From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=209.85.128.50 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794663297; b=RLvnosyrFyv0QTOH/5hqp9RhWypmZwiZjqq9yrSdfjifLArVz++KN9+oGstNgFGNaBZJ e1eNBAc0BrGwMCnQa1kF9fciyQCB0m0ukiIWnGr/+fx8ABMsVI83ZfJnreSw0FgZAufmK PTFZBOPmPOpwWIiQdIGqJpYy5BufMrxBzeXdVX8pJZAUbMv3EhayocbwC0tTZLGcw32FK Q/uJOwroHrI6WaMcLv2hgG36DmTEJvrWNtvOMdCjXsqxxOcxko7DPjr0U/9pP9V/eyUwT BFLYGfimlWVgyJDJFIHR2sl2lQKjcvI8Dk02kl2urXu+3HcJk96+NJAx83uyomks9hw== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794663297; h=DMARC-Filter:Received:DKIM-Signature:X-Google-DKIM-Signature: X-Gm-Message-State:X-Gm-Gg:X-Received:Received:Date:From:To:Cc: Subject:Message-ID:References:MIME-Version:Content-Type: Content-Disposition:Content-Transfer-Encoding:In-Reply-To; bh=iITVNj1hA8VysTM3SegZsQpdbGDdaeAWi8dvud7vL4Q=; b=0O2hDrJlshFMTGCd0iRNMgx7PfhyBzemQl1mbvEgC37zI6rpu+doYQ7Dcoxsua9Sbgbf wAuY0Yn9J2pam+d0qx2lonzCyqBOUhOpmnn55ue7QPZLvckGhJRDAb5ZpyO3CKT0AdDik WOSi4psBrO626afWExjh2oBhEdF/ysJ9vyrLw7/5IHDvNpWDxZCKrMW/zq1RmnG7pwWf0 c5iX5AsVMHbBRphqmlVvIZBsJn6zqFH/14HIh4DDo0qnNyI3cRhHuS/OQCtsTx4QyYhPi kg1g991TxqdCIYIWnkI674I2OLZ/jrkuIt8RVo3sApyma3AP8sx/KrJVZKDduQHZCfg== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass header.from=google.com; spf=pass smtp.mailfrom=google.com; dkim=pass header.d=google.com header.i=@google.com header.a=rsa-sha256 header.s=20260707 header.b=hugtNYNL; arc=none smtp.remote-ip=209.85.128.50 Received: from mail-wm1-f50.google.com (mail-wm1-f50.google.com [209.85.128.50]) (using TLSv1.3 with cipher TLS_AES_128_GCM_SHA256 (128/128 bits) key-exchange X25519 server-signature ECDSA (prime256v1) server-digest SHA256) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 1F804606A327 for ; Sat, 14 Nov 2026 13:34:56 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.2 smtp.subspace.kernel.org 1F804606A327 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=google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.a=rsa-sha256 header.s=20260707 header.b=hugtNYNL Received: by mail-wm1-f50.google.com with SMTP id 5b1f17b1804b1-4bb64c99d2fso4738715e9.3 for ; Sat, 14 Nov 2026 05:34:56 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20260707; t=1794663295; x=1795268095; darn=vger.kernel.org; h=in-reply-to:content-transfer-encoding:content-disposition :content-type:mime-version:references:message-id:subject:cc:to:from :date:from:to:cc:subject:date:message-id:reply-to:content-type; bh=iITVNj1hA8VysTM3SegZsQpdbGDdaeAWi8dvud7vL4Q=; b=hugtNYNLAMlBFGDbNiKjsl6/gjLlQ9FOn/PXyiCRua3kHES8n4nKD7kGcra2ssguCT 9pP4XOK1XQC1+H7kRly3Gjr5xGHoCE6S7vWkntXq5GNgq306NfW+exOUbmTnC/fw4mzr 3uVw6A+OWvgaqjrjX72Ycgigpmz+oTIpVA3pS/SuXAViIlD/PNoai8X4vHEJlCghZlPv 7ba7uA3a/FTMlHa5ziX093EAnMLLt4BrHoboZT6uSeOdz1vwZzfL3eRQgbGXkWUGgF8E TymS74/xaqb+3C1WHxVWc8T1m/lCGAPVTguLpIaVAm5ER6i/vEut/fjXeKEnV7qpcms2 vntg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20260707; t=1794663295; x=1795268095; h=in-reply-to:content-transfer-encoding:content-disposition :content-type:mime-version:references:message-id:subject:cc:to:from :date:x-gm-gg:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to:content-type; bh=iITVNj1hA8VysTM3SegZsQpdbGDdaeAWi8dvud7vL4Q=; b=VT1C3hY7ysB8VwRFYkh4TId4G+PAvzRLiFfHG7y/sklxoBypVAIxDbgKFwKtuVxGPJ 4UshfZ3Y6UjpkDpaX0YhkpBXRXGHFULWlbocSgQ859A1k/UP6BGIXV/e/82eT8nhgmzj /Q8+w2njMIGYz3MHVgM4nFzxzCLm0g4WWLrN5C+UkYc5SLUEOuFiu8BnwZABGJ3XqPh0 fj6umK6rJF/umw7CCRH4SG9eiAYRA5zPE0yA+OYEiXJHPLiro60EpcpDUo6inOeoVOjK mkgU/fnlsyvQH8xChdDB2l/OvmUQR6pzfgbrel2nSNkJKIltTbIs2H+UK/0n++/vEiQs 5Skg== X-Gm-Message-State: APuU4Z+caAg/dh+84Zpe5oZsXcvR1imN3StQ9yyTrobN8IN/IRoeTKNG 4HnSzPaiYSlXjOI+JeOe1OG/oEuXXznshyot9l9a65iORTQerT/RsRu66O/pdTI0AgYwzZVSkGm 7CcURtw== X-Gm-Gg: AYBFou1xgwcDlf/yRt2AtouCsgp8vbP57dCXkMb8p13Ojv58JYtwecmapjdVPxCK2Yw rb25HxJHwzPewY6I/6S17UdQDZuJXSbmf0zMuhkCE+T9SPs1U3AylwpbltUFu0mkiujfTuU2YKc 