From 1ed69a54d31848618131aaf3311a78adbe78ced0 Mon Sep 17 00:00:00 2001 From: Emil Tsalapatis Date: Tue, 22 Sep 2026 17:20:23 +0000 Subject: [PATCH] selftests/bpf: Test rejection of pkt args to mutating subprogs Add a selftests that ensures that PTR_TO_PACKET arguments can only be passed to subprogs that will never adjust the underlying packet memory, and are rejected otherwise. Signed-off-by: Emil Tsalapatis Signed-off-by: Alexei Starovoitov Link: https://patch.msgid.link/20260922172028.6269-7-emil@etsalapatis.com --- .../bpf/progs/verifier_global_ptr_args.c | 53 +++++++++++++++++++ 1 file changed, 53 insertions(+) diff --git a/tools/testing/selftests/bpf/progs/verifier_global_ptr_args.c b/tools/testing/selftests/bpf/progs/verifier_global_ptr_args.c index a3d2af8dc839..dcc2dd46751a 100644 --- a/tools/testing/selftests/bpf/progs/verifier_global_ptr_args.c +++ b/tools/testing/selftests/bpf/progs/verifier_global_ptr_args.c @@ -350,4 +350,57 @@ int anything_to_untrusted_mem(void *ctx) return 0; } +struct pkt_arg { + __u64 x; + __u8 pad[56]; +}; + +__weak int subprog_pkt_ptr_no_change(struct pkt_arg *p) +{ + if (!p) + return 0; + + return p->x; +} + +SEC("?tc") +__success +int pkt_ptr_to_global_mem_arg_no_change(struct __sk_buff *skb) +{ + void *data = (void *)(long)skb->data; + void *data_end = (void *)(long)skb->data_end; + struct pkt_arg *p = data; + + if ((void *)(p + 1) > data_end) + return 0; + + return subprog_pkt_ptr_no_change(p); +} + +__weak int subprog_pkt_ptr_changes_data(struct __sk_buff *skb __arg_ctx, + struct pkt_arg *p) +{ + if (!p) + return 0; + + bpf_skb_pull_data(skb, 0); + return p->x; +} + +SEC("?tc") +__failure __log_level(2) +__msg("R2 is a packet pointer, but func#{{[0-9]+}} may change packet data") +__msg("Caller passes invalid args into func#{{[0-9]+}} ('subprog_pkt_ptr_changes_data')") +int pkt_ptr_to_global_mem_arg_changes_data(struct __sk_buff *skb) +{ + void *data = (void *)(long)skb->data; + void *data_end = (void *)(long)skb->data_end; + struct pkt_arg *p = data; + + if ((void *)(p + 1) > data_end) + return 0; + + return subprog_pkt_ptr_changes_data(skb, p); +} + char _license[] SEC("license") = "GPL";