Affected: Linux

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

bpf: Add bpf_prog_run_data_pointers()

syzbot found that cls_bpf_classify() is able to change tc_skb_cb(skb)->drop_reason triggering a warning in sk_skb_reason_drop().

WARNING: CPU: 0 PID: 5965 at net/core/skbuff.c:1192 __sk_skb_reason_drop net/core/skbuff.c:1189 [inline] WARNING: CPU: 0 PID: 5965 at net/core/skbuff.c:1192 sk_skb_reason_drop+0x76/0x170 net/core/skbuff.c:1214

struct tc_skb_cb has been added in commit ec624fe740b4 ("net/sched: Extend qdisc control block with tc control block"), which added a wrong interaction with db58ba459202 ("bpf: wire in data and data_end for cls_act_bpf").

drop_reason was added later.

Add bpf_prog_run_data_pointers() helper to save/restore the net_sched storage colliding with BPF data_meta/data_end.