From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 957F3EB64D9 for ; Thu, 29 Jun 2023 16:35:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231245AbjF2Qfj (ORCPT ); Thu, 29 Jun 2023 12:35:39 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45482 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230401AbjF2Qfi (ORCPT ); Thu, 29 Jun 2023 12:35:38 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2CFAC30EE for ; Thu, 29 Jun 2023 09:35:37 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id B6F7061595 for ; Thu, 29 Jun 2023 16:35:36 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 179EEC433C0; Thu, 29 Jun 2023 16:35:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1688056536; bh=KwfQsPQOxgFTfbsCEs8MWkvvWUbqKvKGdyMxNWscj4E=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=jCxoPywC2wTbyE4bq0AjAZHiY0t9fIrGTM2lrSWsTnwDfXEauTrsgis2i3ctoBW0I BxmplYYecmlRoO2SNqk7ZRkU5xnz2cJTI/jHuT5wF8Y5JMEek9XpDRlgEzBnzOdb9w VOb+GvX4Qjs2e6M/ma4zar4QftO01NFotKgn/YTrSv2tA5At2wiPL0JJxwzaZTGnrj u6usZaoONy7TFMleSRlJPzhWhbI3A0Lel1NAPK61DM/MVgrSDyCdshmYxyhb89oOD9 zD/RCnVpkaMzzfbIauMTd5554qbY6p/vWanPvn5uSuZqg6JjZdGseYa0VVWuVeK45O 4OlQpiGZX78hg== Date: Thu, 29 Jun 2023 09:35:35 -0700 From: "Darrick J. Wong" To: Dave Chinner Cc: linux-xfs@vger.kernel.org Subject: Re: [PATCH 7/8 V2] xfs: AGF length has never been bounds checked Message-ID: <20230629163535.GG11441@frogsfrogsfrogs> References: <20230627224412.2242198-1-david@fromorbit.com> <20230627224412.2242198-8-david@fromorbit.com> <20230628175211.GX11441@frogsfrogsfrogs> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-xfs@vger.kernel.org On Thu, Jun 29, 2023 at 12:09:25PM +1000, Dave Chinner wrote: > From: Dave Chinner > > The AGF verifier does not check that the AGF length field is within > known good bounds. This has never been checked by runtime kernel > code (i.e. the lack of verification goes back to 1993) yet we assume > in many places that it is correct and verify other metdata against > it. > > Add length verification to the AGF verifier. The length of the AGF > must be equal to the size of the AG specified in the superblock, > unless it is the last AG in the filesystem. In that case, it must be > less than or equal to sb->sb_agblocks and greater than > XFS_MIN_AG_BLOCKS, which is the smallest AG a growfs operation will > allow to exist. > > This requires a bit of rework of the verifier function. We want to > verify metadata before we use it to verify other metadata. Hence > we need to verify the AGF sequence numbers before using them to > verify the length of the AGF. Then we can verify the AGF length > before we verify AGFL fields. Then we can verifier other fields that > are bounds limited by the AGF length. > > And, finally, by calculating agf_length only once into a local > variable, we can collapse repeated "if (xfs_has_foo() &&" > conditionaly checks into single checks. This makes the code much > easier to follow as all the checks for a given feature are obviously > in the same place. > > Signed-off-by: Dave Chinner > Reviewed-by: Christoph Hellwig > Reviewed-by: Darrick J. Wong Still looks good to me. New question: Do we need to validate agi_length in the AGI verifier too? --D > --- > > Version 2: > - growfs will write the new AGFs before the superblock has been > updated, so we have to skip the new runt AGF seqno check otherwise > it will fail. > > fs/xfs/libxfs/xfs_alloc.c | 92 +++++++++++++++++++++++++++++------------------ > 1 file changed, 57 insertions(+), 35 deletions(-) > > diff --git a/fs/xfs/libxfs/xfs_alloc.c b/fs/xfs/libxfs/xfs_alloc.c > index 1e72b91daff6..fe7d5ea47b90 100644 > --- a/fs/xfs/libxfs/xfs_alloc.c > +++ b/fs/xfs/libxfs/xfs_alloc.c > @@ -2974,6 +2974,7 @@ xfs_agf_verify( > { > struct xfs_mount *mp = bp->b_mount; > struct xfs_agf *agf = bp->b_addr; > + uint32_t agf_length = be32_to_cpu(agf->agf_length); > > if (xfs_has_crc(mp)) { > if (!uuid_equal(&agf->agf_uuid, &mp->m_sb.sb_meta_uuid)) > @@ -2985,18 +2986,49 @@ xfs_agf_verify( > if (!xfs_verify_magic(bp, agf->agf_magicnum)) > return __this_address; > > - if (!