From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 8588CC2A06C for ; Sun, 4 Jan 2026 13:44:12 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id B59476B0092; Sun, 4 Jan 2026 08:44:11 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id B06EB6B0093; Sun, 4 Jan 2026 08:44:11 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id A08F96B0095; Sun, 4 Jan 2026 08:44:11 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id 8F0726B0092 for ; Sun, 4 Jan 2026 08:44:11 -0500 (EST) Received: from smtpin23.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay05.hostedemail.com (Postfix) with ESMTP id 18D045C864 for ; Sun, 4 Jan 2026 13:44:11 +0000 (UTC) X-FDA: 84294400302.23.20C7015 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by imf22.hostedemail.com (Postfix) with ESMTP id 1C2B5C0006 for ; Sun, 4 Jan 2026 13:44:08 +0000 (UTC) Authentication-Results: imf22.hostedemail.com; dkim=none; dmarc=pass (policy=none) header.from=arm.com; spf=pass (imf22.hostedemail.com: domain of ryan.roberts@arm.com designates 217.140.110.172 as permitted sender) smtp.mailfrom=ryan.roberts@arm.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1767534249; a=rsa-sha256; cv=none; b=X5etKiPvEifRwTM6duzMHwGqTqeu4zkFA2XWHM4iABptNdUhVTUwG0IBi2rWiI9LxKrE+h +Jo1T4Zs4bAMiimF67cBe6ODwq9586Csh/R93Y4Cos+tnK4kuFgnyKzUqqWYWsuLne9IIT MMpCi+O6zoGPa1jmbnAAtPzApteTzfg= ARC-Authentication-Results: i=1; imf22.hostedemail.com; dkim=none; dmarc=pass (policy=none) header.from=arm.com; spf=pass (imf22.hostedemail.com: domain of ryan.roberts@arm.com designates 217.140.110.172 as permitted sender) smtp.mailfrom=ryan.roberts@arm.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1767534249; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-transfer-encoding:content-transfer-encoding: in-reply-to:references; bh=31alRJjH9aMomaXC5Ty+m1cilsBmQIpUnm1Eg7pXAIE=; b=H7L9RdkI4at5+Qi+kD61NqIalKT4qHxIUMNxCvZTMXyTnQ3oE9hwQ0fXI3jfJ6u++uOnu9 lfIMcIw0dM/AlUiVRm+8KEIIvW2uOTKBi+H0ylrPJtFkoDfgRwjhUlBSw15WxUQjNdIwcp fMwwmoAGMZwzRcDo4wGECmw9YZh5G9o= Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 20FCF339; Sun, 4 Jan 2026 05:44:01 -0800 (PST) Received: from e125769.cambridge.arm.com (e125769.cambridge.arm.com [10.1.196.27]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id D41783F5A1; Sun, 4 Jan 2026 05:44:06 -0800 (PST) From: Ryan Roberts To: Alexander Potapenko , Marco Elver , Dmitry Vyukov , Andrew Morton Cc: Ryan Roberts , kasan-dev@googlegroups.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: [PATCH v1] mm: kmsan: Fix poisoning of high-order non-compound pages Date: Sun, 4 Jan 2026 13:43:47 +0000 Message-ID: <20260104134348.3544298-1-ryan.roberts@arm.com> X-Mailer: git-send-email 2.43.0 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Queue-Id: 1C2B5C0006 X-Rspamd-Server: rspam04 X-Stat-Signature: wwdncfup6izg7rusm9jwx4cjsxwwd9wa X-HE-Tag: 1767534248-802544 X-HE-Meta: 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 3zRRncdl Ng2lyAIeL8+LPzAT2TXWIZ8uzmj10V7oePOXEm/++8DaT3AXrLUot9lGIeZVACT9FmS5C2sEpCA72d1vicxCPvFAyK312AOfk2w7li8C8VKymPuX7q8sPAsqiVdj8F9j3G413167eIKLhLmFKv+7f8koFXaVE5Hwu4+VafBR5Bdi1+2M= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: kmsan_free_page() is called by the page allocator's free_pages_prepare() during page freeing. It's job is to poison all the memory covered by the page. It can be called with an order-0 page, a compound high-order page or a non-compound high-order page. But page_size() only works for order-0 and compound pages. For a non-compound high-order page it will incorrectly return PAGE_SIZE. The implication is that the tail pages of a high-order non-compound page do not get poisoned at free, so any invalid access while they are free could go unnoticed. It looks like the pages will be poisoned again at allocaiton time, so that would bookend the window. Fix this by using the order parameter to calculate the size. Fixes: b073d7f8aee4 ("mm: kmsan: maintain KMSAN metadata for page operations") Cc: stable@vger.kernel.org Signed-off-by: Ryan Roberts --- Hi, I noticed this during code review, so perhaps I've just misunderstood the intent of the code. I don't have the means to compile and run on x86 with KMSAN enabled though, so punting this out hoping someone might be able to validate/test. I guess there is a small chance this could lead to KMSAN finding some new issues? Applies against today's mm-unstable (344d3580dacd). Thanks, Ryan mm/kmsan/shadow.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/mm/kmsan/shadow.c b/mm/kmsan/shadow.c index e7f554a31bb4..9e1c5f2b7a41 100644 --- a/mm/kmsan/shadow.c +++ b/mm/kmsan/shadow.c @@ -207,7 +207,7 @@ void kmsan_free_page(struct page *page, unsigned int order) if (!kmsan_enabled || kmsan_in_runtime()) return; kmsan_enter_runtime(); - kmsan_internal_poison_memory(page_address(page), page_size(page), + kmsan_internal_poison_memory(page_address(page), PAGE_SIZE << order, GFP_KERNEL & ~(__GFP_RECLAIM), KMSAN_POISON_CHECK | KMSAN_POISON_FREE); kmsan_leave_runtime(); -- 2.43.0