CVE-2024-56664 — bpf, sockmap: Fix race between element replace and close()

Affected: Linux

In the Linux kernel, the following vulnerability has been resolved:

bpf, sockmap: Fix race between element replace and close()

Element replace (with a socket different from the one stored) may race with socket's close() link popping & unlinking. __sock_map_delete() unconditionally unrefs the (wrong) element:

// set map[0] = s0 map_update_elem(map, 0, s0)

// drop fd of s0 close(s0) sock_map_close() lock_sock(sk) (s0!) sock_map_remove_links(sk) link = sk_psock_link_pop() sock_map_unlink(sk, link) sock_map_delete_from_link // replace map[0] with s1 map_update_elem(map, 0, s1) sock_map_update_elem (s1!) lock_sock(sk) sock_map_update_common psock = sk_psock(sk) spin_lock(&stab->lock) osk = stab->sks[idx] sock_map_add_link(..., &stab->sks[idx]) sock_map_unref(osk, &stab->sks[idx]) psock = sk_psock(osk) sk_psock_put(sk, psock) if (refcount_dec_and_test(&psock))…

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CVE-2024-56664 — bpf, sockmap: Fix race between element replace and close()