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 87EE426E6F3; Sun, 14 Jun 2026 01:49:03 +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=1781401744; cv=none; b=FZQozTd1GNsklbk187t2UIpmU2PPwDlL/eGKqx8ca5XKH8vJtEg0B34ykkSN+RIFd4apt/jb74pNL35lOpP/9nX+yTsXLsb1aSUjLkDpW+souZbroFsaywisViGVhrHVlfBg5g/T+d2JN5uq1HWr5b/OMSLvvIvv1ZhLbsOTrEU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781401744; c=relaxed/simple; bh=ild0iTxSm4VS5EwjCoCAWpgySpEcrcLmiLWVzBUlz6o=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=MVeJd3ugV77kVjhH58uIAlZGp48c0YOSg9n9DNu+Tup9yLJGO/lscjlVjhU9jDdcAiVu14NDrR1rGU3xhwSGQ0EtYq/nCQa3Xthj4WQi2pUyO3MIsqTRqQS0jqXfpNfxrEBF7dGhQKT1OH/aju8a5psixNiNioazTgUp4CwQ6U8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=DA6zF6Pp; 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="DA6zF6Pp" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6DBAC1F000E9; Sun, 14 Jun 2026 01:49:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1781401743; bh=BC7V621uLpV43rs4Jsxzy0oM9i8RWW4+PZ721ooD5GE=; h=From:Date:Subject:References:In-Reply-To:To:Cc; b=DA6zF6Pp/QuECrKO2R8MAGbIkZeBn4rk9vYEz6e/h6sNut7YyoQvDZHKarVS3K6zj Z2KdYeHFasQvGaBCVppknr9qtoMxviHsNqBo0RnvUYdbUXlRIj6oHRUCw5AGqSj6Ea 5WeKkFbw9wErd2P9mTMAbStfgsadTVeKib6oeMzTfFY6Pl14aH4cDKgIuVMYFAyA07 G7dTcoL6TAAa7GBWRJXffgoss4i5YgsyApFRkn8JmaFp8kQyNv4cnpoVtXhs11Fphs ssFkWRDJQURQdLXFZcHe2D1TLBMVAbwETIz5ydd6gM1pDQBrZMOQeR41r2mSzrMceE /JWUkB8OAEwXg== From: Tamir Duberstein Date: Sat, 13 Jun 2026 21:48:46 -0400 Subject: [PATCH bpf 3/6] libbpf: ringbuf: Handle position counter wrap Precedence: bulk X-Mailing-List: bpf@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: <20260613-bpf-ringbuf-fixes-v1-3-e623481cb724@kernel.org> References: <20260613-bpf-ringbuf-fixes-v1-0-e623481cb724@kernel.org> In-Reply-To: <20260613-bpf-ringbuf-fixes-v1-0-e623481cb724@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 Cc: bpf@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, Andrew Werner , Zvi Effron , Andrii Nakryiko , Tamir Duberstein X-Mailer: b4 0.16-dev X-Developer-Signature: v=1; a=openpgp-sha256; l=1148; i=tamird@kernel.org; h=from:subject:message-id; bh=ild0iTxSm4VS5EwjCoCAWpgySpEcrcLmiLWVzBUlz6o=; b=owGbwMvMwCV2wYdPVfy60HTG02pJDFl6HG3GxqJxG/4d/bn1aO3cKTzls2bKG9/9Pyco4hbX7 NLXCfI7OiayMIhxMViKKbIkih7am556e49s5rvjMHNYmUCGSIs0MAABCwNfbmJeqZGOkZ6ptqGe oZGOgY4xAxenAEz1kkuMDH9d5B4/eSqlrrd6lWhiwwyxz19eGnyeXyH09+mhlSUsM78wMixoObd Ye2bC9XO9sjlBm860nPB58dmrivmazidWjcSdfSwA 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 | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/tools/lib/bpf/ringbuf.c b/tools/lib/bpf/ringbuf.c index ae7fa79b6217..b7adce37b519 100644 --- a/tools/lib/bpf/ringbuf.c +++ b/tools/lib/bpf/ringbuf.c @@ -268,7 +268,7 @@ 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) { + while (cons_pos != prod_pos) { len_ptr = r->data + (cons_pos & r->mask); len = smp_load_acquire(len_ptr); -- 2.55.0.rc0.96.gc050c23164