CVE-2024-50273 Information

Nov 20, 2024 cve

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.

Reference

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