From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from aserp2120.oracle.com ([141.146.126.78]:38768 "EHLO aserp2120.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1760459AbeAISxD (ORCPT ); Tue, 9 Jan 2018 13:53:03 -0500 Date: Tue, 9 Jan 2018 10:47:29 -0800 From: "Darrick J. Wong" Subject: [PATCH v2] xfs: harden directory integrity checks some more Message-ID: <20180109184729.GF5602@magnolia> References: <20180109071336.GD5602@magnolia> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180109071336.GD5602@magnolia> Sender: linux-xfs-owner@vger.kernel.org List-ID: List-Id: xfs To: xfs Cc: Brian Foster From: Darrick J. Wong If a malicious filesystem image contains a block+ format directory wherein the directory inode's core.mode is set such that S_ISDIR(core.mode) == 0, and if there are subdirectories of the corrupted directory, an attempt to traverse up the directory tree will crash the kernel in __xfs_dir3_data_check. Running the online scrub's parent checks will tend to do this. The crash occurs because the directory inode's d_ops get set to xfs_dir[23]_nondir_ops (it's not a directory) but the parent pointer scrubber's indiscriminate call to xfs_readdir proceeds past the ASSERT if we have non fatal asserts configured. Fix the null pointer dereference crash in __xfs_dir3_data_check by looking for S_ISDIR or wrong d_ops; and teach the parent scrubber to bail out if it is fed a non-directory "parent". Signed-off-by: Darrick J. Wong --- v2: check for wrong d_ops, not individual function pointers --- fs/xfs/libxfs/xfs_dir2_data.c | 8 ++++++++ fs/xfs/scrub/parent.c | 2 +- 2 files changed, 9 insertions(+), 1 deletion(-) diff --git a/fs/xfs/libxfs/xfs_dir2_data.c b/fs/xfs/libxfs/xfs_dir2_data.c index 3237812..853d9ab 100644 --- a/fs/xfs/libxfs/xfs_dir2_data.c +++ b/fs/xfs/libxfs/xfs_dir2_data.c @@ -73,6 +73,14 @@ __xfs_dir3_data_check( */ ops = xfs_dir_get_ops(mp, dp); + /* + * If this isn't a directory, or we don't get handed the dir ops, + * something is seriously wrong. Bail out. + */ + if ((dp && !S_ISDIR(VFS_I(dp)->i_mode)) || + ops != xfs_dir_get_ops(mp, NULL)) + return __this_address; + hdr = bp->b_addr; p = (char *)ops->data_entry_p(hdr); diff --git a/fs/xfs/scrub/parent.c b/fs/xfs/scrub/parent.c index dd704fd..0d38514 100644 --- a/fs/xfs/scrub/parent.c +++ b/fs/xfs/scrub/parent.c @@ -171,7 +171,7 @@ xfs_scrub_parent_validate( error = xfs_iget(mp, sc->tp, dnum, 0, 0, &dp); if (!xfs_scrub_fblock_xref_process_error(sc, XFS_DATA_FORK, 0, &error)) goto out; - if (dp == sc->ip) { + if (dp == sc->ip || !S_ISDIR(VFS_I(dp)->i_mode)) { xfs_scrub_fblock_set_corrupt(sc, XFS_DATA_FORK, 0); goto out_rele; }