From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 36F5E3BF694 for ; Fri, 29 May 2026 11:31:46 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780054308; cv=none; b=ugWI7U/7BUePejCMsMZtlr0n8tX0M57wk2qabPBfR90vS/Macnno+n8Q+LLmE2ROYCBhVAnUfA6Khyu1g5K/rZJtnPoL0yFnSmc7BaYf4LkWobi951qpEruGbvwtUvki2KV0fIMaYn8PEMty6m7FXSnSevqf8/3kA7oe76jLTzk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780054308; c=relaxed/simple; bh=7wNWS9G2isk3ay7W/OlQsP9pBnm4LokiIAH66a7qO6k=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=mv/Zk/YosNihbvSGIvNYEV2gsx5kJBzM+JiwiKYmwnEvSl/+cZDgL0TvwYU4a3gmI8Zfh5+jSxwMgQ5RjlTOrC3cOaS3bQBFBqMxg+/1pxmCXbeTTO7vseqjcqQ9v3B1dwXCerhhPQOTVXXLw9AGRbwxFtnNDa4e62EWB23M5vY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b=gb4Wtsl9; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b="gb4Wtsl9" 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 7B0BB1BB2; Fri, 29 May 2026 04:31:41 -0700 (PDT) Received: from [10.164.19.8] (unknown [10.164.19.8]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id A83F63F905; Fri, 29 May 2026 04:31:38 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1780054306; bh=7wNWS9G2isk3ay7W/OlQsP9pBnm4LokiIAH66a7qO6k=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=gb4Wtsl9lGfCjyuj/e2onZlS+uOdUkNQtWYAIb8fbhFsFZtGyzaDL79o6EPgHmmRX 5xCSAbBbUavIpajduL1Zruct0EJQ7KgmjSJkP3P21sJiYMYu/CqBCrSWbduj5VTDzE VCJRaYauoDV8y6d1e22E5SEbL+DeWa2fUOO/T0Wk= Message-ID: Date: Fri, 29 May 2026 17:01:35 +0530 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 04/13] mm/huge_memory: move softleaf_to_folio() inside migration branch To: Usama Arif , Andrew Morton , david@kernel.org, chrisl@kernel.org, kasong@tencent.com, ljs@kernel.org, ziy@nvidia.com Cc: bhe@redhat.com, willy@infradead.org, youngjun.park@lge.com, hannes@cmpxchg.org, riel@surriel.com, shakeel.butt@linux.dev, alex@ghiti.fr, kas@kernel.org, baohua@kernel.org, baolin.wang@linux.alibaba.com, npache@redhat.com, Liam.Howlett@oracle.com, ryan.roberts@arm.com, Vlastimil Babka , lance.yang@linux.dev, linux-kernel@vger.kernel.org, nphamcs@gmail.com, shikemeng@huaweicloud.com, kernel-team@meta.com References: <20260427100553.2754667-1-usama.arif@linux.dev> <20260427100553.2754667-5-usama.arif@linux.dev> Content-Language: en-US From: Dev Jain In-Reply-To: <20260427100553.2754667-5-usama.arif@linux.dev> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 27/04/26 3:31 pm, Usama Arif wrote: > change_non_present_huge_pmd() calls softleaf_to_folio() unconditionally > at the top of the function. softleaf_to_folio() extracts a PFN from > the entry and converts it to a folio pointer, which is only meaningful > for migration and device_private entries that encode a real PFN. > > A swap entry encodes a swap offset instead, so softleaf_to_folio() > would produce a bogus pointer and crash on mprotect() when a PMD swap > entry is present. > > Move the call into the migration_write branch where the folio is > actually used, so the function is safe for any non-present PMD type. > > Signed-off-by: Usama Arif > --- Reviewed-by: Dev Jain > mm/huge_memory.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/mm/huge_memory.c b/mm/huge_memory.c > index 49da0746b8ca..d82a19b5e276 100644 > --- a/mm/huge_memory.c > +++ b/mm/huge_memory.c > @@ -2619,11 +2619,12 @@ static void change_non_present_huge_pmd(struct mm_struct *mm, > bool uffd_wp_resolve) > { > softleaf_t entry = softleaf_from_pmd(*pmd); > - const struct folio *folio = softleaf_to_folio(entry); > pmd_t newpmd; > > VM_WARN_ON(!pmd_is_valid_softleaf(*pmd)); > if (softleaf_is_migration_write(entry)) { > + const struct folio *folio = softleaf_to_folio(entry); > + > /* > * A protection check is difficult so > * just be safe and disable write