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| author | Miklos Szeredi <mszeredi@redhat.com> | 2018-10-31 12:15:23 +0100 |
|---|---|---|
| committer | Miklos Szeredi <mszeredi@redhat.com> | 2018-10-31 12:15:23 +0100 |
| commit | 5e1275808630ea3b2c97c776f40e475017535f72 (patch) | |
| tree | 0a7d5c43ac0b662ad2822627a6f2dbc371c21530 | |
| parent | 14fa085640a7eb55431eec8a0273bbf0c463ce46 (diff) | |
| download | linux-5e1275808630ea3b2c97c776f40e475017535f72.tar.bz2 | |
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, if (IS_ERR(upper)) goto out_unlock; + err = -ESTALE; + if (d_is_negative(upper) || !IS_WHITEOUT(d_inode(upper))) + goto out_dput; + newdentry = ovl_create_temp(workdir, cattr); err = PTR_ERR(newdentry); if (IS_ERR(newdentry)) |