CVE-2025-68742

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

bpf: Fix invalid prog->stats access when update_effective_progs fails

Syzkaller triggers an invalid memory access issue following fault

injection in update_effective_progs. The issue can be described as

follows:

__cgroup_bpf_detach

update_effective_progs

compute_effective_progs

bpf_prog_array_alloc <-- fault inject

purge_effective_progs

/* change to dummy_bpf_prog */

array->items[index] = &dummy_bpf_prog.prog

---softirq start---

__do_softirq

...

__cgroup_bpf_run_filter_skb

__bpf_prog_run_save_cb

bpf_prog_run

stats = this_cpu_ptr(prog->stats)

/* invalid memory access */

flags = u64_stats_update_begin_irqsave(&stats->syncp)

---softirq end---

static_branch_dec(&cgroup_bpf_enabled_key[atype])

The reason is that fault injection caused update_effective_progs to fail

and then changed the original prog into dummy_bpf_prog.prog in

purge_effective_progs. Then a softirq came, and accessing the members of

dummy_bpf_prog.prog in the softirq triggers invalid mem access.

To fix it, skip updating stats when stats is NULL.