fs/cifs: make share unaccessible at root level mountable

[ Upstream commit a6b5058fafdf508904bbf16c29b24042cef3c496 ]

if, when mounting //HOST/share/sub/dir/foo we can query /sub/dir/foo but
not any of the path components above:

- store the /sub/dir/foo prefix in the cifs super_block info
- in the superblock, set root dentry to the subpath dentry (instead of
  the share root)
- set a flag in the superblock to remember it
- use prefixpath when building path from a dentry

fixes bso#8950

Signed-off-by: Aurelien Aptel <aaptel@suse.com>
CC: Stable <stable@vger.kernel.org>
Reviewed-by: Pavel Shilovsky <pshilovsky@samba.org>
Signed-off-by: Steve French <smfrench@gmail.com>
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>

diff --git a/fs/cifs/cifs_fs_sb.h b/fs/cifs/cifs_fs_sb.h
index 3182273..1418daa 100644 (file)
--- a/fs/cifs/cifs_fs_sb.h
+++ b/fs/cifs/cifs_fs_sb.h
@@ -46,6 +46,9 @@
 #define CIFS_MOUNT_CIFS_BACKUPUID 0x200000 /* backup intent bit for a user */
 #define CIFS_MOUNT_CIFS_BACKUPGID 0x400000 /* backup intent bit for a group */
 #define CIFS_MOUNT_MAP_SFM_CHR 0x800000 /* SFM/MAC mapping for illegal chars */
+#define CIFS_MOUNT_USE_PREFIX_PATH 0x1000000 /* make subpath with unaccessible
+                                             * root mountable
+                                             */
 
 struct cifs_sb_info {
        struct rb_root tlink_tree;
@@ -67,5 +70,6 @@ struct cifs_sb_info {
        struct backing_dev_info bdi;
        struct delayed_work prune_tlinks;
        struct rcu_head rcu;
+       char *prepath;
 };
 #endif                         /* _CIFS_FS_SB_H */

diff --git a/fs/cifs/cifsfs.c b/fs/cifs/cifsfs.c
index fe24e22..9f205a6 100644 (file)
--- a/fs/cifs/cifsfs.c
+++ b/fs/cifs/cifsfs.c
@@ -679,6 +679,14 @@ cifs_do_mount(struct file_system_type *fs_type,
                goto out_cifs_sb;
        }
 
+       if (volume_info->prepath) {
+               cifs_sb->prepath = kstrdup(volume_info->prepath, GFP_KERNEL);
+               if (cifs_sb->prepath == NULL) {
+                       root = ERR_PTR(-ENOMEM);
+                       goto out_cifs_sb;
+               }
+       }
+
        cifs_setup_cifs_sb(volume_info, cifs_sb);
 
        rc = cifs_mount(cifs_sb, volume_info);
@@ -717,7 +725,11 @@ cifs_do_mount(struct file_system_type *fs_type,
                sb->s_flags |= MS_ACTIVE;
        }
 
-       root = cifs_get_root(volume_info, sb);
+       if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_USE_PREFIX_PATH)
+               root = dget(sb->s_root);
+       else
+               root = cifs_get_root(volume_info, sb);
+
        if (IS_ERR(root))
                goto out_super;
 

diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
index 17998d1..cd9d50e 100644 (file)
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -3436,6 +3436,44 @@ cifs_get_volume_info(char *mount_data, const char *devname)
        return volume_info;
 }
 
+static int
+cifs_are_all_path_components_accessible(struct TCP_Server_Info *server,
+                                       unsigned int xid,
+                                       struct cifs_tcon *tcon,
+                                       struct cifs_sb_info *cifs_sb,
+                                       char *full_path)
+{
+       int rc;
+       char *s;
+       char sep, tmp;
+
+       sep = CIFS_DIR_SEP(cifs_sb);
+       s = full_path;
+
+       rc = server->ops->is_path_accessible(xid, tcon, cifs_sb, "");
+       while (rc == 0) {
+               /* skip separators */
+               while (*s == sep)
+                       s++;
+               if (!*s)
+                       break;
+               /* next separator */
+               while (*s && *s != sep)
+                       s++;
+
+               /*
+                * temporarily null-terminate the path at the end of
+                * the current component
+                */
+               tmp = *s;
+               *s = 0;
+               rc = server->ops->is_path_accessible(xid, tcon, cifs_sb,
+                                                    full_path);
+               *s = tmp;
+       }
+       return rc;
+}
+
 int
 cifs_mount(struct cifs_sb_info *cifs_sb, struct smb_vol *volume_info)
 {
@@ -3562,6 +3600,16 @@ remote_path_check:
                        kfree(full_path);
                        goto mount_fail_check;
                }
+
+               rc = cifs_are_all_path_components_accessible(server,
+                                                            xid, tcon, cifs_sb,
+                                                            full_path);
+               if (rc != 0) {
+                       cifs_dbg(VFS, "cannot query dirs between root and final path, "
+                                "enabling CIFS_MOUNT_USE_PREFIX_PATH\n");
+                       cifs_sb->mnt_cifs_flags |= CIFS_MOUNT_USE_PREFIX_PATH;
+                       rc = 0;
+               }
                kfree(full_path);
        }
 
