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[192.26.29.3]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-c24962a3c13sm1833208266b.26.2026.08.25.05.18.56 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 25 Aug 2026 05:18:57 -0700 (PDT) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=UTF-8 Date: Tue, 25 Aug 2026 14:18:56 +0200 Message-Id: To: "Khawar Ahemad" , Cc: , , , , Subject: Re: [PATCH bpf-next] bpf: Fix stream capacity leak and spurious -ENOSPC in bpf_stream_stage_commit From: "Kumar Kartikeya Dwivedi" X-Mailer: aerc 0.21.0 References: <20260825113948.85020-1-ahemadkhawar123@gmail.com> In-Reply-To: <20260825113948.85020-1-ahemadkhawar123@gmail.com> On Tue Aug 25, 2026 at 1:39 PM CEST, Khawar Ahemad wrote: > bpf_stream_stage_commit() accounts the staged string length against > the stream capacity via bpf_stream_consume_capacity() before > detaching the queued elements with llist_del_all(). > > If no elements are returned by llist_del_all() (for instance, when > the staging list was empty or failed to allocate elements), the > function returns early without releasing the consumed capacity. > Because no elements are queued into stream->log, no reader will ever > pop or release this capacity, leading to a permanent capacity leak. > > Furthermore, if ss->len is 0, bpf_stream_consume_capacity() is invoked > needlessly and fails with -ENOSPC if the stream is currently at > capacity, spuriously rejecting a zero-byte commit. > > Fix both issues by: > 1. Returning early if ss->len is 0. > 2. Rolling back the consumed capacity with bpf_stream_release_capacity() > if llist_del_all() returns NULL. > > Fixes: 5ab154f1463a ("bpf: Introduce BPF standard streams") > Signed-off-by: Khawar Ahemad > --- Completely unnecessary. pw-bot: cr > kernel/bpf/stream.c | 12 +++++++++--- > 1 file changed, 9 insertions(+), 3 deletions(-) > > diff --git a/kernel/bpf/stream.c b/kernel/bpf/stream.c > index 7a5c3ac867..3ad58c8284 100644 > --- a/kernel/bpf/stream.c > +++ b/kernel/bpf/stream.c > @@ -350,15 +350,21 @@ int bpf_stream_stage_commit(struct bpf_stream_stage= *ss, struct bpf_prog *prog, > if (!stream) > return -EINVAL; > > + if (!ss->len) > + return 0; > + > ret =3D bpf_stream_consume_capacity(stream, ss->len); > if (ret) > return ret; > > list =3D llist_del_all(&ss->log); > - head =3D tail =3D list; > - > - if (!list) > + if (!list) { > + bpf_stream_release_capacity(stream, ss->len); > return 0; > + } > + > + head =3D list; > + tail =3D list; > while (llist_next(list)) { > tail =3D llist_next(list); > list =3D tail;