CVE-2024-53186: linux kernel Use-After-Free — Fix

Description

In the Linux kernel, the following vulnerability has been resolved: ksmbd: fix use-after-free in SMB request handling A race condition exists between SMB request handling in `ksmbd_conn_handler_loop()` and the freeing of `ksmbd_conn` in the workqueue handler `handle_ksmbd_work()`. This leads to a UAF. - KASAN: slab-use-after-free Read in handle_ksmbd_work - KASAN: slab-use-after-free in rtlock_slowlock_locked This race condition arises as follows: - `ksmbd_conn_handler_loop()` waits for `conn->r_count` to reach zero: `wait_event(conn->r_count_q, atomic_read(&conn->r_count) == 0);` - Meanwhile, `handle_ksmbd_work()` decrements `conn->r_count` using `atomic_dec_return(&conn->r_count)`, and if it reaches zero, calls `ksmbd_conn_free()`, which frees `conn`. - However, after `handle_ksmbd_work()` decrements `conn->r_count`, it may still access `conn->r_count_q` in the following line: `waitqueue_active(&conn->r_count_q)` or `wake_up(&conn->r_count_q)` This results in a UAF, as `conn` has already been freed. The discovery of this UAF can be referenced in the following PR for syzkaller's support for SMB requests.

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CVSS v3.1 Score

7.0

HIGH

CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H

Weakness Type (CWE)

CWE-362 CWE-362

CWE-416 Use After Free

Affected Products

Vendor	Product	Versions
linux	linux_kernel	6.6.55 — 6.6.64
linux	linux_kernel	6.10.14 — 6.11
linux	linux_kernel	6.11.3 — 6.11.11
linux	linux_kernel	6.12 — 6.12.2

References

Advisories & Patches

https://git.kernel.org/stable/c/96261adb998a3b513468b6ce17dbec76be5507d4 https://git.kernel.org/stable/c/9a8c5d89d327ff58e9b2517f8a6afb4181d32c6e https://git.kernel.org/stable/c/a96f9eb7add30ba0fafcfe7b7aca090978196800 https://git.kernel.org/stable/c/f20b77f7897e6aab9ce5527e6016ad2be5d70a33

Frequently Asked Questions

What is CVE-2024-53186? +

In the Linux kernel, the following vulnerability has been resolved: ksmbd: fix use-after-free in SMB request handling A race condition exists between SMB request handling in `ksmbd_conn_handler_loop()` and the freeing of `ksmbd_conn` in the workqueue handler `handle_ksmbd_work()`. This leads to a UAF. - KASAN: slab-use-after-free Read in handle_ksmbd_work - KASAN: slab-use-after-free in rtlock_slowlock_locked This race condition arises as follows: - `ksmbd_conn_handler_loop()` waits for `conn->r_count` to reach zero: `wait_event(conn->r_count_q, atomic_read(&conn->r_count) == 0);` - Meanwhile, `handle_ksmbd_work()` decrements `conn->r_count` using `atomic_dec_return(&conn->r_count)`, and if it reaches zero, calls `ksmbd_conn_free()`, which frees `conn`. - However, after `handle_ksmbd_work()` decrements `conn->r_count`, it may still access `conn->r_count_q` in the following line: `waitqueue_active(&conn->r_count_q)` or `wake_up(&conn->r_count_q)` This results in a UAF, as `conn` has already been freed. The discovery of this UAF can be referenced in the following PR for syzkaller's support for SMB requests. It has a CVSS v3.1 base score of 7.0 (HIGH).

How severe is CVE-2024-53186? +

CVE-2024-53186 has a CVSS v3.1 score of 7.0 out of 10, rated HIGH. This is a high-severity vulnerability that should be prioritized for patching.

What products are affected by CVE-2024-53186? +

CVE-2024-53186 affects products from linux, specifically: linux_kernel. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2024-53186? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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