🛡️ AZL-53775 — kernel

CVE-2024-50273 affecting package kernel for versions less than 5.15.173.1-1

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.