CVE-2024-58088

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

bpf: Fix deadlock when freeing cgroup storage

The following commit bc235cdb423a ("bpf: Prevent deadlock from recursive bpftaskstorage[get|delete]") first introduced deadlock prevention for fentry/fexit programs attaching on bpftask_storage helpers. That commit also employed the logic in map free path in its v6 version.

Later bpfcgrpstorage was first introduced in c4bcfb38a95e ("bpf: Implement cgroup storage available to non-cgroup-attached bpf progs") which faces the same issue as bpftaskstorage, instead of its busy counter, NULL was passed to bpflocalstoragemapfree() which opened a window to cause deadlock:

<TASK>
    (acquiring local_storage->lock)
_raw_spin_lock_irqsave+0x3d/0x50
bpf_local_storage_update+0xd1/0x460
bpf_cgrp_storage_get+0x109/0x130
bpf_prog_a4d4a370ba857314_cgrp_ptr+0x139/0x170
? __bpf_prog_enter_recur+0x16/0x80
bpf_trampoline_6442485186+0x43/0xa4
cgroup_storage_ptr+0x9/0x20
    (holding local_storage->lock)
bpf_selem_unlink_storage_nolock.constprop.0+0x135/0x160
bpf_selem_unlink_storage+0x6f/0x110
bpf_local_storage_map_free+0xa2/0x110
bpf_map_free_deferred+0x5b/0x90
process_one_work+0x17c/0x390
worker_thread+0x251/0x360
kthread+0xd2/0x100
ret_from_fork+0x34/0x50
ret_from_fork_asm+0x1a/0x30
</TASK>

Progs: - A: SEC("fentry/cgroupstorageptr") - cgid (BPFMAPTYPEHASH) Record the id of the cgroup the current task belonging to in this hash map, using the address of the cgroup as the map key. - cgrpa (BPFMAPTYPECGRPSTORAGE) If current task is a kworker, lookup the above hash map using function parameter @owner as the key to get its corresponding cgroup id which is then used to get a trusted pointer to the cgroup through bpfcgroupfromid(). This trusted pointer can then be passed to bpfcgrpstorageget() to finally trigger the deadlock issue. - B: SEC("tpbtf/sysenter") - cgrpb (BPFMAPTYPECGRPSTORAGE) The only purpose of this prog is to fill Prog A's hash map by calling bpfcgrpstorageget() for as many userspace tasks as possible.

Steps to reproduce: - Run A; - while (true) { Run B; Destroy B; }

Fix this issue by passing its busy counter to the free procedure so it can be properly incremented before storage/smap locking.