Re: [PATCH v4 bpf-next 10/10] selftest: bpf: Add test for bpf_tcp_ops.{enqueue,dequeue}_rcvq().

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] selftest: bpf: tcp_autolowat missing rpc_desc_buff_len reset
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commit 379ea90d2efb24d101b9be64b55e86c49d5beee6
Author: Kuniyuki Iwashima <kuniyu@google.com>

selftest: bpf: Add test for bpf_tcp_ops.{enqueue,dequeue}_rcvq().

This commit introduces a BPF selftest to verify the behavior of the
bpf_tcp_ops enqueue and dequeue callbacks dynamically adjusting sk_rcvlowat
for RPC frames. It sets up a client-server connection within a cgroup and
uses setsockopt with a custom BPF option to enable TCP AutoLOWAT.

> diff --git a/tools/testing/selftests/bpf/progs/tcp_autolowat.c b/tools/testing/selftests/bpf/progs/tcp_autolowat.c
> new file mode 100644
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/progs/tcp_autolowat.c

[ ... ]

> +static int tcp_init_autolowat_cb(struct bpf_tcp_sock *btp)
> +{
> +	struct tcp_autolowat_cb *cb;
> +	struct tcp_sock *tp;
> +
> +	cb = bpf_sk_storage_get(&tcp_autolowat_map, btp, 0,
> +				BPF_SK_STORAGE_GET_F_CREATE);
> +	if (!cb)
> +		return -1;
> +
> +	tp = bpf_core_cast(btp, struct tcp_sock);
> +
> +	cb->rpc_desc_seq = tp->copied_seq;
> +	cb->rpc_end_seq = tp->copied_seq;
> +#ifdef DEBUG
> +	cb->isn = tp->copied_seq;
> +#endif
> +

[Severity: Medium]
Should cb->rpc_desc_buff_len be reset to 0 here as well?

If an application re-initializes parsing by calling setsockopt again on
the same socket, tcp_init_autolowat_cb() resets the sequence numbers but 
leaves the buffer length intact. If the storage entry already existed 
from a previous operation that had read a partial RPC descriptor, the stale 
parser state will persist and could corrupt the next parse operation.

> +	return bpf_tcp_ops_set_flags((struct tcp_sock *)btp,
> +				     BPF_TCP_OPS_FLAG_RCVQ, 0);
> +}

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Sashiko AI review · https://sashiko.dev/#/patchset/20261006192601.1875100-1-kuniyu@google.com?part=10