1 files changed, 87 insertions, 4 deletions

diff --git a/fs/cifs/sess.c b/fs/cifs/sess.c
index 5f22de7b79a..5c68b4282be 100644
--- a/fs/cifs/sess.c
+++ b/fs/cifs/sess.c
@@ -34,15 +34,99 @@
 extern void SMBNTencrypt(unsigned char *passwd, unsigned char *c8,
                          unsigned char *p24);
 
+/* Checks if this is the first smb session to be reconnected after
+   the socket has been reestablished (so we know whether to use vc 0).
+   Called while holding the cifs_tcp_ses_lock, so do not block */
+static bool is_first_ses_reconnect(struct cifsSesInfo *ses)
+{
+        struct list_head *tmp;
+        struct cifsSesInfo *tmp_ses;
+
+        list_for_each(tmp, &ses->server->smb_ses_list) {
+                tmp_ses = list_entry(tmp, struct cifsSesInfo,
+                                     smb_ses_list);
+                if (tmp_ses->need_reconnect == false)
+                        return false;
+        }
+        /* could not find a session that was already connected,
+           this must be the first one we are reconnecting */
+        return true;
+}
+
+/*
+ *      vc number 0 is treated specially by some servers, and should be the
+ *      first one we request.  After that we can use vcnumbers up to maxvcs,
+ *      one for each smb session (some Windows versions set maxvcs incorrectly
+ *      so maxvc=1 can be ignored).  If we have too many vcs, we can reuse
+ *      any vc but zero (some servers reset the connection on vcnum zero)
+ *
+ */
+static __le16 get_next_vcnum(struct cifsSesInfo *ses)
+{
+        __u16 vcnum = 0;
+        struct list_head *tmp;
+        struct cifsSesInfo *tmp_ses;
+        __u16 max_vcs = ses->server->max_vcs;
+        __u16 i;
+        int free_vc_found = 0;
+
+        /* Quoting the MS-SMB specification: "Windows-based SMB servers set this
+        field to one but do not enforce this limit, which allows an SMB client
+        to establish more virtual circuits than allowed by this value ... but
+        other server implementations can enforce this limit." */
+        if (max_vcs < 2)
+                max_vcs = 0xFFFF;
+
+        write_lock(&cifs_tcp_ses_lock);
+        if ((ses->need_reconnect) && is_first_ses_reconnect(ses))
+                        goto get_vc_num_exit;  /* vcnum will be zero */
+        for (i = ses->server->srv_count - 1; i < max_vcs; i++) {
+                if (i == 0) /* this is the only connection, use vc 0 */
+                        break;
+
+                free_vc_found = 1;
+
+                list_for_each(tmp, &ses->server->smb_ses_list) {
+                        tmp_ses = list_entry(tmp, struct cifsSesInfo,
+                                             smb_ses_list);
+                        if (tmp_ses->vcnum == i) {
+                                free_vc_found = 0;
+                                break; /* found duplicate, try next vcnum */
+                        }
+                }
+                if (free_vc_found)
+                        break; /* we found a vcnumber that will work - use it */
+        }
+
+        if (i == 0)
+                vcnum = 0; /* for most common case, ie if one smb session, use
+                              vc zero.  Also for case when no free vcnum, zero
+                              is safest to send (some clients only send zero) */
+        else if (free_vc_found == 0)
+                vcnum = 1;  /* we can not reuse vc=0 safely, since some servers
+                                reset all uids on that, but 1 is ok. */
+        else
+                vcnum = i;
+        ses->vcnum = vcnum;
+get_vc_num_exit:
+        write_unlock(&cifs_tcp_ses_lock);
+
+        return le16_to_cpu(vcnum);
+}
+
 static __u32 cifs_ssetup_hdr(struct cifsSesInfo *ses, SESSION_SETUP_ANDX *pSMB)
 {
         __u32 capabilities = 0;
 
         /* init fields common to all four types of SessSetup */
-        /* note that header is initialized to zero in header_assemble */
+        /* Note that offsets for first seven fields in req struct are same  */
+        /*      in CIFS Specs so does not matter which of 3 forms of struct */
+        /*      that we use in next few lines                               */
+        /* Note that header is initialized to zero in header_assemble */
         pSMB->req.AndXCommand = 0xFF;
         pSMB->req.MaxBufferSize = cpu_to_le16(ses->server->maxBuf);
         pSMB->req.MaxMpxCount = cpu_to_le16(ses->server->maxReq);
+        pSMB->req.VcNumber = get_next_vcnum(ses);
 
         /* Now no need to set SMBFLG_CASELESS or obsolete CANONICAL PATH */
 
@@ -71,7 +155,6 @@ static __u32 cifs_ssetup_hdr(struct cifsSesInfo *ses, SESSION_SETUP_ANDX *pSMB)
         if (ses->capabilities & CAP_UNIX)
                 capabilities |= CAP_UNIX;
 
-        /* BB check whether to init vcnum BB */
         return capabilities;
 }
 
@@ -228,7 +311,7 @@ static int decode_unicode_ssetup(char **pbcc_area, int bleft,
 
         kfree(ses->serverOS);
         /* UTF-8 string will not grow more than four times as big as UCS-16 */
-        ses->serverOS = kzalloc(4 * len, GFP_KERNEL);
+        ses->serverOS = kzalloc((4 * len) + 2 /* trailing null */, GFP_KERNEL);
         if (ses->serverOS != NULL)
                 cifs_strfromUCS_le(ses->serverOS, (__le16 *)data, len, nls_cp);
         data += 2 * (len + 1);
@@ -241,7 +324,7 @@ static int decode_unicode_ssetup(char **pbcc_area, int bleft,
                 return rc;
 
         kfree(ses->serverNOS);
-        ses->serverNOS = kzalloc(4 * len, GFP_KERNEL); /* BB this is wrong length FIXME BB */
+        ses->serverNOS = kzalloc((4 * len) + 2 /* trailing null */, GFP_KERNEL);
         if (ses->serverNOS != NULL) {
                 cifs_strfromUCS_le(ses->serverNOS, (__le16 *)data, len,
                                    nls_cp);