Commit 3f23ee55 authored by Eduard Zingerman's avatar Eduard Zingerman Committed by Alexei Starovoitov
Browse files

selftests/bpf: test for changing packet data from global functions 

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: default avatarNick Zavaritsky <mejedi@gmail.com>
Signed-off-by: default avatarEduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20241210041100.1898468-5-eddyz87@gmail.com


Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent 51081a3f

tools/testing/selftests/bpf/progs/verifier_sock.c

+28 −0
Original line number Diff line number Diff line
@@ -1037,4 +1037,32 @@ __naked void sock_create_read_src_port(void) 
	: __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";