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

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

6 files changed, 113 insertions, 29 deletions

diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h
index d3773e57acf9..e8287f76484f 100644
--- a/fs/cifs/cifsglob.h
+++ b/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 */
diff --git a/fs/cifs/cifspdu.h b/fs/cifs/cifspdu.h
index 3cef57b7a34f..49cc66825309 100644
--- a/fs/cifs/cifspdu.h
+++ b/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
diff --git a/fs/cifs/cifsproto.h b/fs/cifs/cifsproto.h
index 66eaa6b40373..b9b13e3fe79d 100644
--- a/fs/cifs/cifsproto.h
+++ b/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 *);
diff --git a/fs/cifs/cifssmb.c b/fs/cifs/cifssmb.c
index 1b073546f5d9..930be0927de2 100644
--- a/fs/cifs/cifssmb.c
+++ b/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) {
diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
index 36f78596c81a..9e8256003f73 100644
--- a/fs/cifs/connect.c
+++ b/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;
diff --git a/fs/cifs/misc.c b/fs/cifs/misc.c
index 20ae4153f791..beeff8284169 100644
--- a/fs/cifs/misc.c
+++ b/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)    */