linux-cve-announce - CVE-2022-49706: zonefs: fix zonefs_iomap

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Message-ID: <2025022630-CVE-2022-49706-eed8@gregkh>
Date: Wed, 26 Feb 2025 03:24:29 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: CVE-2022-49706: zonefs: fix zonefs_iomap_begin() for reads

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

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

zonefs: fix zonefs_iomap_begin() for reads

If a readahead is issued to a sequential zone file with an offset
exactly equal to the current file size, the iomap type is set to
IOMAP_UNWRITTEN, which will prevent an IO, but the iomap length is
calculated as 0. This causes a WARN_ON() in iomap_iter():

[17309.548939] WARNING: CPU: 3 PID: 2137 at fs/iomap/iter.c:34 iomap_iter+0x9cf/0xe80
[...]
[17309.650907] RIP: 0010:iomap_iter+0x9cf/0xe80
[...]
[17309.754560] Call Trace:
[17309.757078]  <TASK>
[17309.759240]  ? lock_is_held_type+0xd8/0x130
[17309.763531]  iomap_readahead+0x1a8/0x870
[17309.767550]  ? iomap_read_folio+0x4c0/0x4c0
[17309.771817]  ? lockdep_hardirqs_on_prepare+0x400/0x400
[17309.778848]  ? lock_release+0x370/0x750
[17309.784462]  ? folio_add_lru+0x217/0x3f0
[17309.790220]  ? reacquire_held_locks+0x4e0/0x4e0
[17309.796543]  read_pages+0x17d/0xb60
[17309.801854]  ? folio_add_lru+0x238/0x3f0
[17309.807573]  ? readahead_expand+0x5f0/0x5f0
[17309.813554]  ? policy_node+0xb5/0x140
[17309.819018]  page_cache_ra_unbounded+0x27d/0x450
[17309.825439]  filemap_get_pages+0x500/0x1450
[17309.831444]  ? filemap_add_folio+0x140/0x140
[17309.837519]  ? lock_is_held_type+0xd8/0x130
[17309.843509]  filemap_read+0x28c/0x9f0
[17309.848953]  ? zonefs_file_read_iter+0x1ea/0x4d0 [zonefs]
[17309.856162]  ? trace_contention_end+0xd6/0x130
[17309.862416]  ? __mutex_lock+0x221/0x1480
[17309.868151]  ? zonefs_file_read_iter+0x166/0x4d0 [zonefs]
[17309.875364]  ? filemap_get_pages+0x1450/0x1450
[17309.881647]  ? __mutex_unlock_slowpath+0x15e/0x620
[17309.888248]  ? wait_for_completion_io_timeout+0x20/0x20
[17309.895231]  ? lock_is_held_type+0xd8/0x130
[17309.901115]  ? lock_is_held_type+0xd8/0x130
[17309.906934]  zonefs_file_read_iter+0x356/0x4d0 [zonefs]
[17309.913750]  new_sync_read+0x2d8/0x520
[17309.919035]  ? __x64_sys_lseek+0x1d0/0x1d0

Furthermore, this causes iomap_readahead() to loop forever as
iomap_readahead_iter() always returns 0, making no progress.

Fix this by treating reads after the file size as access to holes,
setting the iomap type to IOMAP_HOLE, the iomap addr to IOMAP_NULL_ADDR
and using the length argument as is for the iomap length. To simplify
the code with this change, zonefs_iomap_begin() is split into the read
variant, zonefs_read_iomap_begin() and zonefs_read_iomap_ops, and the
write variant, zonefs_write_iomap_begin() and zonefs_write_iomap_ops.

The Linux kernel CVE team has assigned CVE-2022-49706 to this issue.


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

	Issue introduced in 5.6 with commit 8dcc1a9d90c10fa4143e5c17821082e5e60e46a1 and fixed in 5.10.125 with commit 355be6131164c5bacf2e810763835aecb6e01fcb
	Issue introduced in 5.6 with commit 8dcc1a9d90c10fa4143e5c17821082e5e60e46a1 and fixed in 5.15.50 with commit c2f71b9bb398e2e573bdc2574149f42b45efe410
	Issue introduced in 5.6 with commit 8dcc1a9d90c10fa4143e5c17821082e5e60e46a1 and fixed in 5.18.7 with commit 3a7f05f104347b407e865c10be2675cd833a4e48
	Issue introduced in 5.6 with commit 8dcc1a9d90c10fa4143e5c17821082e5e60e46a1 and fixed in 5.19 with commit c1c1204c0d0c1dccc1310b9277fb2bd8b663d8fe

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-2022-49706
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/zonefs/super.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/355be6131164c5bacf2e810763835aecb6e01fcb
	https://git.kernel.org/stable/c/c2f71b9bb398e2e573bdc2574149f42b45efe410
	https://git.kernel.org/stable/c/3a7f05f104347b407e865c10be2675cd833a4e48
	https://git.kernel.org/stable/c/c1c1204c0d0c1dccc1310b9277fb2bd8b663d8fe