diff options
author | Miklos Szeredi <mszeredi@redhat.com> | 2018-10-31 07:15:23 -0400 |
---|---|---|
committer | Miklos Szeredi <mszeredi@redhat.com> | 2018-10-31 07:15:23 -0400 |
commit | 5e1275808630ea3b2c97c776f40e475017535f72 (patch) | |
tree | 0a7d5c43ac0b662ad2822627a6f2dbc371c21530 | |
parent | 14fa085640a7eb55431eec8a0273bbf0c463ce46 (diff) |
ovl: check whiteout in ovl_create_over_whiteout()
Kaixuxia repors that it's possible to crash overlayfs by removing the
whiteout on the upper layer before creating a directory over it. This is a
reproducer:
mkdir lower upper work merge
touch lower/file
mount -t overlay overlay -olowerdir=lower,upperdir=upper,workdir=work merge
rm merge/file
ls -al merge/file
rm upper/file
ls -al merge/
mkdir merge/file
Before commencing with a vfs_rename(..., RENAME_EXCHANGE) verify that the
lookup of "upper" is positive and is a whiteout, and return ESTALE
otherwise.
Reported by: kaixuxia <xiakaixu1987@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Fixes: e9be9d5e76e3 ("overlay filesystem")
Cc: <stable@vger.kernel.org> # v3.18
-rw-r--r-- | fs/overlayfs/dir.c | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/fs/overlayfs/dir.c b/fs/overlayfs/dir.c index ce1857fb5434..c6289147c787 100644 --- a/fs/overlayfs/dir.c +++ b/fs/overlayfs/dir.c | |||
@@ -462,6 +462,10 @@ static int ovl_create_over_whiteout(struct dentry *dentry, struct inode *inode, | |||
462 | if (IS_ERR(upper)) | 462 | if (IS_ERR(upper)) |
463 | goto out_unlock; | 463 | goto out_unlock; |
464 | 464 | ||
465 | err = -ESTALE; | ||
466 | if (d_is_negative(upper) || !IS_WHITEOUT(d_inode(upper))) | ||
467 | goto out_dput; | ||
468 | |||
465 | newdentry = ovl_create_temp(workdir, cattr); | 469 | newdentry = ovl_create_temp(workdir, cattr); |
466 | err = PTR_ERR(newdentry); | 470 | err = PTR_ERR(newdentry); |
467 | if (IS_ERR(newdentry)) | 471 | if (IS_ERR(newdentry)) |