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 59E2D4CDDE1; Thu, 17 Sep 2026 15:46:43 +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=1789660008; cv=none; b=aFr2P3MHbLeLac/rVDg6DJRxrfIkRhR/p0YB3iMopjNCWsbJonoK28xbWls9nd05H2Ihs9GkQe5+MtujvoLZoy6rRGqNcghDKNjoyjkGAA71JYaeP/ajNUQmr6JRvyLS36glOilksgoTKKrP/+AibUMKKO8O2Q0sjokbQy8N3ac= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789660008; c=relaxed/simple; bh=7E59Jd4cjAzq0VmwBs9IwOu2Hp4Pq4SVq/bVjUIQcLc=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=GpFrZ/Yu2//BQwuE+3g1cytv3GW6PSyAmPSHGRpKiMTjNvUsrOdk5oNijK6POuFluXXtwA7bmTXl1nAlST1C33F/3J8IaHWMRrXmg56oJsDm/hO7uzC/zpF9R78cMeq2P6uuuyg+NDHxhLlKqrKf1yOGT94+pr3Jz7HuC9IkhnI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=f151Dgw4; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="f151Dgw4" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7C2111F000FF; Thu, 17 Sep 2026 15:46:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1789660003; bh=N7dzYvArPn+DYZ3Sq/Qf4+WsDJnGesFL6vYECMFVi+s=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=f151Dgw4+9eJSKwiFYYkCJfetUc16nU6Pbn9LZUJXFyK28Gn+6F8etsZ/O8lyKufb pcA+mQ8sDf0Z2lNUOKTjCRuJmp6lyZO2zlNRqvXYxBua/+eWpljGlnhPJ9ae84fKt9 pDJwDj4BrF+cjqU1BsdWCqYgts1vUIl2oNnp1Ew4= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Vincent Donnefort , Steven Rostedt , Sasha Levin Subject: [PATCH 7.2 445/733] tracing/remotes: Account for ring buffer page header in size calculation Date: Thu, 17 Sep 2026 16:12:33 +0100 Message-ID: <20260917151402.976096927@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260917151350.597953846@linuxfoundation.org> References: <20260917151350.597953846@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 7.2-stable review patch. If anyone has any objections, please let me know. ------------------ From: Vincent Donnefort [ Upstream commit 442ffa742daa65a0e8fe003abe9fbe472366e4de ] 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). Link: https://patch.msgid.link/20260911193937.602202-2-vdonnefort@google.com Fixes: 2e67fabd8b77 ("ring-buffer: Introduce ring-buffer remotes") Signed-off-by: Vincent Donnefort Signed-off-by: Steven Rostedt Signed-off-by: Sasha Levin --- 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 afc7daa6ee7dc..11bffb6a142d1 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 e6724f947170d..0e8ca62301040 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; -- 2.53.0