ses->server);
 	pSMB->req_no_secext.AndXCommand = 0xFF;
 	pSMB->req_no_secext.MaxBufferSize = cpu_to_le16(ses->server->maxBuf);
 	pSMB->req_no_secext.MaxMpxCount = cpu_to_le16(ses->server->maxReq);
@@ -2132,6 +2133,8 @@ CIFSSpnegoSessSetup(unsigned int xid, struct cifsSesInfo *ses,
 	/* send SMBsessionSetup here */
 	header_assemble(smb_buffer, SMB_COM_SESSION_SETUP_ANDX,
 			NULL /* no tCon exists yet */ , 12 /* wct */ );
+
+	smb_buffer->Mid = GetNextMid(ses->server);
 	pSMB->req.hdr.Flags2 |= SMBFLG2_EXT_SEC;
 	pSMB->req.AndXCommand = 0xFF;
 	pSMB->req.MaxBufferSize = cpu_to_le16(ses->server->maxBuf);
@@ -2398,6 +2401,8 @@ CIFSNTLMSSPNegotiateSessSetup(unsigned int xid,
 	/* send SMBsessionSetup here */
 	header_assemble(smb_buffer, SMB_COM_SESSION_SETUP_ANDX,
 			NULL /* no tCon exists yet */ , 12 /* wct */ );
+
+	smb_buffer->Mid = GetNextMid(ses->server);
 	pSMB->req.hdr.Flags2 |= SMBFLG2_EXT_SEC;
 	pSMB->req.hdr.Flags |= (SMBFLG_CASELESS | SMBFLG_CANONICAL_PATH_FORMAT);
 
@@ -2740,6 +2745,8 @@ CIFSNTLMSSPAuthSessSetup(unsigned int xid, struct cifsSesInfo *ses,
 	/* send SMBsessionSetup here */
 	header_assemble(smb_buffer, SMB_COM_SESSION_SETUP_ANDX,
 			NULL /* no tCon exists yet */ , 12 /* wct */ );
+
+	smb_buffer->Mid = GetNextMid(ses->server);
 	pSMB->req.hdr.Flags |= (SMBFLG_CASELESS | SMBFLG_CANONICAL_PATH_FORMAT);
 	pSMB->req.hdr.Flags2 |= SMBFLG2_EXT_SEC;
 	pSMB->req.AndXCommand = 0xFF;
@@ -3111,6 +3118,8 @@ CIFSTCon(unsigned int xid, struct cifsSesInfo *ses,
 
 	header_assemble(smb_buffer, SMB_COM_TREE_CONNECT_ANDX,
 			NULL /*no tid */ , 4 /*wct */ );
+
+	smb_buffer->Mid = GetNextMid(ses->server);
 	smb_buffer->Uid = ses->Suid;
 	pSMB = (TCONX_REQ *) smb_buffer;
 	pSMBr = (TCONX_RSP *) smb_buffer_response;

fs/cifs/misc.c

@@ -34,8 +34,6 @@ extern mempool_t *cifs_sm_req_poolp;
 extern mempool_t *cifs_req_poolp;
 extern struct task_struct * oplockThread;
 
-static __u16 GlobalMid;		/* multiplex id - rotating counter */
-
 /* The xid serves as a useful identifier for each incoming vfs request, 
    in a similar way to the mid which is useful to track each sent smb, 
    and CurrentXid can also provide a running counter (although it 
@@ -51,6 +49,8 @@ _GetXid(void)
 	GlobalTotalActiveXid++;
 	if (GlobalTotalActiveXid > GlobalMaxActiveXid)
 		GlobalMaxActiveXid = GlobalTotalActiveXid;	/* keep high water mark for number of simultaneous vfs ops in our filesystem */
+	if(GlobalTotalActiveXid > 65000)
+		cFYI(1,("warning: more than 65000 requests active"));
 	xid = GlobalCurrentXid++;
 	spin_unlock(&GlobalMid_Lock);
 	return xid;
@@ -218,6 +218,76 @@ cifs_small_buf_release(void *buf_to_free)
 	return;
 }
 
