Re: [PATCH bpf] bpf: roll back stream capacity when allocation fails

[Pu Lehui]

On 2026/7/20 9:23, Jianlin Shi wrote:
> bpf_stream_push_str() accounts the string length before allocating a
> stream element. If the allocation fails, the length remains charged even
> though no element is queued and therefore cannot be released by a reader.
> Repeated failures can exhaust the stream capacity permanently until the
> BPF program is freed.
>
> Roll back the capacity charge when creating the stream element fails.
>
> Fixes: 5ab154f1463a ("bpf: Introduce BPF standard streams")
> Signed-off-by: Jianlin Shi <shijianlin11@xxxxxxxxxxx>
> ---
>   kernel/bpf/stream.c | 9 ++++++++-
>   1 file changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/bpf/stream.c b/kernel/bpf/stream.c
> index be9ce98e9..4b8a74b91 100644
> --- a/kernel/bpf/stream.c
> +++ b/kernel/bpf/stream.c
> @@ -79,7 +79,14 @@ static int bpf_stream_push_str(struct bpf_stream *stream, const char *str, int l
>   {
>   	int ret = bpf_stream_consume_capacity(stream, len);
>   
> -	return ret ?: __bpf_stream_push_str(&stream->log, str, len);
> +	if (ret)
> +		return ret;
> +
> +	ret = __bpf_stream_push_str(&stream->log, str, len);
> +	if (ret)
> +		atomic_sub(len, &stream->capacity);
> +
> +	return ret;
>   }
>   
>   static struct bpf_stream *bpf_stream_get(enum bpf_stream_id stream_id, struct bpf_prog_aux *aux)

looks good to me, but it might be better to target bpf-next, as this 
isn't a critical issue.