From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E57B27081E; Fri, 19 Jun 2026 00:27:17 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781828838; cv=none; b=Jp0fMUSHb4ugH5U2fFtcUyQGZSEXbspgi7wWJLvfdraTbOyDU3lTWTpPvD1r9it7Gqj73v+e3izAkyDpbOcGxxVICN34ayb2e3SBhpKbvyrD4MqwoIKpymQ2em+jgI/LqAsseNNamF6TjQZDt5xkmwV0G7srqyvi0IVMY6RFYq8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781828838; c=relaxed/simple; bh=vDiNoB63vp9CNN4dH7gwxlh25SsPTI+fA2yOTDC0cAE=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=qSPWq7gvfDi3+er5FIMz1L6Pquv6IwbwuXf/wvnJUyti7j81pyMUp2S7Sbweqyl1CPDtsXqL68xk9swcSlJDI5Y+912gg0hw6gXTt/9afoqBkpOrRE9rz4NlRrCyg5lYaMYL65jqnycvz0jXNU4kNg5h4xUHmi36L2kopU5mRu8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=jjUOGOcE; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="jjUOGOcE" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 907D61F000E9; Fri, 19 Jun 2026 00:27:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1781828837; bh=2tso89OAXLEG4abmFUORfnswxG8cXfUT2RyTgq1YXRE=; h=From:Date:Subject:References:In-Reply-To:To:Cc; b=jjUOGOcEqOqcejvrPh6f+kz5nWl5Tice/PTK+N6+oJaDOigYKQSD2jBJe6sGwcB74 Nc1ib5BtXKJLsq4kU5uL7osETYhfM/iCDsYt7X3L3hE5awuCmjLdceLbmzzHEd5K7x XhuxggqTxl4FDADfnZ2ubBc2DwAt0nVQHfXgUa7rM0aI/wBJdNw7Nyh8eMeyk3WuhN Zg+ZzO83/rpYXDIYPpg9RlSa0MBGKkrZfo922nX5qx5RyY+C5qhbwGfcc6HKBaabBj NCQiKleocR5/hUlWkjy4rfXxAOitQQAe8tq/HtiDyo3KQirFxn6krqeBztE18lDqyE HvW2ewd2+R1gA== From: Tamir Duberstein Date: Thu, 18 Jun 2026 20:26:42 -0400 Subject: [PATCH bpf v2 4/8] libbpf: ringbuf: Handle position counter wrap Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20260618-bpf-ringbuf-fixes-v2-4-33fde039ddf3@kernel.org> References: <20260618-bpf-ringbuf-fixes-v2-0-33fde039ddf3@kernel.org> In-Reply-To: <20260618-bpf-ringbuf-fixes-v2-0-33fde039ddf3@kernel.org> To: Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Martin KaFai Lau , Eduard Zingerman , Kumar Kartikeya Dwivedi , Song Liu , Yonghong Song , Jiri Olsa , Shuah Khan , Andrea Righi , Xu Kuohai , Andrea Righi , Bing-Jhong Billy Jheng , David Vernet Cc: bpf@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, Andrew Werner , Zvi Effron , Andrii Nakryiko , Emil Tsalapatis , Tamir Duberstein X-Mailer: b4 0.16-dev X-Developer-Signature: v=1; a=openpgp-sha256; l=1226; i=tamird@kernel.org; h=from:subject:message-id; bh=vDiNoB63vp9CNN4dH7gwxlh25SsPTI+fA2yOTDC0cAE=; b=owGbwMvMwCV2wYdPVfy60HTG02pJDFkmPdc2Ftg/39RZZHndX/dj58IylV5TtYMfLQ+4em7JO CeQ+aGhYyILgxgXg6WYIkui6KG96am398hmvjsOM4eVCWSItEgDAxCwMPDlJuaVGukY6ZlqG+oZ GukY6BgzcHEKwFT/u8jIcOn8FuapShOWd3K0cni0b50avUT06xHxaIOW+HS234818hn+yqpuCPa YLOtS07+tIaJ13ZKCwKinu/YIXBA+kRDpvOUxCwA= X-Developer-Key: i=tamird@kernel.org; a=openpgp; fpr=5A6714204D41EC844C50273C19D6FF6092365380 Ring buffer positions are unsigned long counters and can wrap on 32-bit systems. ringbuf_process_ring() stops consuming when producer_pos wraps below consumer_pos because it compares the counters by magnitude. Compare the positions for equality instead. The producer cannot move logically behind the consumer in a non-overwrite ring. Fixes: bf99c936f947 ("libbpf: Add BPF ring buffer support") Reported-by: Andrew Werner Assisted-by: Codex:gpt-5.5 Signed-off-by: Tamir Duberstein --- tools/lib/bpf/ringbuf.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/tools/lib/bpf/ringbuf.c b/tools/lib/bpf/ringbuf.c index 5737e02c1670..1c5bce2b5e12 100644 --- a/tools/lib/bpf/ringbuf.c +++ b/tools/lib/bpf/ringbuf.c @@ -274,7 +274,8 @@ static int64_t ringbuf_process_ring(struct ring *r, size_t n) do { got_new_data = false; prod_pos = smp_load_acquire(r->producer_pos); - while (cons_pos < prod_pos) { + /* Positions wrap; the consumer cannot logically pass the producer. */ + while (cons_pos != prod_pos) { len_ptr = r->data + (cons_pos & r->mask); len = smp_load_acquire(len_ptr); -- 2.55.0.rc0.159.gbe5d7338c2