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]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6011FC021B0 for ; Thu, 20 Feb 2025 07:02:58 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id B88244401CA; Thu, 20 Feb 2025 02:02:57 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id B38A44401AE; Thu, 20 Feb 2025 02:02:57 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 9FFDC4401CA; Thu, 20 Feb 2025 02:02:57 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0010.hostedemail.com [216.40.44.10]) by kanga.kvack.org (Postfix) with ESMTP id 81FE94401AE for ; Thu, 20 Feb 2025 02:02:57 -0500 (EST) Received: from smtpin29.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay08.hostedemail.com (Postfix) with ESMTP id 27979140ED0 for ; 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imf20.hostedemail.com; dkim=none; dmarc=pass (policy=none) header.from=arm.com; spf=pass (imf20.hostedemail.com: domain of anshuman.khandual@arm.com designates 217.140.110.172 as permitted sender) smtp.mailfrom=anshuman.khandual@arm.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1740034975; a=rsa-sha256; cv=none; b=tjADmLgBl/W13PS8o2sA89IhGh44Z0FZsVyAWdwKHq5GBsX2GurOZnD4019wrX5JS3+wco 0491o6g52/ZK0d/bd6RIkp+H5PTJvKtZhgSTeD44AnbThp9sQypqljgQS+JLCzHpBXl+QO VrXjlI7MnPmcBpSNTjcJdo6fKNROkVI= 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 A7BDC2008; Wed, 19 Feb 2025 23:03:12 -0800 (PST) Received: from [10.163.38.27] (unknown [10.163.38.27]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id DFBFD3F5A1; Wed, 19 Feb 2025 23:02:46 -0800 (PST) Message-ID: Date: Thu, 20 Feb 2025 12:32:37 +0530 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 08/14] mm/vmalloc: Warn on improper use of vunmap_range() To: Ryan Roberts , Catalin Marinas , Will Deacon , Pasha Tatashin , Andrew Morton , Uladzislau Rezki , Christoph Hellwig , David Hildenbrand , "Matthew Wilcox (Oracle)" , Mark Rutland , Alexandre Ghiti , Kevin Brodsky Cc: linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20250217140809.1702789-1-ryan.roberts@arm.com> <20250217140809.1702789-9-ryan.roberts@arm.com> Content-Language: en-US From: Anshuman Khandual In-Reply-To: <20250217140809.1702789-9-ryan.roberts@arm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspam-User: X-Stat-Signature: 3t19r3akufar7zpkj4s8kbn53eqqt1xw X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 712A71C0019 X-HE-Tag: 1740034975-285513 X-HE-Meta: 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 uppVDZD3 j734aeli7wgA68L478ziJS6FhUrQri7FSAfn8Dtq4qv/RAHoSw1mpo+Yl8C/alyz25loptzwjYAuIcR+9ByKlxmBrb/YW5XZGxB3/l36FM1TBZEkLGogni+/Vyn1hch9gyneSXgLUcAZds3yy7cLzbW8swVGNI7hhtj2EocujW2eFbZj6WjCQpg6Dw+eTjxroj//uXFpZfnNDzr55IU/PgLkUo2u8dKeiUGODC2zzifViIl4CyJpZuMu4dQ== 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: On 2/17/25 19:38, 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 subsequently call vunmap_range() on a > 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 just expected that callers will not do this. > > However, it would be useful to know if this happened in future; let's > add a warning to cover the eventuality. > > Signed-off-by: Ryan Roberts LGTM and stands on its own independent of the series here. Reviewed-by: Anshuman Khandual > --- > mm/vmalloc.c | 8 ++++++-- > 1 file changed, 6 insertions(+), 2 deletions(-) > > diff --git a/mm/vmalloc.c b/mm/vmalloc.c > index 61981ee1c9d2..a7e34e6936d2 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);