CVE-2024-50273btrfs: reinitialize delayed ref list after deleting it from the list

Official 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.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/2fd0948a483e9cb2d669c7199bc620a21c97673d
• 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/2cb1a73d1d44a1c11b0ee5eeced765dd80ec48e6
• https://git.kernel.org/stable/c/f04be6d68f715c1473a8422fc0460f57b5e99931
• https://git.kernel.org/stable/c/50a3933760b427759afdd23156a7280a19357a92
• https://git.kernel.org/stable/c/c9a75ec45f1111ef530ab186c2a7684d0a0c9245
• https://lists.debian.org/debian-lts-announce/2025/03/msg00002.html
• https://lists.debian.org/debian-lts-announce/2025/01/msg00001.html