In the Linux kernel, the following vulnerability has been resolved:
bpf: Skip unsettled links in link iterator
bpf_link_prime() inserts a link into link_idr before anon_inode_getfile()
succeeds and before bpf_link_settle() publishes the ID in link->id.
bpf_link_by_id() treats such an ID-zero link as unsettled, but the link
iterator takes a reference without this check.
If anon_inode_getfile() then fails, the creator removes the ID and frees
its still-private link directly. The iterator is left with a dangling
reference and its next bpf_link_put() accesses freed memory.
Treat ID-zero entries as transient in bpf_link_get_curr_or_next(), just as
bpf_link_by_id() does.
BUG: KASAN: slab-use-after-free in bpf_link_put
Write of size 8 by task exp/384
Call Trace:
bpf_link_put kernel/bpf/syscall.c:3372
bpf_link_seq_next kernel/bpf/link_iter.c:33
bpf_seq_read kernel/bpf/bpf_iter.c:158
vfs_read fs/read_write.c:572
ksys_read fs/read_write.c:716
do_syscall_64 arch/x86/entry/syscall_64.c:84
entry_SYSCALL_64_after_hwframe arch/x86/entry/entry_64.S:121
Kernel panic - not syncing: KASAN: panic_on_warn set ...