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authorMiklos Szeredi <mszeredi@redhat.com>2018-10-31 12:15:23 +0100
committerMiklos Szeredi <mszeredi@redhat.com>2018-10-31 12:15:23 +0100
commit5e1275808630ea3b2c97c776f40e475017535f72 (patch)
tree0a7d5c43ac0b662ad2822627a6f2dbc371c21530
parent14fa085640a7eb55431eec8a0273bbf0c463ce46 (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.c4
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))