From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-ej1-f72.google.com (mail-ej1-f72.google.com [209.85.218.72]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 07A695616DE for ; Fri, 11 Sep 2026 19:39:56 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.218.72 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789155604; cv=none; b=oXI5adlO1fRoHotUGV6kVqX/vUNAue6BqcL9jb0znIdd4T6W9YqgeCBd6T4HDFThzVL7eUXV3SblhbrilaRYf6nVoqpcmH5noRGGqaJc09aaujko3/4zltQMjakqJqC0MOALXvRAWzM5iZ9SFr4laSnx8sbRU/ba8uQlp9V/4hI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789155604; c=relaxed/simple; bh=p/PNA9lb1ujgnjktgM201CRXtbHR6ZSSOZ1hHyPZfg4=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=Ru0iKNuZmC6x9EoqM1tlEL/Ssq3UAn3UGh75Io3gnOtSR8ug/BR2znBbYflQSTyXUr4LH1QMOzn4h/Wg1yLaGeTthRqvBta+9lhkP/suI61OENO81gH1JfYhlIA5EuUNzk3ZxlTxCX+XMCUlpOnTuxNq7pg4QkO02/PVYiBqDmw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--vdonnefort.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=UoDyFOQj; arc=none smtp.client-ip=209.85.218.72 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--vdonnefort.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="UoDyFOQj" Received: by mail-ej1-f72.google.com with SMTP id a640c23a62f3a-c2939e341f7so156193766b.2 for ; Fri, 11 Sep 2026 12:39:55 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1789155593; x=1789760393; darn=vger.kernel.org; h=content-type:cc:to:from:subject:message-id:references:mime-version :in-reply-to:date:from:to:cc:subject:date:message-id:reply-to :content-type; bh=WeMy/DaNVJkSXZ0N2fL3KCM+KXX4amcR67/b0vTZpco=; b=UoDyFOQjNmHA1HUmVNlBfCpdLI4VuGA2MJEe62TAs68xZyToe4JdePa2HKFpXbwH54 eu502RxzOqqpJTzbHHlNr4jdXh0wZfHTgdQRxSRSLv0YHsa4JEl4pfYAYALAWHJ/cVN2 xOy97sOmVOe1oqT32+SItDHs/OMcSWHIV2HOiHPzE+tqleRwABNU45tySQo73yGmb/qi uKyd0oWswPRD+Bbi1qgdV5lE443FrEr+uKqAzT8JW4YTPnNobrvdql5DwcTZOdQxosPb ccxkZcU1hKWYYEjyHwSaR5C/wZbLiraaBGmpao6zPR+PSk46iK7v2Vr/C/WPUu6ps7cn MaAg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1789155593; x=1789760393; h=content-type:cc:to:from:subject:message-id:references:mime-version :in-reply-to:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to:content-type; bh=WeMy/DaNVJkSXZ0N2fL3KCM+KXX4amcR67/b0vTZpco=; b=QTBtMcoMzJ29akZW79wSrvQAgKq9l4tQdyUyBAP/4YzgilHkSzr2JkSQupXAUxOj3X +dMkpITtInPgRHB8Ufu4pFPdRie/IaXsydpI+ImoNOk9YBvXT1A1QwiDADG0TCqM5fo9 OrrN11KRQ4tGiz/Zw8NqocM0n913/S35tvvEJlaortRzq9b0Pc6rsjbJyYSvOGwYLdEz QaF+wLsYIiAIOFQp/7HzfTjJRk9ZPaWLJL3Mw40oqM0c+ayH2TsdM+lro5ZCgljgmnMW Zex3dOOww9IEO6JXh4ZTRW2Bf/muq0lHOMwUtlngdCGY5X7hRAq1XAko4ScIdD7l/QFF T4Hg== X-Forwarded-Encrypted: i=1; AKwUvBzKrf7aQOfii1B/nNVWyXlBDg+IGl5PXX1ok6UUKWoqV2y60gNbhb3HF9A+LahoIEWxq6U/ICqNzYmMsdc=@vger.kernel.org X-Gm-Message-State: AFuF++nlh43nfaWiNVOfjTyJiquGrxp7e7eZJs78G0BX1cT/e5FLegoy vY91SqvTIEM0+DyBlf0a6C7yRwmGGopnZZNh5p2zGRe+sB7YzNgQJyCWcW051KNQZsbwvRqf7uG voBznpFkzaoEdCovzqxLe7A== X-Received: from ejbox4.prod.google.com ([2002:a17:907:1004:b0:c29:6e48:1427]) (user=vdonnefort job=prod-delivery.src-stubby-dispatcher) by 2002:a17:906:c14f:b0:c29:4d53:787f with SMTP id a640c23a62f3a-c2966737ef4mr240602566b.41.1789155592434; Fri, 