From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-179.mta0.migadu.com (out-179.mta0.migadu.com [91.218.175.179]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 70586279333 for ; Tue, 1 Jul 2025 14:15:57 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.179 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1751379359; cv=none; b=ktBkVUvPIDHddmJuq/KFI6UM74AxKpLGncS+yxUTzZOPV2IIeEpXJhZYJT9uayuc9ivb1dWWeD11GiFes+gDuW1ThN6h4vpCaMYr1W8t9HRZODFxeS8CyD34FhKGvrOSih5DTfqOF/66XmkjROhSfyY4KLzbLNzYnpTHuaQBkgs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1751379359; c=relaxed/simple; bh=GJP7Xa/2ev6INSY+ZGt6Xkxf+i9v+ytOpFJCc009TJU=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=LOe0w9UcgIizyu4IRV0R3+JtR5caEwh3HglBVCjK/u9kFxA4F9pdmp8HXPWbp5L0WRm7+qRIxvOQGkz03SH7hjPwoDSnHqXBIFLWP5UCpfuSBScNF2yzFRmRuQKQBfXMIKSbm6Ilz9rubBzITZ45BZXIjc03c4/DXrv7AswXN6Y= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=rwerCEIA; arc=none smtp.client-ip=91.218.175.179 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="rwerCEIA" Message-ID: <0a96ce38-163e-4566-b666-b074bd82c75a@linux.dev> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1751379345; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=CbwuurgTDZ+BaZBkyMf18Zq8IPSFXnHhnJxSaiCg6gM=; b=rwerCEIAJb39fesv0EF8pOU/ob/YjbEMZ4v0sWNU2xHq0OxhcXljvBD2n5VH+/cKs1v5qS GEq/jLdRP4QJopKUgt18uPvXuzdrO+Gw3KUgU3FysEGlvfuCeVyGbBJd7yShJDeT+1GSXC 8ObslLOB3iUPbBIQR6Kfi8w4SylwS7k= Date: Tue, 1 Jul 2025 22:15:27 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Subject: Re: [PATCH v3 1/1] mm/rmap: fix potential out-of-bounds page table access during batched unmap Content-Language: en-US To: David Hildenbrand , akpm@linux-foundation.org, 21cnbao@gmail.com Cc: baolin.wang@linux.alibaba.com, chrisl@kernel.org, kasong@tencent.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-riscv@lists.infradead.org, lorenzo.stoakes@oracle.com, ryan.roberts@arm.com, v-songbaohua@oppo.com, x86@kernel.org, huang.ying.caritas@gmail.com, zhengtangquan@oppo.com, riel@surriel.com, Liam.Howlett@oracle.com, vbabka@suse.cz, harry.yoo@oracle.com, mingzhe.yang@ly.com, stable@vger.kernel.org, Barry Song , Lance Yang References: <20250630011305.23754-1-lance.yang@linux.dev> <330f29ee-ba55-4ae6-a695-ddaba58d5cb8@redhat.com> X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Lance Yang In-Reply-To: <330f29ee-ba55-4ae6-a695-ddaba58d5cb8@redhat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Migadu-Flow: FLOW_OUT On 2025/7/1 22:03, David Hildenbrand wrote: > On 30.06.25 03:13, Lance Yang wrote: >> From: Lance Yang >> >> As pointed out by David[1], the batched unmap logic in try_to_unmap_one() >> may read past the end of a PTE table when a large folio's PTE mappings >> are not fully contained within a single page table. >> >> While this scenario might be rare, an issue triggerable from userspace >> must >> be fixed regardless of its likelihood. This patch fixes the out-of-bounds >> access by refactoring the logic into a new helper, >> folio_unmap_pte_batch(). >> >> The new helper correctly calculates the safe batch size by capping the >> scan >> at both the VMA and PMD boundaries. To simplify the code, it also >> supports >> partial batching (i.e., any number of pages from 1 up to the calculated >> safe maximum), as there is no strong reason to special-case for fully >> mapped folios. >> >> [1] https://lore.kernel.org/linux-mm/ >> a694398c-9f03-4737-81b9-7e49c857fcbe@redhat.com >> >> Fixes: 354dffd29575 ("mm: support batched unmap for lazyfree large >> folios during reclamation") >> Cc: >> Acked-by: Barry Song >> Suggested-by: David Hildenbrand > > Realized this now: This should probably be a "Reported-by:" with the > "Closes:" and and a link to my mail. Got it. Both tags (Reported-by/Closes) will be in the next commit ;)