Message-ID: <2024071219-CVE-2024-40943-b7ee@gregkh>
Date: Fri, 12 Jul 2024 14:27:41 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: CVE-2024-40943: ocfs2: fix races between hole punching and AIO+DIO

Description
===========

In the Linux kernel, the following vulnerability has been resolved:

ocfs2: fix races between hole punching and AIO+DIO

After commit "ocfs2: return real error code in ocfs2_dio_wr_get_block",
fstests/generic/300 become from always failed to sometimes failed:

========================================================================
[  473.293420 ] run fstests generic/300

[  475.296983 ] JBD2: Ignoring recovery information on journal
[  475.302473 ] ocfs2: Mounting device (253,1) on (node local, slot 0) with ordered data mode.
[  494.290998 ] OCFS2: ERROR (device dm-1): ocfs2_change_extent_flag: Owner 5668 has an extent at cpos 78723 which can no longer be found
[  494.291609 ] On-disk corruption discovered. Please run fsck.ocfs2 once the filesystem is unmounted.
[  494.292018 ] OCFS2: File system is now read-only.
[  494.292224 ] (kworker/19:11,2628,19):ocfs2_mark_extent_written:5272 ERROR: status = -30
[  494.292602 ] (kworker/19:11,2628,19):ocfs2_dio_end_io_write:2374 ERROR: status = -3
fio: io_u error on file /mnt/scratch/racer: Read-only file system: write offset=460849152, buflen=131072
=========================================================================

In __blockdev_direct_IO, ocfs2_dio_wr_get_block is called to add unwritten
extents to a list.  extents are also inserted into extent tree in
ocfs2_write_begin_nolock.  Then another thread call fallocate to puch a
hole at one of the unwritten extent.  The extent at cpos was removed by
ocfs2_remove_extent().  At end io worker thread, ocfs2_search_extent_list
found there is no such extent at the cpos.

    T1                        T2                T3
                              inode lock
                                ...
                                insert extents
                                ...
                              inode unlock
ocfs2_fallocate
 __ocfs2_change_file_space
  inode lock
  lock ip_alloc_sem
  ocfs2_remove_inode_range inode
   ocfs2_remove_btree_range
    ocfs2_remove_extent
    ^---remove the extent at cpos 78723
  ...
  unlock ip_alloc_sem
  inode unlock
                                       ocfs2_dio_end_io
                                        ocfs2_dio_end_io_write
                                         lock ip_alloc_sem
                                         ocfs2_mark_extent_written
                                          ocfs2_change_extent_flag
                                           ocfs2_search_extent_list
                                           ^---failed to find extent
                                          ...
                                          unlock ip_alloc_sem

In most filesystems, fallocate is not compatible with racing with AIO+DIO,
so fix it by adding to wait for all dio before fallocate/punch_hole like
ext4.

The Linux kernel CVE team has assigned CVE-2024-40943 to this issue.


Affected and fixed versions
===========================

	Issue introduced in 2.6.23 with commit b25801038da5 and fixed in 4.19.317 with commit 3c26b5d21b12
	Issue introduced in 2.6.23 with commit b25801038da5 and fixed in 5.4.279 with commit e8e2db1adac4
	Issue introduced in 2.6.23 with commit b25801038da5 and fixed in 5.10.221 with commit 050ce8af6838
	Issue introduced in 2.6.23 with commit b25801038da5 and fixed in 5.15.162 with commit 38825ff9da91
	Issue introduced in 2.6.23 with commit b25801038da5 and fixed in 6.1.95 with commit ea042dc2bea1
	Issue introduced in 2.6.23 with commit b25801038da5 and fixed in 6.6.35 with commit 3c361f313d69
	Issue introduced in 2.6.23 with commit b25801038da5 and fixed in 6.9.6 with commit 117b9c009b72
	Issue introduced in 2.6.23 with commit b25801038da5 and fixed in 6.10-rc1 with commit 952b023f06a2

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2024-40943
will be updated if fixes are backported, please check that for the most
up to date information about this issue.


Affected files
==============

The file(s) affected by this issue are:
	fs/ocfs2/file.c


Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/3c26b5d21b1239e9c7fd31ba7d9b2d7bdbaa68d9
	https://git.kernel.org/stable/c/e8e2db1adac47970a6a9225f3858e9aa0e86287f
	https://git.kernel.org/stable/c/050ce8af6838c71e872e982b50d3f1bec21da40e
	https://git.kernel.org/stable/c/38825ff9da91d2854dcf6d9ac320a7e641e10f25
	https://git.kernel.org/stable/c/ea042dc2bea19d72e37c298bf65a9c341ef3fff3
	https://git.kernel.org/stable/c/3c361f313d696df72f9bccf058510e9ec737b9b1
	https://git.kernel.org/stable/c/117b9c009b72a6c2ebfd23484354dfee2d9570d2
	https://git.kernel.org/stable/c/952b023f06a24b2ad6ba67304c4c84d45bea2f18

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