| From | Greg Kroah-Hartman <> | Subject | [PATCH 4.19 048/205] ovl: check whiteout in ovl_create_over_whiteout() | Date | Mon, 19 Nov 2018 17:25:55 +0100 |
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4.19-stable review patch. If anyone has any objections, please let me know.
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From: Miklos Szeredi <mszeredi@redhat.com>
commit 5e1275808630ea3b2c97c776f40e475017535f72 upstream.
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 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
--- fs/overlayfs/dir.c | 4 ++++ 1 file changed, 4 insertions(+)
--- a/fs/overlayfs/dir.c +++ b/fs/overlayfs/dir.c @@ -463,6 +463,10 @@ static int ovl_create_over_whiteout(stru 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))
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