CVE-2022-49450: linux kernel Null Dereference — Fix

Description

In the Linux kernel, the following vulnerability has been resolved: rxrpc: Fix listen() setting the bar too high for the prealloc rings AF_RXRPC's listen() handler lets you set the backlog up to 32 (if you bump up the sysctl), but whilst the preallocation circular buffers have 32 slots in them, one of them has to be a dead slot because we're using CIRC_CNT(). This means that listen(rxrpc_sock, 32) will cause an oops when the socket is closed because rxrpc_service_prealloc_one() allocated one too many calls and rxrpc_discard_prealloc() won't then be able to get rid of them because it'll think the ring is empty. rxrpc_release_calls_on_socket() then tries to abort them, but oopses because call->peer isn't yet set. Fix this by setting the maximum backlog to RXRPC_BACKLOG_MAX - 1 to match the ring capacity. BUG: kernel NULL pointer dereference, address: 0000000000000086 ... RIP: 0010:rxrpc_send_abort_packet+0x73/0x240 [rxrpc] Call Trace: <TASK> ? __wake_up_common_lock+0x7a/0x90 ? rxrpc_notify_socket+0x8e/0x140 [rxrpc] ? rxrpc_abort_call+0x4c/0x60 [rxrpc] rxrpc_release_calls_on_socket+0x107/0x1a0 [rxrpc] rxrpc_release+0xc9/0x1c0 [rxrpc] __sock_release+0x37/0xa0 sock_close+0x11/0x20 __fput+0x89/0x240 task_work_run+0x59/0x90 do_exit+0x319/0xaa0

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CVSS v3.1 Score

5.5

MEDIUM

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

Weakness Type (CWE)

CWE-476 CWE-476

Affected Products

Vendor	Product	Versions
linux	linux_kernel	4.9 — 4.9.318
linux	linux_kernel	4.10 — 4.14.283
linux	linux_kernel	4.15 — 4.19.247
linux	linux_kernel	4.20 — 5.4.198
linux	linux_kernel	5.5 — 5.10.121
linux	linux_kernel	5.11 — 5.15.46
linux	linux_kernel	5.16 — 5.17.14
linux	linux_kernel	5.18 — 5.18.3

References

Advisories & Patches

Frequently Asked Questions

What is CVE-2022-49450? +

In the Linux kernel, the following vulnerability has been resolved: rxrpc: Fix listen() setting the bar too high for the prealloc rings AF_RXRPC's listen() handler lets you set the backlog up to 32 (if you bump up the sysctl), but whilst the preallocation circular buffers have 32 slots in them, one of them has to be a dead slot because we're using CIRC_CNT(). This means that listen(rxrpc_sock, 32) will cause an oops when the socket is closed because rxrpc_service_prealloc_one() allocated one too many calls and rxrpc_discard_prealloc() won't then be able to get rid of them because it'll think the ring is empty. rxrpc_release_calls_on_socket() then tries to abort them, but oopses because call->peer isn't yet set. Fix this by setting the maximum backlog to RXRPC_BACKLOG_MAX - 1 to match the ring capacity. BUG: kernel NULL pointer dereference, address: 0000000000000086 ... RIP: 0010:rxrpc_send_abort_packet+0x73/0x240 [rxrpc] Call Trace: <TASK> ? __wake_up_common_lock+0x7a/0x90 ? rxrpc_notify_socket+0x8e/0x140 [rxrpc] ? rxrpc_abort_call+0x4c/0x60 [rxrpc] rxrpc_release_calls_on_socket+0x107/0x1a0 [rxrpc] rxrpc_release+0xc9/0x1c0 [rxrpc] __sock_release+0x37/0xa0 sock_close+0x11/0x20 __fput+0x89/0x240 task_work_run+0x59/0x90 do_exit+0x319/0xaa0 It has a CVSS v3.1 base score of 5.5 (MEDIUM).

How severe is CVE-2022-49450? +

CVE-2022-49450 has a CVSS v3.1 score of 5.5 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance.

What products are affected by CVE-2022-49450? +

CVE-2022-49450 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-2022-49450? +

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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