CVE-2024-50273: linux kernel — Fix

Description

In the Linux kernel, the following vulnerability has been resolved: btrfs: reinitialize delayed ref list after deleting it from the list At insert_delayed_ref() if we need to update the action of an existing ref to BTRFS_DROP_DELAYED_REF, we delete the ref from its ref head's ref_add_list using list_del(), which leaves the ref's add_list member not reinitialized, as list_del() sets the next and prev members of the list to LIST_POISON1 and LIST_POISON2, respectively. If later we end up calling drop_delayed_ref() against the ref, which can happen during merging or when destroying delayed refs due to a transaction abort, we can trigger a crash since at drop_delayed_ref() we call list_empty() against the ref's add_list, which returns false since the list was not reinitialized after the list_del() and as a consequence we call list_del() again at drop_delayed_ref(). This results in an invalid list access since the next and prev members are set to poison pointers, resulting in a splat if CONFIG_LIST_HARDENED and CONFIG_DEBUG_LIST are set or invalid poison pointer dereferences otherwise. So fix this by deleting from the list with list_del_init() instead.

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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-908 CWE-908

Affected Products

Vendor	Product	Versions
linux	linux_kernel	4.10 — 4.19.324
linux	linux_kernel	4.20 — 5.4.286
linux	linux_kernel	5.5 — 5.10.230
linux	linux_kernel	5.11 — 5.15.172
linux	linux_kernel	5.16 — 6.1.117
linux	linux_kernel	6.2 — 6.6.61
linux	linux_kernel	6.7 — 6.11.8
linux	linux_kernel	All
linux	linux_kernel	All
linux	linux_kernel	All
linux	linux_kernel	All
linux	linux_kernel	All
linux	linux_kernel	All

References

Advisories & Patches

https://git.kernel.org/stable/c/2cb1a73d1d44a1c11b0ee5eeced765dd80ec48e6 https://git.kernel.org/stable/c/2fd0948a483e9cb2d669c7199bc620a21c97673d https://git.kernel.org/stable/c/50a3933760b427759afdd23156a7280a19357a92 https://git.kernel.org/stable/c/93c5b8decc0ef39ba84f4211d2db6da0a4aefbeb https://git.kernel.org/stable/c/bf0b0c6d159767c0d1c21f793950d78486690ee0 https://git.kernel.org/stable/c/c24fa427fc0ae827b2a3a07f13738cbf82c3f851 https://git.kernel.org/stable/c/c9a75ec45f1111ef530ab186c2a7684d0a0c9245 https://git.kernel.org/stable/c/f04be6d68f715c1473a8422fc0460f57b5e99931

Other References

https://lists.debian.org/debian-lts-announce/2025/01/msg00001.html https://lists.debian.org/debian-lts-announce/2025/03/msg00002.html

Frequently Asked Questions

What is CVE-2024-50273? +

In the Linux kernel, the following vulnerability has been resolved: btrfs: reinitialize delayed ref list after deleting it from the list At insert_delayed_ref() if we need to update the action of an existing ref to BTRFS_DROP_DELAYED_REF, we delete the ref from its ref head's ref_add_list using list_del(), which leaves the ref's add_list member not reinitialized, as list_del() sets the next and prev members of the list to LIST_POISON1 and LIST_POISON2, respectively. If later we end up calling drop_delayed_ref() against the ref, which can happen during merging or when destroying delayed refs due to a transaction abort, we can trigger a crash since at drop_delayed_ref() we call list_empty() against the ref's add_list, which returns false since the list was not reinitialized after the list_del() and as a consequence we call list_del() again at drop_delayed_ref(). This results in an invalid list access since the next and prev members are set to poison pointers, resulting in a splat if CONFIG_LIST_HARDENED and CONFIG_DEBUG_LIST are set or invalid poison pointer dereferences otherwise. So fix this by deleting from the list with list_del_init() instead. It has a CVSS v3.1 base score of 5.5 (MEDIUM).

How severe is CVE-2024-50273? +

CVE-2024-50273 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-2024-50273? +

CVE-2024-50273 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-2024-50273? +

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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