製品・ソフトウェアに関する情報
Linux の Linux Kernel における NULL ポインタデリファレンスに関する脆弱性
Title Linux の Linux Kernel における NULL ポインタデリファレンスに関する脆弱性
Summary

Linux の Linux Kernel には、NULL ポインタデリファレンスに関する脆弱性が存在します。

Possible impacts サービス運用妨害 (DoS) 状態にされる可能性があります。 
Solution

ベンダより正式な対策が公開されています。ベンダ情報を参照して適切な対策を実施してください。

Publication Date Jan. 16, 2023, midnight
Registration Date Sept. 13, 2024, 9:33 a.m.
Last Update Sept. 13, 2024, 9:33 a.m.
CVSS3.0 : 警告
Score 4.7
Vector CVSS:3.0/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H
Affected System
Linux
Linux Kernel 5.10.99 以上 5.10.165 未満
Linux Kernel 5.15.22 以上 5.15.90 未満
Linux Kernel 5.16.8 より大きい 5.17 未満
Linux Kernel 5.17 以上 6.1.8 未満
Linux Kernel 5.4.178 以上 5.4.230 未満
Linux Kernel 6.2
CVE (情報セキュリティ 共通脆弱性識別子)
CWE (共通脆弱性タイプ一覧)
ベンダー情報
Change Log
No Changed Details Date of change
1 [2024年09月12日]   掲載 Sept. 12, 2024, 9:54 a.m.

NVD Vulnerability Information
CVE-2023-52896
Summary

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

btrfs: fix race between quota rescan and disable leading to NULL pointer deref

If we have one task trying to start the quota rescan worker while another
one is trying to disable quotas, we can end up hitting a race that results
in the quota rescan worker doing a NULL pointer dereference. The steps for
this are the following:

1) Quotas are enabled;

2) Task A calls the quota rescan ioctl and enters btrfs_qgroup_rescan().
It calls qgroup_rescan_init() which returns 0 (success) and then joins a
transaction and commits it;

3) Task B calls the quota disable ioctl and enters btrfs_quota_disable().
It clears the bit BTRFS_FS_QUOTA_ENABLED from fs_info->flags and calls
btrfs_qgroup_wait_for_completion(), which returns immediately since the
rescan worker is not yet running.
Then it starts a transaction and locks fs_info->qgroup_ioctl_lock;

4) Task A queues the rescan worker, by calling btrfs_queue_work();

5) The rescan worker starts, and calls rescan_should_stop() at the start
of its while loop, which results in 0 iterations of the loop, since
the flag BTRFS_FS_QUOTA_ENABLED was cleared from fs_info->flags by
task B at step 3);

6) Task B sets fs_info->quota_root to NULL;

7) The rescan worker tries to start a transaction and uses
fs_info->quota_root as the root argument for btrfs_start_transaction().
This results in a NULL pointer dereference down the call chain of
btrfs_start_transaction(). The stack trace is something like the one
reported in Link tag below:

general protection fault, probably for non-canonical address 0xdffffc0000000041: 0000 [#1] PREEMPT SMP KASAN
KASAN: null-ptr-deref in range [0x0000000000000208-0x000000000000020f]
CPU: 1 PID: 34 Comm: kworker/u4:2 Not tainted 6.1.0-syzkaller-13872-gb6bb9676f216 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/26/2022
Workqueue: btrfs-qgroup-rescan btrfs_work_helper
RIP: 0010:start_transaction+0x48/0x10f0 fs/btrfs/transaction.c:564
Code: 48 89 fb 48 (...)
RSP: 0018:ffffc90000ab7ab0 EFLAGS: 00010206
RAX: 0000000000000041 RBX: 0000000000000208 RCX: ffff88801779ba80
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000000
RBP: dffffc0000000000 R08: 0000000000000001 R09: fffff52000156f5d
R10: fffff52000156f5d R11: 1ffff92000156f5c R12: 0000000000000000
R13: 0000000000000001 R14: 0000000000000001 R15: 0000000000000003
FS: 0000000000000000(0000) GS:ffff8880b9900000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f2bea75b718 CR3: 000000001d0cc000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
btrfs_qgroup_rescan_worker+0x3bb/0x6a0 fs/btrfs/qgroup.c:3402
btrfs_work_helper+0x312/0x850 fs/btrfs/async-thread.c:280
process_one_work+0x877/0xdb0 kernel/workqueue.c:2289
worker_thread+0xb14/0x1330 kernel/workqueue.c:2436
kthread+0x266/0x300 kernel/kthread.c:376
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:308
</TASK>
Modules linked in:

So fix this by having the rescan worker function not attempt to start a
transaction if it didn't do any rescan work.

Publication Date Aug. 21, 2024, 4:15 p.m.
Registration Date Aug. 26, 2024, 4:58 p.m.
Last Update Sept. 12, 2024, 1:37 a.m.
Affected software configurations
Configuration1 or higher or less more than less than
cpe:2.3:o:linux:linux_kernel:6.2:rc1:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:6.2:rc2:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:6.2:rc3:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:6.2:rc4:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* 5.17 6.1.8
cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* 5.10.99 5.10.165
cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* 5.4.178 5.4.230
cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* 5.15.22 5.15.90
cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* 5.16.8 5.17
Related information, measures and tools
Common Vulnerabilities List