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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id AEF2DC02192 for ; Fri, 7 Feb 2025 08:53:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: Content-Type:In-Reply-To:From:References:Cc:To:Subject:MIME-Version:Date: Message-ID:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=46Vyq7A+e4k207UahJM24hikJyL1LFx+TFhTjPhwd1A=; b=Am4GoJV7NBDgWMnSM4jPH+3tZ9 JQSc8mNRHZpjxtKI8IjI/d0YKz0E1aO7UVuGG/ph6yZmFqLZ1+t9plxEmManQ33MZlVLnSYDVbOYJ VZLW2dyhz3kYTVsll5ii0bvO0M064oA5gBjqxdURezznk49eL409NMFu7s3FE65Zr8WS7kspiS5rE YosSVOOy1kyzxV9XaGQSSFq40rZ6TXmz6R0wVog8qX4BoPlPkSL6YNlK9sIqpkZ/edTvSo9x2hA6S wVptZfZFBh5loDRulnqUhp0oMxa1JQJf4p3aa3/Dh8VLrPU5QULhfPN/wU9e03432KUg+i0N6fUJL vWVLpkrg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98 #2 (Red Hat Linux)) id 1tgK7H-00000008tGW-19Vb; Fri, 07 Feb 2025 08:53:39 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.98 #2 (Red Hat Linux)) id 1tgJvW-00000008rGO-10hR for linux-arm-kernel@lists.infradead.org; Fri, 07 Feb 2025 08:41:31 +0000 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 602831063; Fri, 7 Feb 2025 00:41:52 -0800 (PST) Received: from [10.162.16.89] (a077893.blr.arm.com [10.162.16.89]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 68CBC3F5A1; Fri, 7 Feb 2025 00:41:24 -0800 (PST) Message-ID: <3bbae070-1ae3-4f5d-86ab-b3221425a1cb@arm.com> Date: Fri, 7 Feb 2025 14:11:21 +0530 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v1 10/16] mm/vmalloc: Warn on improper use of vunmap_range() To: Ryan Roberts , Catalin Marinas , Will Deacon , Muchun Song , Pasha Tatashin , Andrew Morton , Uladzislau Rezki , Christoph Hellwig , Mark Rutland , Ard Biesheuvel , Dev Jain , Alexandre Ghiti , Steve Capper , Kevin Brodsky Cc: linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20250205151003.88959-1-ryan.roberts@arm.com> <20250205151003.88959-11-ryan.roberts@arm.com> Content-Language: en-US From: Anshuman Khandual In-Reply-To: <20250205151003.88959-11-ryan.roberts@arm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250207_004130_321558_1E14D5BB X-CRM114-Status: GOOD ( 20.36 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 2/5/25 20:39, Ryan Roberts wrote: > A call to vmalloc_huge() may cause memory blocks to be mapped at pmd or > pud level. But it is possible to subsquently call vunmap_range() on a s/subsquently/subsequently > sub-range of the mapped memory, which partially overlaps a pmd or pud. > In this case, vmalloc unmaps the entire pmd or pud so that the > no-overlapping portion is also unmapped. Clearly that would have a bad > outcome, but it's not something that any callers do today as far as I > can tell. So I guess it's jsut expected that callers will not do this. s/jsut/just > > However, it would be useful to know if this happened in future; let's > add a warning to cover the eventuality. This is a reasonable check to prevent bad outcomes later. > > Signed-off-by: Ryan Roberts > --- > mm/vmalloc.c | 8 ++++++-- > 1 file changed, 6 insertions(+), 2 deletions(-) > > diff --git a/mm/vmalloc.c b/mm/vmalloc.c > index a6e7acebe9ad..fcdf67d5177a 100644 > --- a/mm/vmalloc.c > +++ b/mm/vmalloc.c > @@ -374,8 +374,10 @@ static void vunmap_pmd_range(pud_t *pud, unsigned long addr, unsigned long end, > if (cleared || pmd_bad(*pmd)) > *mask |= PGTBL_PMD_MODIFIED; > > - if (cleared) > + if (cleared) { > + WARN_ON(next - addr < PMD_SIZE); > continue; > + } > if (pmd_none_or_clear_bad(pmd)) > continue; > vunmap_pte_range(pmd, addr, next, mask); > @@ -399,8 +401,10 @@ static void vunmap_pud_range(p4d_t *p4d, unsigned long addr, unsigned long end, > if (cleared || pud_bad(*pud)) > *mask |= PGTBL_PUD_MODIFIED; > > - if (cleared) > + if (cleared) { > + WARN_ON(next - addr < PUD_SIZE); > continue; > + } > if (pud_none_or_clear_bad(pud)) > continue; > vunmap_pmd_range(pud, addr, next, mask); Why not also include such checks in vunmap_p4d_range() and __vunmap_range_noflush() for corresponding P4D and PGD levels as well ?