2 files changed, 38 insertions, 13 deletions

diff --git a/fs/cifs/CHANGES b/fs/cifs/CHANGES
index 5ab6bcce880a..080703a15f44 100644
--- a/fs/cifs/CHANGES
+++ b/fs/cifs/CHANGES
@@ -4,7 +4,8 @@ Add "forcemandatorylock" mount option to allow user to use mandatory
 rather than posix (advisory) byte range locks, even though server would
 support posix byte range locks.  Fix query of root inode when prefixpath
 specified and user does not have access to query information about the
-top of the share.
+top of the share.  Fix problem in 2.6.28 resolving DFS paths to
+Samba servers (worked to Windows).
 
 Version 1.55
 ------------
diff --git a/fs/cifs/cifs_dfs_ref.c b/fs/cifs/cifs_dfs_ref.c
index e1c18362ba46..85c0a74d034d 100644
--- a/fs/cifs/cifs_dfs_ref.c
+++ b/fs/cifs/cifs_dfs_ref.c
@@ -122,7 +122,7 @@ static char *compose_mount_options(const char *sb_mountdata,
                                    char **devname)
 {
         int rc;
-        char *mountdata;
+        char *mountdata = NULL;
         int md_len;
         char *tkn_e;
         char *srvIP = NULL;
@@ -136,10 +136,9 @@ static char *compose_mount_options(const char *sb_mountdata,
         *devname = cifs_get_share_name(ref->node_name);
         rc = dns_resolve_server_name_to_ip(*devname, &srvIP);
         if (rc != 0) {
-                cERROR(1, ("%s: Failed to resolve server part of %s to IP",
-                          __func__, *devname));
-                mountdata = ERR_PTR(rc);
-                goto compose_mount_options_out;
+                cERROR(1, ("%s: Failed to resolve server part of %s to IP: %d",
+                          __func__, *devname, rc));;
+                goto compose_mount_options_err;
         }
         /* md_len = strlen(...) + 12 for 'sep+prefixpath='
          * assuming that we have 'unc=' and 'ip=' in
@@ -149,8 +148,8 @@ static char *compose_mount_options(const char *sb_mountdata,
                 strlen(ref->node_name) + 12;
         mountdata = kzalloc(md_len+1, GFP_KERNEL);
         if (mountdata == NULL) {
-                mountdata = ERR_PTR(-ENOMEM);
-                goto compose_mount_options_out;
+                rc = -ENOMEM;
+                goto compose_mount_options_err;
         }
 
         /* copy all options except of unc,ip,prefixpath */
@@ -197,18 +196,32 @@ static char *compose_mount_options(const char *sb_mountdata,
 
         /* find & copy prefixpath */
         tkn_e = strchr(ref->node_name + 2, '\\');
-        if (tkn_e == NULL) /* invalid unc, missing share name*/
-                goto compose_mount_options_out;
+        if (tkn_e == NULL) {
+                /* invalid unc, missing share name*/
+                rc = -EINVAL;
+                goto compose_mount_options_err;
+        }
 
+        /*
+         * this function gives us a path with a double backslash prefix. We
+         * require a single backslash for DFS. Temporarily increment fullpath
+         * to put it in the proper form and decrement before freeing it.
+         */
         fullpath = build_path_from_dentry(dentry);
+        if (!fullpath) {
+                rc = -ENOMEM;
+                goto compose_mount_options_err;
+        }
+        ++fullpath;
         tkn_e = strchr(tkn_e + 1, '\\');
-        if (tkn_e || strlen(fullpath) - (ref->path_consumed)) {
+        if (tkn_e || (strlen(fullpath) - ref->path_consumed)) {
                 strncat(mountdata, &sep, 1);
                 strcat(mountdata, "prefixpath=");
                 if (tkn_e)
                         strcat(mountdata, tkn_e + 1);
-                strcat(mountdata, fullpath + (ref->path_consumed));
+                strcat(mountdata, fullpath + ref->path_consumed);
         }
+        --fullpath;
         kfree(fullpath);
 
         /*cFYI(1,("%s: parent mountdata: %s", __func__,sb_mountdata));*/
@@ -217,6 +230,11 @@ static char *compose_mount_options(const char *sb_mountdata,
 compose_mount_options_out:
         kfree(srvIP);
         return mountdata;
+
+compose_mount_options_err:
+        kfree(mountdata);
+        mountdata = ERR_PTR(rc);
+        goto compose_mount_options_out;
 }
 
 
@@ -309,13 +327,19 @@ cifs_dfs_follow_mountpoint(struct dentry *dentry, struct nameidata *nd)
                 goto out_err;
         }
 
+        /*
+         * The MSDFS spec states that paths in DFS referral requests and
+         * responses must be prefixed by a single '\' character instead of
+         * the double backslashes usually used in the UNC. This function
+         * gives us the latter, so we must adjust the result.
+         */
         full_path = build_path_from_dentry(dentry);
         if (full_path == NULL) {
                 rc = -ENOMEM;
                 goto out_err;
         }
 
-        rc = get_dfs_path(xid, ses , full_path, cifs_sb->local_nls,
+        rc = get_dfs_path(xid, ses , full_path + 1, cifs_sb->local_nls,
                 &num_referrals, &referrals,
                 cifs_sb->mnt_cifs_flags & CIFS_MOUNT_MAP_SPECIAL_CHR);