(XFS_AGF_GOOD_VERSION(be32_to_cpu(agf->agf_versionnum)) && > - be32_to_cpu(agf->agf_freeblks) <= be32_to_cpu(agf->agf_length) && > - be32_to_cpu(agf->agf_flfirst) < xfs_agfl_size(mp) && > - be32_to_cpu(agf->agf_fllast) < xfs_agfl_size(mp) && > - be32_to_cpu(agf->agf_flcount) <= xfs_agfl_size(mp))) > + if (!XFS_AGF_GOOD_VERSION(be32_to_cpu(agf->agf_versionnum))) > return __this_address; > > - if (be32_to_cpu(agf->agf_length) > mp->m_sb.sb_dblocks) > + /* > + * Both agf_seqno and agf_length need to validated before anything else > + * block number related in the AGF or AGFL can be checked. > + * > + * During growfs operations, the perag is not fully initialised, > + * so we can't use it for any useful checking. growfs ensures we can't > + * use it by using uncached buffers that don't have the perag attached > + * so we can detect and avoid this problem. > + */ > + if (bp->b_pag && be32_to_cpu(agf->agf_seqno) != bp->b_pag->pag_agno) > + return __this_address; > + > + /* > + * Only the last AGF in the filesytsem is allowed to be shorter > + * than the AG size recorded in the superblock. > + */ > + if (agf_length != mp->m_sb.sb_agblocks) { > + /* > + * During growfs, the new last AGF can get here before we > + * have updated the superblock. Give it a pass on the seqno > + * check. > + */ > + if (bp->b_pag && > + be32_to_cpu(agf->agf_seqno) != mp->m_sb.sb_agcount - 1) > + return __this_address; > + if (agf_length < XFS_MIN_AG_BLOCKS) > + return __this_address; > + if (agf_length > mp->m_sb.sb_agblocks) > + return __this_address; > + } > + > + if (be32_to_cpu(agf->agf_flfirst) >= xfs_agfl_size(mp)) > + return __this_address; > + if (be32_to_cpu(agf->agf_fllast) >= xfs_agfl_size(mp)) > + return __this_address; > + if (be32_to_cpu(agf->agf_flcount) > xfs_agfl_size(mp)) > return __this_address; > > if (be32_to_cpu(agf->agf_freeblks) < be32_to_cpu(agf->agf_longest) || > - be32_to_cpu(agf->agf_freeblks) > be32_to_cpu(agf->agf_length)) > + be32_to_cpu(agf->agf_freeblks) > agf_length) > return __this_address; > > if (be32_to_cpu(agf->agf_levels[XFS_BTNUM_BNO]) < 1 || > @@ -3007,38 +3039,28 @@ xfs_agf_verify( > mp->m_alloc_maxlevels) > return __this_address; > > - if (xfs_has_rmapbt(mp) && > - (be32_to_cpu(agf->agf_levels[XFS_BTNUM_RMAP]) < 1 || > - be32_to_cpu(agf->agf_levels[XFS_BTNUM_RMAP]) > > - mp->m_rmap_maxlevels)) > - return __this_address; > - > - if (xfs_has_rmapbt(mp) && > - be32_to_cpu(agf->agf_rmap_blocks) > be32_to_cpu(agf->agf_length)) > - return __this_address; > - > - /* > - * during growfs operations, the perag is not fully initialised, > - * so we can't use it for any useful checking. growfs ensures we can't > - * use it by using uncached buffers that don't have the perag attached > - * so we can detect and avoid this problem. > - */ > - if (bp->b_pag && be32_to_cpu(agf->agf_seqno) != bp->b_pag->pag_agno) > - return __this_address; > - > if (xfs_has_lazysbcount(mp) && > - be32_to_cpu(agf->agf_btreeblks) > be32_to_cpu(agf->agf_length)) > + be32_to_cpu(agf->agf_btreeblks) > agf_length) > return __this_address; > > - if (xfs_has_reflink(mp) && > - be32_to_cpu(agf->agf_refcount_blocks) > > - be32_to_cpu(agf->agf_length)) > - return __this_address; > + if (xfs_has_rmapbt(mp)) { > + if (be32_to_cpu(agf->agf_rmap_blocks) > agf_length) > + return __this_address; > > - if (xfs_has_reflink(mp) && > - (be32_to_cpu(agf->agf_refcount_level) < 1 || > - be32_to_cpu(agf->agf_refcount_level) > mp->m_refc_maxlevels)) > - return __this_address; > + if (be32_to_cpu(agf->agf_levels[XFS_BTNUM_RMAP]) < 1 || > + be32_to_cpu(agf->agf_levels[XFS_BTNUM_RMAP]) > > + mp->m_rmap_maxlevels) > + return __this_address; > + } > + > + if (xfs_has_reflink(mp)) { > + if (be32_to_cpu(agf->agf_refcount_blocks) > agf_length) > + return __this_address; > + > + if (be32_to_cpu(agf->agf_refcount_level) < 1 || > + be32_to_cpu(agf->agf_refcount_level) > mp->m_refc_maxlevels) > + return __this_address; > + } > > return NULL; > }