On Tue, 2026-04-14 at 19:23 +0800, KaFai Wan wrote: AI is right and I'm late for the issue. Please ignore this. Sorry for the noise.
> A BPF_SOCK_OPS program can enable > BPF_SOCK_OPS_WRITE_HDR_OPT_CB_FLAG and then call > bpf_setsockopt(TCP_NODELAY) from BPF_SOCK_OPS_HDR_OPT_LEN_CB. > > That reaches __tcp_sock_set_nodelay(), which may call > tcp_push_pending_frames(). The transmit path then computes TCP > options again, re-enters bpf_skops_hdr_opt_len(), and invokes the > same BPF callback recursively. This can loop until the kernel > stack overflows. > > TCP_NODELAY is not safe from the header option callback context. > Reject it with -EOPNOTSUPP when TCP header option callbacks are > enabled on the socket, so the callback cannot recurse back into > tcp_push_pending_frames() through do_tcp_setsockopt(). > > Reported-by: Quan Sun <[email protected]> > Reported-by: Yinhao Hu <[email protected]> > Reported-by: Kaiyan Mei <[email protected]> > Closes: > https://lore.kernel.org/bpf/[email protected]/ > Fixes: 7e41df5dbba2 ("bpf: Add a few optnames to bpf_setsockopt") > Signed-off-by: KaFai Wan <[email protected]> > --- > net/ipv4/tcp.c | 5 ++++- > 1 file changed, 4 insertions(+), 1 deletion(-) > > diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c > index 202a4e57a218..7ac4c98be19d 100644 > --- a/net/ipv4/tcp.c > +++ b/net/ipv4/tcp.c > @@ -4004,7 +4004,10 @@ int do_tcp_setsockopt(struct sock *sk, int level, int > optname, > > switch (optname) { > case TCP_NODELAY: > - __tcp_sock_set_nodelay(sk, val); > + if (val && BPF_SOCK_OPS_TEST_FLAG(tp, > BPF_SOCK_OPS_WRITE_HDR_OPT_CB_FLAG)) > + err = -EOPNOTSUPP; > + else > + __tcp_sock_set_nodelay(sk, val); > break; > > case TCP_THIN_LINEAR_TIMEOUTS: -- Thanks, KaFai