+/* 
+	Find a free multiplex id (SMB mid). Otherwise there could be
+	mid collisions which might cause problems, demultiplexing the
+	wrong response to this request. Multiplex ids could collide if
+	one of a series requests takes much longer than the others, or
+	if a very large number of long lived requests (byte range
+	locks or FindNotify requests) are pending.  No more than
+	64K-1 requests can be outstanding at one time.  If no 
+	mids are available, return zero.  A future optimization
+	could make the combination of mids and uid the key we use
+	to demultiplex on (rather than mid alone).  
+	In addition to the above check, the cifs demultiplex
+	code already used the command code as a secondary
+	check of the frame and if signing is negotiated the
+	response would be discarded if the mid were the same
+	but the signature was wrong.  Since the mid is not put in the
+	pending queue until later (when it is about to be dispatched)
+	we do have to limit the number of outstanding requests 
+	to somewhat less than 64K-1 although it is hard to imagine
+	so many threads being in the vfs at one time.
+*/
+__u16 GetNextMid(struct TCP_Server_Info *server)
+{
+	__u16 mid = 0;
+	__u16 last_mid;
+	int   collision;  
+
+	if(server == NULL)
+		return mid;
+
+	spin_lock(&GlobalMid_Lock);
+	last_mid = server->CurrentMid; /* we do not want to loop forever */
+	server->CurrentMid++;
+	/* This nested loop looks more expensive than it is.
+	In practice the list of pending requests is short, 
+	fewer than 50, and the mids are likely to be unique
+	on the first pass through the loop unless some request
+	takes longer than the 64 thousand requests before it
+	(and it would also have to have been a request that
+	 did not time out) */
+	while(server->CurrentMid != last_mid) {
+		struct list_head *tmp;
+		struct mid_q_entry *mid_entry;
+
+		collision = 0;
+		if(server->CurrentMid == 0)
+			server->CurrentMid++;
+
+		list_for_each(tmp, &server->pending_mid_q) {
+			mid_entry = list_entry(tmp, struct mid_q_entry, qhead);
+
+			if ((mid_entry->mid == server->CurrentMid) &&
+			    (mid_entry->midState == MID_REQUEST_SUBMITTED)) {
+				/* This mid is in use, try a different one */
+				collision = 1;
+				break;
+			}
+		}
+		if(collision == 0) {
+			mid = server->CurrentMid;
+			break;
+		}
+		server->CurrentMid++;
+	}
+	spin_unlock(&GlobalMid_Lock);
+	return mid;
+}
+
+/* NB: MID can not be set if treeCon not passed in, in that
+   case it is responsbility of caller to set the mid */
 void
 header_assemble(struct smb_hdr *buffer, char smb_command /* command */ ,
 		const struct cifsTconInfo *treeCon, int word_count
@@ -233,7 +303,8 @@ header_assemble(struct smb_hdr *buffer, char smb_command /* command */ ,
 	    (2 * word_count) + sizeof (struct smb_hdr) -
 	    4 /*  RFC 1001 length field does not count */  +
 	    2 /* for bcc field itself */ ;
-	/* Note that this is the only network field that has to be converted to big endian and it is done just before we send it */
+	/* Note that this is the only network field that has to be converted
+	   to big endian and it is done just before we send it */
 
 	buffer->Protocol[0] = 0xFF;
 	buffer->Protocol[1] = 'S';
@@ -245,8 +316,6 @@ header_assemble(struct smb_hdr *buffer, char smb_command /* command */ ,
 	buffer->Pid = cpu_to_le16((__u16)current->tgid);
 	buffer->PidHigh = cpu_to_le16((__u16)(current->tgid >> 16));
 	spin_lock(&GlobalMid_Lock);
-	GlobalMid++;
-	buffer->Mid = GlobalMid;
 	spin_unlock(&GlobalMid_Lock);
 	if (treeCon) {
 		buffer->Tid = treeCon->tid;
@@ -256,8 +325,9 @@ header_assemble(struct smb_hdr *buffer, char smb_command /* command */ ,
 			if (treeCon->ses->capabilities & CAP_STATUS32) {
 				buffer->Flags2 |= SMBFLG2_ERR_STATUS;
 			}
-
-			buffer->Uid = treeCon->ses->Suid;	/* always in LE format */
+			/* Uid is not converted */
+			buffer->Uid = treeCon->ses->Suid;
+			buffer->Mid = GetNextMid(treeCon->ses->server);
 			if(multiuser_mount != 0) {
 		/* For the multiuser case, there are few obvious technically  */
 		/* possible mechanisms to match the local linux user (uid)    */