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Subject[PATCH 3.16 315/346] btrfs: ensure that file descriptor used with subvol ioctls is a dir
3.16.39-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Jeff Mahoney <jeffm@suse.com>

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>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
fs/btrfs/ioctl.c | 12 ++++++++++++
1 file changed, 12 insertions(+)

--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -1649,6 +1649,9 @@ static noinline int btrfs_ioctl_snap_cre
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;
@@ -1706,6 +1709,9 @@ static noinline int btrfs_ioctl_snap_cre
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);
@@ -1729,6 +1735,9 @@ static noinline int btrfs_ioctl_snap_cre
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);
@@ -2355,6 +2364,9 @@ static noinline int btrfs_ioctl_snap_des
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);
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