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Message-ID: <2025091643-CVE-2023-53317-c945@gregkh>
Date: Tue, 16 Sep 2025 18:12:02 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2023-53317: ext4: fix WARNING in mb_find_extent

From: Greg Kroah-Hartman <gregkh@...nel.org>

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

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

ext4: fix WARNING in mb_find_extent

Syzbot found the following issue:

EXT4-fs: Warning: mounting with data=journal disables delayed allocation, dioread_nolock, O_DIRECT and fast_commit support!
EXT4-fs (loop0): orphan cleanup on readonly fs
------------[ cut here ]------------
WARNING: CPU: 1 PID: 5067 at fs/ext4/mballoc.c:1869 mb_find_extent+0x8a1/0xe30
Modules linked in:
CPU: 1 PID: 5067 Comm: syz-executor307 Not tainted 6.2.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/26/2022
RIP: 0010:mb_find_extent+0x8a1/0xe30 fs/ext4/mballoc.c:1869
RSP: 0018:ffffc90003c9e098 EFLAGS: 00010293
RAX: ffffffff82405731 RBX: 0000000000000041 RCX: ffff8880783457c0
RDX: 0000000000000000 RSI: 0000000000000041 RDI: 0000000000000040
RBP: 0000000000000040 R08: ffffffff82405723 R09: ffffed10053c9402
R10: ffffed10053c9402 R11: 1ffff110053c9401 R12: 0000000000000000
R13: ffffc90003c9e538 R14: dffffc0000000000 R15: ffffc90003c9e2cc
FS:  0000555556665300(0000) GS:ffff8880b9900000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000056312f6796f8 CR3: 0000000022437000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 ext4_mb_complex_scan_group+0x353/0x1100 fs/ext4/mballoc.c:2307
 ext4_mb_regular_allocator+0x1533/0x3860 fs/ext4/mballoc.c:2735
 ext4_mb_new_blocks+0xddf/0x3db0 fs/ext4/mballoc.c:5605
 ext4_ext_map_blocks+0x1868/0x6880 fs/ext4/extents.c:4286
 ext4_map_blocks+0xa49/0x1cc0 fs/ext4/inode.c:651
 ext4_getblk+0x1b9/0x770 fs/ext4/inode.c:864
 ext4_bread+0x2a/0x170 fs/ext4/inode.c:920
 ext4_quota_write+0x225/0x570 fs/ext4/super.c:7105
 write_blk fs/quota/quota_tree.c:64 [inline]
 get_free_dqblk+0x34a/0x6d0 fs/quota/quota_tree.c:130
 do_insert_tree+0x26b/0x1aa0 fs/quota/quota_tree.c:340
 do_insert_tree+0x722/0x1aa0 fs/quota/quota_tree.c:375
 do_insert_tree+0x722/0x1aa0 fs/quota/quota_tree.c:375
 do_insert_tree+0x722/0x1aa0 fs/quota/quota_tree.c:375
 dq_insert_tree fs/quota/quota_tree.c:401 [inline]
 qtree_write_dquot+0x3b6/0x530 fs/quota/quota_tree.c:420
 v2_write_dquot+0x11b/0x190 fs/quota/quota_v2.c:358
 dquot_acquire+0x348/0x670 fs/quota/dquot.c:444
 ext4_acquire_dquot+0x2dc/0x400 fs/ext4/super.c:6740
 dqget+0x999/0xdc0 fs/quota/dquot.c:914
 __dquot_initialize+0x3d0/0xcf0 fs/quota/dquot.c:1492
 ext4_process_orphan+0x57/0x2d0 fs/ext4/orphan.c:329
 ext4_orphan_cleanup+0xb60/0x1340 fs/ext4/orphan.c:474
 __ext4_fill_super fs/ext4/super.c:5516 [inline]
 ext4_fill_super+0x81cd/0x8700 fs/ext4/super.c:5644
 get_tree_bdev+0x400/0x620 fs/super.c:1282
 vfs_get_tree+0x88/0x270 fs/super.c:1489
 do_new_mount+0x289/0xad0 fs/namespace.c:3145
 do_mount fs/namespace.c:3488 [inline]
 __do_sys_mount fs/namespace.c:3697 [inline]
 __se_sys_mount+0x2d3/0x3c0 fs/namespace.c:3674
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

Add some debug information:
mb_find_extent: mb_find_extent block=41, order=0 needed=64 next=0 ex=0/41/1@...5929054 64 64 7
block_bitmap: ff 3f 0c 00 fc 01 00 00 d2 3d 00 00 00 00 00 00 ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff

Acctually, blocks per group is 64, but block bitmap indicate at least has
128 blocks. Now, ext4_validate_block_bitmap() didn't check invalid block's
bitmap if set.
To resolve above issue, add check like fsck "Padding at end of block bitmap is
not set".

The Linux kernel CVE team has assigned CVE-2023-53317 to this issue.


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

	Fixed in 4.19.283 with commit 775b00ba23f6f916fe2ac60c5ff7fd0fe4f28d0d
	Fixed in 5.4.243 with commit 1b90fbc7590124c57a2e590de7fd07eba26606f1
	Fixed in 5.10.180 with commit 5d356d902e9d5b1aaaaf2326d365340fa8a90c1b
	Fixed in 5.15.112 with commit d55e76e11592a1d18a179c7fd34ca1b52632beb3
	Fixed in 6.1.29 with commit dba62fa84a8eac44a53a2862de8a40e5bdfa0ae3
	Fixed in 6.2.16 with commit e4d503c956a744cb59e509ca5f134cfad423c7a3
	Fixed in 6.3.3 with commit dd45e536f47a82e0a405f9a4b6c7ceb367171ee9
	Fixed in 6.4 with commit fa08a7b61dff8a4df11ff1e84abfc214b487caf7

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-2023-53317
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/ext4/balloc.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/775b00ba23f6f916fe2ac60c5ff7fd0fe4f28d0d
	https://git.kernel.org/stable/c/1b90fbc7590124c57a2e590de7fd07eba26606f1
	https://git.kernel.org/stable/c/5d356d902e9d5b1aaaaf2326d365340fa8a90c1b
	https://git.kernel.org/stable/c/d55e76e11592a1d18a179c7fd34ca1b52632beb3
	https://git.kernel.org/stable/c/dba62fa84a8eac44a53a2862de8a40e5bdfa0ae3
	https://git.kernel.org/stable/c/e4d503c956a744cb59e509ca5f134cfad423c7a3
	https://git.kernel.org/stable/c/dd45e536f47a82e0a405f9a4b6c7ceb367171ee9
	https://git.kernel.org/stable/c/fa08a7b61dff8a4df11ff1e84abfc214b487caf7

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