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CVE-2024-50273

btrfs: reinitialize delayed ref list after deleting it from the list

Published: 11/19/2024 Last updated: 5/4/2025 Reserved: 10/21/2024

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.

CNA assigner: Linux (416baaa9-dc9f-4396-8d5f-8c081fb06d67) Requested by: n/a

Opam packages affected (27)

albatross cdrom conf-bpftool conf-libbpf conf-linux-libc-dev core core_unix hvsock mirage-block-unix mm ocaml-probes orun rawlink rawlink-eio rawlink-lwt shell solo5 solo5-bindings-hvt solo5-bindings-spt solo5-cross-aarch64 solo5-kernel-ukvm tracy-client tuntap uring vhd-format vhd-format-lwt xapi-stdext-unix

Products affected (2)

Product Vendor Version
Linux Linux < 6.2.7
Linux Linux n/a

References (8)