CVE-2021-47369: linux kernel Null Dereference — Fix

Description

In the Linux kernel, the following vulnerability has been resolved: s390/qeth: fix NULL deref in qeth_clear_working_pool_list() When qeth_set_online() calls qeth_clear_working_pool_list() to roll back after an error exit from qeth_hardsetup_card(), we are at risk of accessing card->qdio.in_q before it was allocated by qeth_alloc_qdio_queues() via qeth_mpc_initialize(). qeth_clear_working_pool_list() then dereferences NULL, and by writing to queue->bufs[i].pool_entry scribbles all over the CPU's lowcore. Resulting in a crash when those lowcore areas are used next (eg. on the next machine-check interrupt). Such a scenario would typically happen when the device is first set online and its queues aren't allocated yet. An early IO error or certain misconfigs (eg. mismatched transport mode, bad portno) then cause us to error out from qeth_hardsetup_card() with card->qdio.in_q still being NULL. Fix it by checking the pointer for NULL before accessing it. Note that we also have (rare) paths inside qeth_mpc_initialize() where a configuration change can cause us to free the existing queues, expecting that subsequent code will allocate them again. If we then error out before that re-allocation happens, the same bug occurs. Root-caused-by: Heiko Carstens <[email protected]>

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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	5.7.16 — 5.8
linux	linux_kernel	5.8.2 — 5.10.70
linux	linux_kernel	5.11 — 5.14.9
linux	linux_kernel	All
linux	linux_kernel	All

References

Advisories & Patches

https://git.kernel.org/stable/c/248f064af222a1f97ee02c84a98013dfbccad386 https://git.kernel.org/stable/c/9b00fb12cdc9d8d1c3ffe82a78e74738127803fc https://git.kernel.org/stable/c/db94f89e1dadf693c15c2d60de0c34777cea5779 https://git.kernel.org/stable/c/248f064af222a1f97ee02c84a98013dfbccad386 https://git.kernel.org/stable/c/9b00fb12cdc9d8d1c3ffe82a78e74738127803fc https://git.kernel.org/stable/c/db94f89e1dadf693c15c2d60de0c34777cea5779

Frequently Asked Questions

What is CVE-2021-47369? +

In the Linux kernel, the following vulnerability has been resolved: s390/qeth: fix NULL deref in qeth_clear_working_pool_list() When qeth_set_online() calls qeth_clear_working_pool_list() to roll back after an error exit from qeth_hardsetup_card(), we are at risk of accessing card->qdio.in_q before it was allocated by qeth_alloc_qdio_queues() via qeth_mpc_initialize(). qeth_clear_working_pool_list() then dereferences NULL, and by writing to queue->bufs[i].pool_entry scribbles all over the CPU's lowcore. Resulting in a crash when those lowcore areas are used next (eg. on the next machine-check interrupt). Such a scenario would typically happen when the device is first set online and its queues aren't allocated yet. An early IO error or certain misconfigs (eg. mismatched transport mode, bad portno) then cause us to error out from qeth_hardsetup_card() with card->qdio.in_q still being NULL. Fix it by checking the pointer for NULL before accessing it. Note that we also have (rare) paths inside qeth_mpc_initialize() where a configuration change can cause us to free the existing queues, expecting that subsequent code will allocate them again. If we then error out before that re-allocation happens, the same bug occurs. Root-caused-by: Heiko Carstens <[email protected]> It has a CVSS v3.1 base score of 5.5 (MEDIUM).

How severe is CVE-2021-47369? +

CVE-2021-47369 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-2021-47369? +

CVE-2021-47369 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-2021-47369? +

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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CVE-2021-47369