cifs: fix composing of mount options for DFS referrals

With the change to ignore the unc= and prefixpath= mount options, there
is no longer any need to add them to the options string when mounting.
By the same token, we now need to build a device name that includes the
prefixpath when mounting.

To make things neater, the delimiters on the devicename are changed
to '/' since that's preferred when mounting anyway.

v2: fix some comments and don't bother looking at whether there is
    a prepath in the ref->node_name when deciding whether to pass
    a prepath to cifs_build_devname.

v3: rebase on top of potential buffer overrun fix for stable

Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>

diff --git a/fs/cifs/cifs_dfs_ref.c b/fs/cifs/cifs_dfs_ref.c
index 8e5a181..58df174 100644 (file)
--- a/fs/cifs/cifs_dfs_ref.c
+++ b/fs/cifs/cifs_dfs_ref.c
@@ -49,58 +49,74 @@ void cifs_dfs_release_automount_timer(void)
 }
 
 /**
- * cifs_get_share_name -       extracts share name from UNC
- * @node_name: pointer to UNC string
+ * cifs_build_devname - build a devicename from a UNC and optional prepath
+ * @nodename:  pointer to UNC string
+ * @prepath:   pointer to prefixpath (or NULL if there isn't one)
  *
- * Extracts sharename form full UNC.
- * i.e. strips from UNC trailing path that is not part of share
- * name and fixup missing '\' in the beginning of DFS node refferal
- * if necessary.
- * Returns pointer to share name on success or ERR_PTR on error.
- * Caller is responsible for freeing returned string.
+ * Build a new cifs devicename after chasing a DFS referral. Allocate a buffer
+ * big enough to hold the final thing. Copy the UNC from the nodename, and
+ * concatenate the prepath onto the end of it if there is one.
+ *
+ * Returns pointer to the built string, or a ERR_PTR. Caller is responsible
+ * for freeing the returned string.
  */
-static char *cifs_get_share_name(const char *node_name)
+static char *
+cifs_build_devname(char *nodename, const char *prepath)
 {
-       int len;
-       char *UNC;
-       char *pSep;
-
-       len = strlen(node_name);
-       UNC = kmalloc(len+2 /*for term null and additional \ if it's missed */,
-                        GFP_KERNEL);
-       if (!UNC)
-               return ERR_PTR(-ENOMEM);
+       size_t pplen;
+       size_t unclen;
+       char *dev;
+       char *pos;
+
+       /* skip over any preceding delimiters */
+       nodename += strspn(nodename, "\\");
+       if (!*nodename)
+               return ERR_PTR(-EINVAL);
 
-       /* get share name and server name */
-       if (node_name[1] != '\\') {
-               UNC[0] = '\\';
-               strncpy(UNC+1, node_name, len);
-               len++;
-               UNC[len] = 0;
-       } else {
-               strncpy(UNC, node_name, len);
-               UNC[len] = 0;
-       }
+       /* get length of UNC and set pos to last char */
+       unclen = strlen(nodename);
+       pos = nodename + unclen - 1;
 
-       /* find server name end */
-       pSep = memchr(UNC+2, '\\', len-2);
-       if (!pSep) {
-               cifs_dbg(VFS, "%s: no server name end in node name: %s\n",
-                        __func__, node_name);
-               kfree(UNC);
-               return ERR_PTR(-EINVAL);
+       /* trim off any trailing delimiters */
+       while (*pos == '\\') {
+               --pos;
+               --unclen;
        }
 
-       /* find sharename end */
-       pSep++;
-       pSep = memchr(UNC+(pSep-UNC), '\\', len-(pSep-UNC));
-       if (pSep) {
-               /* trim path up to sharename end
-                * now we have share name in UNC */
-               *pSep = 0;
+       /* allocate a buffer:
+        * +2 for preceding "//"
+        * +1 for delimiter between UNC and prepath
+        * +1 for trailing NULL
+        */
+       pplen = prepath ? strlen(prepath) : 0;
+       dev = kmalloc(2 + unclen + 1 + pplen + 1, GFP_KERNEL);
+       if (!dev)
+               return ERR_PTR(-ENOMEM);
+
+       pos = dev;
+       /* add the initial "//" */
+       *pos = '/';
+       ++pos;
+       *pos = '/';
+       ++pos;
+
+       /* copy in the UNC portion from referral */
+       memcpy(pos, nodename, unclen);
+       pos += unclen;
+
+       /* copy the prefixpath remainder (if there is one) */
+       if (pplen) {
+               *pos = '/';
+               ++pos;
+               memcpy(pos, prepath, pplen);
+               pos += pplen;
        }
 
