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

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)
Cc: <stable@vger.kernel.org> #v2.6.29+
Signed-off-by: Jeff Mahoney <jeffm@suse.com>
Signed-off-by: Chris Mason <clm@fb.com>

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index b2a2da5..7fd939b 100644 (file)
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -1634,6 +1634,9 @@ static noinline int btrfs_ioctl_snap_create_transid(struct file *file,
        int namelen;
        int ret = 0;
 
+       if (!S_ISDIR(file_inode(file)->i_mode))
+               return -ENOTDIR;
+
        ret = mnt_want_write_file(file);
        if (ret)
                goto out;
@@ -1691,6 +1694,9 @@ static noinline int btrfs_ioctl_snap_create(struct file *file,
        struct btrfs_ioctl_vol_args *vol_args;
        int ret;
 
+       if (!S_ISDIR(file_inode(file)->i_mode))
+               return -ENOTDIR;
+
        vol_args = memdup_user(arg, sizeof(*vol_args));
        if (IS_ERR(vol_args))
                return PTR_ERR(vol_args);
@@ -1714,6 +1720,9 @@ static noinline int btrfs_ioctl_snap_create_v2(struct file *file,
        bool readonly = false;
        struct btrfs_qgroup_inherit *inherit = NULL;
 
+       if (!S_ISDIR(file_inode(file)->i_mode))
+               return -ENOTDIR;
+
        vol_args = memdup_user(arg, sizeof(*vol_args));
        if (IS_ERR(vol_args))
                return PTR_ERR(vol_args);
@@ -2357,6 +2366,9 @@ 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);