11 Sep 2026 12:39:52 -0700 (PDT) Date: Fri, 11 Sep 2026 20:39:35 +0100 In-Reply-To: <20260911193937.602202-1-vdonnefort@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20260911193937.602202-1-vdonnefort@google.com> X-Mailer: git-send-email 2.55.0.1007.g17ff1f9808-goog Message-ID: <20260911193937.602202-2-vdonnefort@google.com> Subject: [PATCH v2 1/3] tracing/remotes: Account for ring buffer page header in size calculation From: Vincent Donnefort To: rostedt@goodmis.org, mhiramat@kernel.org, linux-trace-kernel@vger.kernel.org Cc: mathieu.desnoyers@efficios.com, kernel-team@android.com, linux-kernel@vger.kernel.org, Vincent Donnefort Content-Type: text/plain; charset="UTF-8" trace_buffer_desc_size() and trace_remote_alloc_buffer undercount the required pages because every ring buffer page contains a header (BUF_PAGE_HDR_SIZE). Account for that header to ensure allocated remote ring buffers aren't smaller than requested by the user. The newly introduced helper __calc_nr_pages_ring_buffer_desc() can return a value that overflows the descriptor nr_pages field (32 bits). Fixes: 2e67fabd8b77 ("ring-buffer: Introduce ring-buffer remotes") Signed-off-by: Vincent Donnefort --- include/linux/ring_buffer.h | 15 +++++++++++++-- kernel/trace/trace_remote.c | 2 +- 2 files changed, 14 insertions(+), 3 deletions(-) diff --git a/include/linux/ring_buffer.h b/include/linux/ring_buffer.h index afc7daa6ee7d..11bffb6a142d 100644 --- a/include/linux/ring_buffer.h +++ b/include/linux/ring_buffer.h @@ -3,8 +3,9 @@ #define _LINUX_RING_BUFFER_H #include -#include #include +#include +#include #include @@ -279,9 +280,19 @@ static inline struct ring_buffer_desc *__first_ring_buffer_desc(struct trace_buf return (struct ring_buffer_desc *)(&desc->__data[0]); } +/* + * Returns the number of pages for a ring_buffer_desc. The caller must ensure it + * does not overflow ring_buffer_desc::nr_page_va. + */ +static inline unsigned long __calc_nr_pages_ring_buffer_desc(size_t size) +{ + /* Takes into account the reader page */ + return max(DIV_ROUND_UP(size, PAGE_SIZE - BUF_PAGE_HDR_SIZE), 2UL) + 1; +} + static inline size_t trace_buffer_desc_size(size_t buffer_size, unsigned int nr_cpus) { - unsigned int nr_pages = max(DIV_ROUND_UP(buffer_size, PAGE_SIZE), 2UL) + 1; + unsigned long nr_pages = __calc_nr_pages_ring_buffer_desc(buffer_size); struct ring_buffer_desc *rbdesc; return size_add(offsetof(struct trace_buffer_desc, __data), diff --git a/kernel/trace/trace_remote.c b/kernel/trace/trace_remote.c index 75fa1ffc4c96..c17902e42ef1 100644 --- a/kernel/trace/trace_remote.c +++ b/kernel/trace/trace_remote.c @@ -980,7 +980,7 @@ int trace_remote_alloc_buffer(struct trace_buffer_desc *desc, size_t desc_size, const struct cpumask *cpumask) { size_t min_desc_size = trace_buffer_desc_size(buffer_size, cpumask_weight(cpumask)); - unsigned int nr_pages = max(DIV_ROUND_UP(buffer_size, PAGE_SIZE), 2UL) + 1; + unsigned int nr_pages = __calc_nr_pages_ring_buffer_desc(buffer_size); struct ring_buffer_desc *rb_desc; int cpu, ret = -ENOMEM; -- 2.55.0.1007.g17ff1f9808-goog