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Tue, 25 Aug 2026 04:39:55 -0700 (PDT) Received: from localhost.localdomain ([103.120.31.178]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-327f920e0desm6962043eec.24.2026.08.25.04.39.51 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Tue, 25 Aug 2026 04:39:55 -0700 (PDT) From: Khawar Ahemad To: bpf@vger.kernel.org Cc: linux-kernel@vger.kernel.org, ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, eddyz87@gmail.com, memxor@gmail.com, ahemadkhawar123@gmail.com Subject: [PATCH bpf-next] bpf: Fix stream capacity leak and spurious -ENOSPC in bpf_stream_stage_commit Date: Tue, 25 Aug 2026 17:09:48 +0530 Message-ID: <20260825113948.85020-1-ahemadkhawar123@gmail.com> X-Mailer: git-send-email 2.54.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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 --- 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 = bpf_stream_consume_capacity(stream, ss->len); if (ret) return ret; list = llist_del_all(&ss->log); - head = tail = list; - - if (!list) + if (!list) { + bpf_stream_release_capacity(stream, ss->len); return 0; + } + + head = list; + tail = list; while (llist_next(list)) { tail = llist_next(list); list = tail; -- 2.54.0 (Apple Git-157)