From: Eduard Zingerman eddyz87@gmail.com
commit 3f23ee5590d9605dbde9a5e1d4b97637a4803329 upstream.
Check if verifier is aware of packet pointers invalidation done in global functions. Based on a test shared by Nick Zavaritsky in [0].
[0] https://lore.kernel.org/bpf/0498CA22-5779-4767-9C0C-A9515CEA711F@gmail.com/
Suggested-by: Nick Zavaritsky mejedi@gmail.com Signed-off-by: Eduard Zingerman eddyz87@gmail.com Link: https://lore.kernel.org/r/20241210041100.1898468-5-eddyz87@gmail.com Signed-off-by: Alexei Starovoitov ast@kernel.org Signed-off-by: Shung-Hsi Yu shung-hsi.yu@suse.com --- .../selftests/bpf/progs/verifier_sock.c | 28 +++++++++++++++++++ 1 file changed, 28 insertions(+)
diff --git a/tools/testing/selftests/bpf/progs/verifier_sock.c b/tools/testing/selftests/bpf/progs/verifier_sock.c index ee76b51005ab..e85f0f1deac7 100644 --- a/tools/testing/selftests/bpf/progs/verifier_sock.c +++ b/tools/testing/selftests/bpf/progs/verifier_sock.c @@ -977,4 +977,32 @@ l1_%=: r0 = *(u8*)(r7 + 0); \ : __clobber_all); }
+__noinline +long skb_pull_data2(struct __sk_buff *sk, __u32 len) +{ + return bpf_skb_pull_data(sk, len); +} + +__noinline +long skb_pull_data1(struct __sk_buff *sk, __u32 len) +{ + return skb_pull_data2(sk, len); +} + +/* global function calls bpf_skb_pull_data(), which invalidates packet + * pointers established before global function call. + */ +SEC("tc") +__failure __msg("invalid mem access") +int invalidate_pkt_pointers_from_global_func(struct __sk_buff *sk) +{ + int *p = (void *)(long)sk->data; + + if ((void *)(p + 1) > (void *)(long)sk->data_end) + return TCX_DROP; + skb_pull_data1(sk, 0); + *p = 42; /* this is unsafe */ + return TCX_PASS; +} + char _license[] SEC("license") = "GPL";