linux-kernel - [PATCH 5.4 10/57] xfs: trim IO to found COW extent limit

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20201005142110.303121498@linuxfoundation.org>
Date:   Mon,  5 Oct 2020 17:26:22 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Eric Sandeen <sandeen@...hat.com>,
        "Darrick J. Wong" <darrick.wong@...cle.com>,
        Christoph Hellwig <hch@....de>, Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.4 10/57] xfs: trim IO to found COW extent limit

From: Eric Sandeen <sandeen@...deen.net>

A bug existed in the XFS reflink code between v5.1 and v5.5 in which
the mapping for a COW IO was not trimmed to the mapping of the COW
extent that was found.  This resulted in a too-short copy, and
corruption of other files which shared the original extent.

(This happened only when extent size hints were set, which bypasses
delalloc and led to this code path.)

This was (inadvertently) fixed upstream with

36adcbace24e "xfs: fill out the srcmap in iomap_begin"

and related patches which moved lots of this functionality to
the iomap subsystem.

Hence, this is a -stable only patch, targeted to fix this
corruption vector without other major code changes.

Fixes: 78f0cc9d55cb ("xfs: don't use delalloc extents for COW on files with extsize hints")
Cc: <stable@...r.kernel.org> # 5.4.x
Signed-off-by: Eric Sandeen <sandeen@...hat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@...cle.com>
Reviewed-by: Christoph Hellwig <hch@....de>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 fs/xfs/xfs_iomap.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c
index f780e223b1185..239c9548b1568 100644
--- a/fs/xfs/xfs_iomap.c
+++ b/fs/xfs/xfs_iomap.c
@@ -1002,9 +1002,15 @@ xfs_file_iomap_begin(
 		 * I/O, which must be block aligned, we need to report the
 		 * newly allocated address.  If the data fork has a hole, copy
 		 * the COW fork mapping to avoid allocating to the data fork.
+		 *
+		 * Otherwise, ensure that the imap range does not extend past
+		 * the range allocated/found in cmap.
 		 */
 		if (directio || imap.br_startblock == HOLESTARTBLOCK)
 			imap = cmap;
+		else
+			xfs_trim_extent(&imap, cmap.br_startoff,
+					cmap.br_blockcount);
 
 		end_fsb = imap.br_startoff + imap.br_blockcount;
 		length = XFS_FSB_TO_B(mp, end_fsb) - offset;
-- 
2.25.1