-       return UNC;
+       /* NULL terminator */
+       *pos = '\0';
+
+       convert_delimiter(dev, '/');
+       return dev;
 }
 
 
@@ -124,6 +140,7 @@ char *cifs_compose_mount_options(const char *sb_mountdata,
 {
        int rc;
        char *mountdata = NULL;
+       const char *prepath = NULL;
        int md_len;
        char *tkn_e;
        char *srvIP = NULL;
@@ -133,7 +150,10 @@ char *cifs_compose_mount_options(const char *sb_mountdata,
        if (sb_mountdata == NULL)
                return ERR_PTR(-EINVAL);
 
-       *devname = cifs_get_share_name(ref->node_name);
+       if (strlen(fullpath) - ref->path_consumed)
+               prepath = fullpath + ref->path_consumed;
+
+       *devname = cifs_build_devname(ref->node_name, prepath);
        if (IS_ERR(*devname)) {
                rc = PTR_ERR(*devname);
                *devname = NULL;
@@ -147,13 +167,14 @@ char *cifs_compose_mount_options(const char *sb_mountdata,
                goto compose_mount_options_err;
        }
 
-       /* md_len = strlen(...) + 12 for 'sep+prefixpath='
-        * assuming that we have 'unc=' and 'ip=' in
-        * the original sb_mountdata
+       /*
+        * In most cases, we'll be building a shorter string than the original,
+        * but we do have to assume that the address in the ip= option may be
+        * much longer than the original. Add the max length of an address
+        * string to the length of the original string to allow for worst case.
         */
-       md_len = strlen(sb_mountdata) + rc + strlen(ref->node_name) + 12 +
-                       INET6_ADDRSTRLEN;
-       mountdata = kzalloc(md_len+1, GFP_KERNEL);
+       md_len = strlen(sb_mountdata) + INET6_ADDRSTRLEN;
+       mountdata = kzalloc(md_len + 1, GFP_KERNEL);
        if (mountdata == NULL) {
                rc = -ENOMEM;
                goto compose_mount_options_err;
@@ -197,26 +218,6 @@ char *cifs_compose_mount_options(const char *sb_mountdata,
                strncat(mountdata, &sep, 1);
        strcat(mountdata, "ip=");
        strcat(mountdata, srvIP);
-       strncat(mountdata, &sep, 1);
-       strcat(mountdata, "unc=");
-       strcat(mountdata, *devname);
-
-       /* find & copy prefixpath */
-       tkn_e = strchr(ref->node_name + 2, '\\');
-       if (tkn_e == NULL) {
-               /* invalid unc, missing share name*/
-               rc = -EINVAL;
-               goto compose_mount_options_err;
-       }
-
-       tkn_e = strchr(tkn_e + 1, '\\');
-       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);
-       }
 
        /*cifs_dbg(FYI, "%s: parent mountdata: %s\n", __func__, sb_mountdata);*/
        /*cifs_dbg(FYI, "%s: submount mountdata: %s\n", __func__, mountdata );*/

diff --git a/fs/cifs/dns_resolve.c b/fs/cifs/dns_resolve.c
index e7512e4..7ede730 100644 (file)
--- a/fs/cifs/dns_resolve.c
+++ b/fs/cifs/dns_resolve.c
@@ -34,7 +34,7 @@
 
 /**
  * dns_resolve_server_name_to_ip - Resolve UNC server name to ip address.
- * @unc: UNC path specifying the server
+ * @unc: UNC path specifying the server (with '/' as delimiter)
  * @ip_addr: Where to return the IP address.
  *
  * The IP address will be returned in string form, and the caller is
@@ -64,7 +64,7 @@ dns_resolve_server_name_to_ip(const char *unc, char **ip_addr)
        hostname = unc + 2;
 
        /* Search for server name delimiter */
-       sep = memchr(hostname, '\\', len);
+       sep = memchr(hostname, '/', len);
        if (sep)
                len = sep - hostname;
        else