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

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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>
This commit is contained in:
Eduard Zingerman 2024-12-09 20:10:56 -08:00 committed by Alexei Starovoitov
parent 51081a3f25
commit 3f23ee5590
1 changed files with 28 additions and 0 deletions
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28
tools/testing/selftests/bpf/progs/verifier_sock.c
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@ -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";