@@ -3831,6 +3879,7 @@ cifs_umount(struct cifs_sb_info *cifs_sb)
 
        bdi_destroy(&cifs_sb->bdi);
        kfree(cifs_sb->mountdata);
+       kfree(cifs_sb->prepath);
        call_rcu(&cifs_sb->rcu, delayed_free);
 }
 

diff --git a/fs/cifs/dir.c b/fs/cifs/dir.c
index 5089e42..26a3b38 100644 (file)
--- a/fs/cifs/dir.c
+++ b/fs/cifs/dir.c
@@ -84,6 +84,7 @@ build_path_from_dentry(struct dentry *direntry)
        struct dentry *temp;
        int namelen;
        int dfsplen;
+       int pplen = 0;
        char *full_path;
        char dirsep;
        struct cifs_sb_info *cifs_sb = CIFS_SB(direntry->d_sb);
@@ -95,8 +96,12 @@ build_path_from_dentry(struct dentry *direntry)
                dfsplen = strnlen(tcon->treeName, MAX_TREE_SIZE + 1);
        else
                dfsplen = 0;
+
+       if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_USE_PREFIX_PATH)
+               pplen = cifs_sb->prepath ? strlen(cifs_sb->prepath) + 1 : 0;
+
 cifs_bp_rename_retry:
-       namelen = dfsplen;
+       namelen = dfsplen + pplen;
        seq = read_seqbegin(&rename_lock);
        rcu_read_lock();
        for (temp = direntry; !IS_ROOT(temp);) {
@@ -137,7 +142,7 @@ cifs_bp_rename_retry:
                }
        }
        rcu_read_unlock();
-       if (namelen != dfsplen || read_seqretry(&rename_lock, seq)) {
+       if (namelen != dfsplen + pplen || read_seqretry(&rename_lock, seq)) {
                cifs_dbg(FYI, "did not end path lookup where expected. namelen=%ddfsplen=%d\n",
                         namelen, dfsplen);
                /* presumably this is only possible if racing with a rename
@@ -153,6 +158,17 @@ cifs_bp_rename_retry:
           those safely to '/' if any are found in the middle of the prepath */
        /* BB test paths to Windows with '/' in the midst of prepath */
 
+       if (pplen) {
+               int i;
+
+               cifs_dbg(FYI, "using cifs_sb prepath <%s>\n", cifs_sb->prepath);
+               memcpy(full_path+dfsplen+1, cifs_sb->prepath, pplen-1);
+               full_path[dfsplen] = '\\';
+               for (i = 0; i < pplen-1; i++)
+                       if (full_path[dfsplen+1+i] == '/')
+                               full_path[dfsplen+1+i] = CIFS_DIR_SEP(cifs_sb);
+       }
+
        if (dfsplen) {
                strncpy(full_path, tcon->treeName, dfsplen);
                if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_POSIX_PATHS) {

diff --git a/fs/cifs/inode.c b/fs/cifs/inode.c
index 6b66dd5..9fb3bc2 100644 (file)
--- a/fs/cifs/inode.c
+++ b/fs/cifs/inode.c
@@ -982,10 +982,26 @@ struct inode *cifs_root_iget(struct super_block *sb)
        struct inode *inode = NULL;
        long rc;
        struct cifs_tcon *tcon = cifs_sb_master_tcon(cifs_sb);
+       char *path = NULL;
+       int len;
+
+       if ((cifs_sb->mnt_cifs_flags & CIFS_MOUNT_USE_PREFIX_PATH)
+           && cifs_sb->prepath) {
+               len = strlen(cifs_sb->prepath);
+               path = kzalloc(len + 2 /* leading sep + null */, GFP_KERNEL);
+               if (path == NULL)
+                       return ERR_PTR(-ENOMEM);
+               path[0] = '/';
+               memcpy(path+1, cifs_sb->prepath, len);
+       } else {
+               path = kstrdup("", GFP_KERNEL);
+               if (path == NULL)
+                       return ERR_PTR(-ENOMEM);
+       }
 
        xid = get_xid();
        if (tcon->unix_ext) {
-               rc = cifs_get_inode_info_unix(&inode, "", sb, xid);
+               rc = cifs_get_inode_info_unix(&inode, path, sb, xid);
                /* some servers mistakenly claim POSIX support */
                if (rc != -EOPNOTSUPP)
                        goto iget_no_retry;
@@ -993,7 +1009,8 @@ struct inode *cifs_root_iget(struct super_block *sb)
                tcon->unix_ext = false;
        }
 
-       rc = cifs_get_inode_info(&inode, "", NULL, sb, xid, NULL);
+       convert_delimiter(path, CIFS_DIR_SEP(cifs_sb));
+       rc = cifs_get_inode_info(&inode, path, NULL, sb, xid, NULL);
 
 iget_no_retry:
        if (!inode) {
@@ -1022,6 +1039,7 @@ iget_no_retry:
        }
 
 out:
+       kfree(path);
        /* can not call macro free_xid here since in a void func
         * TODO: This is no longer true
         */