Kumar reported a KASAN splat in tcp_v6_rcv:
bash-5.2# ./test_progs -t btf_skc_cls_ingress
...
[ 51.810085] BUG: KASAN: slab-out-of-bounds in tcp_v6_rcv+0x2d7d/0x3440
[ 51.810458] Read of size 2 at addr ffff8881053f038c by task test_progs/226
The problem is that inet[6]_steal_sock accesses sk->sk_protocol without
accounting for request or timewait sockets. To fix this we can't just
check sock_common->skc_reuseport since that flag is present on timewait
sockets.
Instead, add a fullsock check to avoid the out of bands access of sk_protocol.
Fixes: 9c02bec959 ("bpf, net: Support SO_REUSEPORT sockets with bpf_sk_assign")
Reported-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Signed-off-by: Lorenz Bauer <lmb@isovalent.com>
Link: https://lore.kernel.org/r/20230815-bpf-next-v2-1-95126eaa4c1b@isovalent.com
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
8897562f67