9FQn3KmTCJtIgYkTpWfjVfCIktPWi5sFOauGMfeuZSKPc3fT+D6CpcgAlAaerJrlJZnFWjS+x5P H5VsWv1pxkVzW8GwDEZSGx8+//mnW/Q0EksuAoJFJ3y2VR+3onjUNZrauA/9mKQufoHZVqzi0tf RTfM+xlZnr6OMOw/vVez516Us0ams8ayrd4yVcinHL9hv17um4lCnCZi/vyEkcrn+WEj+ie4wGF wR1asEJYV8XETcDZJyZJK5llBGF3tqGaA1SioBBGpHCXOHsd+6zBTgcQ+xU0ViwqIsZ5zkxDS6j HwTpgQ/9trw2wp7KPQ8hVTNnD3Sv5vQRZKIHmMZoIPF0SYDFxVjK408JCApKbsm+5CHU1KhMYph 0qUdpj/30CirV/PGer/rpzoCi8PKzQla+rvOVqLa8hxR5k+y4BbyGiKm/eajknUhCUX+cLc+ofd 1XZE3522l2QVBcjEuA2LxnWXUhK/k/QiVB8EGseXBePtuf13VroNHIyIdtpxJ/KgaA== X-Received: by 2002:a05:600c:3b9d:b0:4bb:5dbf:af06 with SMTP id 5b1f17b1804b1-4bb5dbfb103mr85932305e9.9.1794663294856; Sat, 14 Nov 2026 05:34:54 -0800 (PST) Received: from google.com (0.182.34.34.bc.googleusercontent.com. [34.34.182.0]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4bb4e2adf53sm237952865e9.15.2026.11.14.05.34.54 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 14 Nov 2026 05:34:54 -0800 (PST) Date: Sat, 14 Nov 2026 13:34:50 +0000 From: Vincent Donnefort To: sashiko-reviews@lists.linux.dev Cc: linux-trace-kernel@vger.kernel.org Subject: Re: [PATCH v1 3/4] ring-buffer: Order remote page commit with data and timestamp Message-ID: References: <20261113152729.837429-1-vdonnefort@google.com> <20261113152729.837429-4-vdonnefort@google.com> X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: On Fri, Nov 13, 2026 at 03:34:59PM +0000, sashiko-bot@kernel.org wrote: > Thank you for your contribution! Sashiko AI review found no new issues > in this patch, but noticed 1 related pre-existing issue it does not > introduce: > - [Critical] tracing: out-of-bounds write in simple_rb_reserve_next() > [1] > -- > > commit b0c88540d75d93c7a85149df8d188a1bfaa9a89e > Author: Vincent Donnefort > > ring-buffer: Order remote page commit with data and timestamp > > This commit adds memory barriers between page::commit, page::data, and > page::time_stamp for remote ring-buffers and defers updating read_stamp > until committed data is present on the reader page. > > > diff --git a/kernel/trace/simple_ring_buffer.c b/kernel/trace/simple_ring_buffer.c > > index 5f14ba152fba6..2dddaef638dc6 100644 > > --- a/kernel/trace/simple_ring_buffer.c > > +++ b/kernel/trace/simple_ring_buffer.c > > @@ -307,6 +307,11 @@ EXPORT_SYMBOL_GPL(simple_ring_buffer_reserve); > > */ > > void simple_ring_buffer_commit(struct simple_rb_per_cpu *cpu_buffer) > > { > > + /* > > + * Order page::data and page::time_stamp before page::commit. Paired > > + * with __rb_get_reader_page_from_remote(). > > + */ > > + smp_wmb(); > > local_set(&cpu_buffer->tail_page->page->commit, > > cpu_buffer->tail_page->write); > > [Severity: Critical] > This problem wasn't introduced by this patch, but can > simple_ring_buffer_reserve() return a pointer whose reservation overflows > tail->page->data [1]? > > In simple_rb_reserve_next(), when an event exceeds PAGE_SIZE - > BUF_PAGE_HDR_SIZE, simple_rb_move_tail() rotates to an empty page where > !tail->entries is true, and event_size is assigned to tail->write without > checking that it fits on a fresh page: > > kernel/trace/simple_ring_buffer.c:simple_rb_reserve_next() { > ... > if (unlikely(write > (PAGE_SIZE - BUF_PAGE_HDR_SIZE))) > tail = simple_rb_move_tail(cpu_buffer); > > if (!tail->entries) { > tail->page->time_stamp = timestamp; > time_delta = 0; > ts_ext_size = 0; > write = event_size; > prev_write = 0; > } > > tail->write = write; > ... > } > > Writing the caller's payload to the returned event pointer then writes past > the end of the page buffer and corrupts adjacent memory. > > [1] https://sashiko.dev/#/bug/linux-b2128783-1787-4f13-b863-090db5378e74 > > -- > Sashiko AI review · https://sashiko.dev/#/patchset/20261113152729.837429-1-vdonnefort@google.com?part=3 There's absolutely no existing event that is big enough to a ring buffer page! -- Vincent