4.7
MEDIUM
CVE-2023-52896
"Btrfs Quota Rescan Null Pointer Dereference"
Description

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.

INFO

Published Date :

Aug. 21, 2024, 7:15 a.m.

Last Modified :

Sept. 11, 2024, 4:37 p.m.

Source :

416baaa9-dc9f-4396-8d5f-8c081fb06d67

Remotely Exploitable :

No

Impact Score :

3.6

Exploitability Score :

1.0
Affected Products

The following products are affected by CVE-2023-52896 vulnerability. Even if cvefeed.io is aware of the exact versions of the products that are affected, the information is not represented in the table below.

ID Vendor Product Action
1 Linux linux_kernel
: Total Affected Vendor : 1 | Products : 1
References to Advisories, Solutions, and Tools

Here, you will find a curated list of external links that provide in-depth information, practical solutions, and valuable tools related to CVE-2023-52896.

URL Resource
https://git.kernel.org/stable/c/1004fc90f0d79a4b7d9e3d432729914f472f9ad1 Patch
https://git.kernel.org/stable/c/3bd43374857103ba3cac751d6d4afa8d83b5d92a Patch
https://git.kernel.org/stable/c/64287cd456a22373053998c1fccf14b651e9cbbd Patch
https://git.kernel.org/stable/c/89ac597e3e807b91e2ebd6a7c36fec7b97290233 Patch
https://git.kernel.org/stable/c/b7adbf9ada3513d2092362c8eac5cddc5b651f5c Patch

We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).

Results are limited to the first 15 repositories due to potential performance issues.

The following list is the news that have been mention CVE-2023-52896 vulnerability anywhere in the article.

The following table lists the changes that have been made to the CVE-2023-52896 vulnerability over time.

Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.

  • Initial Analysis by [email protected]

    Sep. 11, 2024

    Action Type Old Value New Value
    Added CVSS V3.1 NIST AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H
    Changed Reference Type https://git.kernel.org/stable/c/1004fc90f0d79a4b7d9e3d432729914f472f9ad1 No Types Assigned https://git.kernel.org/stable/c/1004fc90f0d79a4b7d9e3d432729914f472f9ad1 Patch
    Changed Reference Type https://git.kernel.org/stable/c/3bd43374857103ba3cac751d6d4afa8d83b5d92a No Types Assigned https://git.kernel.org/stable/c/3bd43374857103ba3cac751d6d4afa8d83b5d92a Patch
    Changed Reference Type https://git.kernel.org/stable/c/64287cd456a22373053998c1fccf14b651e9cbbd No Types Assigned https://git.kernel.org/stable/c/64287cd456a22373053998c1fccf14b651e9cbbd Patch
    Changed Reference Type https://git.kernel.org/stable/c/89ac597e3e807b91e2ebd6a7c36fec7b97290233 No Types Assigned https://git.kernel.org/stable/c/89ac597e3e807b91e2ebd6a7c36fec7b97290233 Patch
    Changed Reference Type https://git.kernel.org/stable/c/b7adbf9ada3513d2092362c8eac5cddc5b651f5c No Types Assigned https://git.kernel.org/stable/c/b7adbf9ada3513d2092362c8eac5cddc5b651f5c Patch
    Added CWE NIST CWE-476
    Added CPE Configuration OR *cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* versions from (including) 5.4.178 up to (excluding) 5.4.230 *cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* versions from (including) 5.10.99 up to (excluding) 5.10.165 *cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* versions from (including) 5.15.22 up to (excluding) 5.15.90 *cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* versions from (excluding) 5.16.8 up to (excluding) 5.17 *cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* versions from (including) 5.17 up to (excluding) 6.1.8 *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:*:*:*:*:*:*
  • CVE Received by 416baaa9-dc9f-4396-8d5f-8c081fb06d67

    Aug. 21, 2024

    Action Type Old Value New Value
    Added Description 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.
    Added Reference kernel.org https://git.kernel.org/stable/c/89ac597e3e807b91e2ebd6a7c36fec7b97290233 [No types assigned]
    Added Reference kernel.org https://git.kernel.org/stable/c/3bd43374857103ba3cac751d6d4afa8d83b5d92a [No types assigned]
    Added Reference kernel.org https://git.kernel.org/stable/c/64287cd456a22373053998c1fccf14b651e9cbbd [No types assigned]
    Added Reference kernel.org https://git.kernel.org/stable/c/1004fc90f0d79a4b7d9e3d432729914f472f9ad1 [No types assigned]
    Added Reference kernel.org https://git.kernel.org/stable/c/b7adbf9ada3513d2092362c8eac5cddc5b651f5c [No types assigned]
EPSS is a daily estimate of the probability of exploitation activity being observed over the next 30 days. Following chart shows the EPSS score history of the vulnerability.
CWE - Common Weakness Enumeration

While CVE identifies specific instances of vulnerabilities, CWE categorizes the common flaws or weaknesses that can lead to vulnerabilities. CVE-2023-52896 is associated with the following CWEs:

Common Attack Pattern Enumeration and Classification (CAPEC)

Common Attack Pattern Enumeration and Classification (CAPEC) stores attack patterns, which are descriptions of the common attributes and approaches employed by adversaries to exploit the CVE-2023-52896 weaknesses.

CVSS31 - Vulnerability Scoring System
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