btrfs: ensure that file descriptor used with subvol ioctls is a dir

commit 325c50e3cebb9208009083e841550f98a863bfa0 upstream.

If the subvol/snapshot create/destroy ioctls are passed a regular file
with execute permissions set, we'll eventually Oops while trying to do
inode->i_op->lookup via lookup_one_len.

This patch ensures that the file descriptor refers to a directory.

Fixes: cb8e70901d (Btrfs: Fix subvolume creation locking rules)
Fixes: 76dda93c6a (Btrfs: add snapshot/subvolume destroy ioctl)
Signed-off-by: Jeff Mahoney <jeffm@suse.com>
Signed-off-by: Chris Mason <clm@fb.com>
[bwh: Backported to 3.2:
 - Open-code file_inode()
 - Adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index eb6a0e6..360072f 100644 (file)
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -1302,6 +1302,9 @@ static noinline int btrfs_ioctl_snap_create_transid(struct file *file,
        int namelen;
        int ret = 0;
 
+       if (!S_ISDIR(file->f_dentry->d_inode->i_mode))
+               return -ENOTDIR;
+
        if (root->fs_info->sb->s_flags & MS_RDONLY)
                return -EROFS;
 
@@ -1350,6 +1353,9 @@ static noinline int btrfs_ioctl_snap_create(struct file *file,
        struct btrfs_ioctl_vol_args *vol_args;
        int ret;
 
+       if (!S_ISDIR(file->f_dentry->d_inode->i_mode))
+               return -ENOTDIR;
+
        vol_args = memdup_user(arg, sizeof(*vol_args));
        if (IS_ERR(vol_args))
                return PTR_ERR(vol_args);
@@ -1372,6 +1378,9 @@ static noinline int btrfs_ioctl_snap_create_v2(struct file *file,
        u64 *ptr = NULL;
        bool readonly = false;
 
+       if (!S_ISDIR(file->f_dentry->d_inode->i_mode))
+               return -ENOTDIR;
+
        vol_args = memdup_user(arg, sizeof(*vol_args));
        if (IS_ERR(vol_args))
                return PTR_ERR(vol_args);
@@ -1848,6 +1857,9 @@ static noinline int btrfs_ioctl_snap_destroy(struct file *file,
        int ret;
        int err = 0;
 
+       if (!S_ISDIR(dir->i_mode))
+               return -ENOTDIR;
+
        vol_args = memdup_user(arg, sizeof(*vol_args));
        if (IS_ERR(vol_args))
                return PTR_ERR(vol_args);