From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.subspace.kernel.org (Postfix) with ESMTP id A34B3606A31A for ; Tue, 27 Oct 2026 19:23:13 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=ftRU37dy Received: by kanga.kvack.org (Postfix) id A977F6B08B7; Tue, 27 Oct 2026 15:23:12 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id A6EC86B08B9; Tue, 27 Oct 2026 15:23:12 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 934CE6B08BA; Tue, 27 Oct 2026 15:23:12 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id 62EA36B08B7 for ; Tue, 27 Oct 2026 15:23:12 -0400 (EDT) Received: from smtpin10.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay06.hostedemail.com (Postfix) with ESMTP id 0A487A8859 for ; Tue, 27 Oct 2026 19:23:12 +0000 (UTC) X-FDA: 85369379424.10.C2AC020 Received: from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254]) by imf10.hostedemail.com (Postfix) with ESMTP id 51308C0003 for ; Tue, 27 Oct 2026 19:23:10 +0000 (UTC) Authentication-Results: imf10.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=ftRU37dy; spf=pass (imf10.hostedemail.com: domain of david@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=david@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1793128990; 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-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=HoOcwxnYW5BPsnbBpyOUUjSJrZpAEuBUDQ6Rytj43SI=; b=dbwI+R4Y+uyQ4QNlgaAdSurYQlPE9T34DMicurrLcP9RhWKlpyH15oj8eFK4MVJ9B+SNiu 1PQzMX9+8LSUDdnipWJGEkpqY9/38dTNKehzU1S01NBSqAAFRsTjjRz8Lf58akhSVz0yKq zgGFgqA5g6d3B78WS6X4tEf3K0YsIuQ= ARC-Authentication-Results: i=1; imf10.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=ftRU37dy; spf=pass (imf10.hostedemail.com: domain of david@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=david@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1793128990; b=eRCyTTktaCifUjo2HPJbCY62qYXjB2qxA/OYpb41i94Q6lAGNs2Has3znvY6rSC/1dQBX+ PW9QcWQ/8CRYSknENti+txig3gEO6rncfSDm4iqKHHzOmAOAMgDLsgF0ndqSefWoEGuYK+ Zsw56X1SpXv21W0EP7vlbIoUYutAIBU= Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by tor.source.kernel.org (Postfix) with ESMTP id CD91E6022E; Tue, 27 Oct 2026 19:23:09 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 331471F031E6; Tue, 27 Oct 2026 19:22:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793128989; bh=HoOcwxnYW5BPsnbBpyOUUjSJrZpAEuBUDQ6Rytj43SI=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=ftRU37dyB4p0fpCveWi8u9OzVVMH+c9jVXZBnjJEcbX+3eUtHh0Bpvj0EPoUXVaPi 0QIZG6aMCRRp9b8cz1jyaC4I/RPv5oyxP0gLO6UnDAB0wFu8xZJKIBLAV8TY4tp2Zs V90tZ5gdhOHNZIuy4O8LU/EauDhEGQ1e41/XKUoUv+VeND2ArLOaAradJIZSY1HXf1 4HUN70NN0Glr6awt8YHNGO19R2ozNFjPj7mGG/v7TegGd0qz55IDN87LZJ/bb9e51c XNnTusUt2bSy/KdE3hQfe6e0wG0LfmdjZ9rOOnLn6PNHQxl3T0uu0eA167PkncXzMF vWwdNA1FTwpXg== Message-ID: Date: Tue, 27 Oct 2026 20:20:43 +0100 X-Archived-By: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 20/46] mm/gup: fix clearing folios in memfd_pin_folios() To: Pratyush Yadav Cc: Andrew Morton , Johannes Weiner , Michal Hocko , Qi Zheng , Shakeel Butt , Lorenzo Stoakes , Kairui Song , Barry Song , Axel Rasmussen , Yuanchu Xie , Wei Xu , Baoquan He , Baolin Wang , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Kees Cook , Peter Zijlstra , Jann Horn , Pedro Falcato , Hugh Dickins , Pasha Tatashin , "Matthew Wilcox (Oracle)" , Jan Kara , Zi Yan , Lance Yang , Rik van Riel , Harry Yoo , Alistair Popple , Nico Pache , Ryan Roberts , Dev Jain , Usama Arif , Kiryl Shutsemau , Matthew Brost , John Hubbard , Peter Xu , Will Deacon , "Aneesh Kumar K.V" , Nick Piggin , Oscar Salvador , Minchan Kim , Muchun Song , Xu Xin , Chengming Zhou , Chris Li , Kemeng Shi , Nhat Pham , Youngjun Park , Gregory Price , Joshua Hahn , Rakie Kim , Ying Huang , Jason Gunthorpe , linux-mm@kvack.org, linux-kernel@vger.kernel.org, kexec@lists.infradead.org, linux-fsdevel@vger.kernel.org, linux-arch@vger.kernel.org, linux-cxl@vger.kernel.org, Chris Mason , stable@vger.kernel.org References: <20261027-fixes_core-v1-0-6f74bec9a5bb@kernel.org> <20261027-fixes_core-v1-20-6f74bec9a5bb@kernel.org> <2vxzbj8fp4sn.fsf@kernel.org> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 51308C0003 X-Stat-Signature: skpa3k8zgwety3u37cggmtru7f5fjxqt X-Rspam-User: X-Spam-Status: No, score=-17.6 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_PASS, SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=4.0.1 X-HE-Tag: 1793128990-228129 X-HE-Meta: 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 T9ynBcaz RiTvYG923+jCS5z8BZCsYKx5BIA4GrK33kaxceQUytdZnyK5JvxWJoY5h4NzumhVDm4lTOYIPrUY8yylbaZgDJvDHf9wxS+E4sa95RWq0R5fpZMg/51OLQeEd3LsSjUJv4Pheig+2qUlKbmrFMzLg+BptZETgB6sMKcsFIz9/eC3hOGlV/9rdK6JuR57XovQ+AnWdwPdQmnm0Kzw9ckZPvVS+QwkHZCDmM2fbrPjMhTScYRPCWEsTlMwnGwDoEHhTHuBekc971uzocsGkXnVGx0DrF+u5Vc7EF1u4fYkfpxBIV6J1kmhJYD8e6TW9nYkL5X7lDh2XPASyTvFf89c0OHxKMMJQzWnohCHeD2zGANUav3lBC++MOf923QYy5nUupdnSdBMoIXKx2MC4/FXgfq/VRg== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 On 10/27/26 16:00, Pratyush Yadav wrote: > On Tue, Oct 27 2026, David Hildenbrand (Arm) wrote: > >> From: Chris Mason >> >> memfd_pin_folios() pins folios obtained directly from the page cache >> without checking whether they are uptodate. However, shmem fallocate() >> can leave newly allocated folios uncleared and not uptodate. Callers >> such as udmabuf can then expose uninitialized memory to userspace. >> >> Clear non-uptodate folios and mark them uptodate under the folio lock >> before returning them to the caller. >> >> Fix generated by an LLM and sent by Chris Mason in private. >> >> Fixes: 89c1905d9c14 ("mm/gup: introduce memfd_pin_folios() for pinning memfd folios") >> Cc: stable@vger.kernel.org >> Signed-off-by: Chris Mason >> [ david: simplify description and comment ] >> Signed-off-by: David Hildenbrand (Arm) >> --- >> mm/gup.c | 14 ++++++++++++++ >> 1 file changed, 14 insertions(+) >> >> diff --git a/mm/gup.c b/mm/gup.c >> index efc9aa2654625..47e7ae152cdf1 100644 >> --- a/mm/gup.c >> +++ b/mm/gup.c >> @@ -3516,6 +3516,20 @@ long memfd_pin_folios(struct file *memfd, loff_t start, loff_t end, >> goto err; >> } >> >> + /* >> + * fallocate() can leave folios in the >> + * page cache that were never cleared. >> + */ >> + if (!folio_test_uptodate(folio)) { >> + folio_lock(folio); >> + if (!folio_test_uptodate(folio)) { >> + folio_zero_range(folio, 0, folio_size(folio)); >> + flush_dcache_folio(folio); >> + folio_mark_uptodate(folio); >> + } >> + folio_unlock(folio); >> + } >> + > > Nit: this logic is repeated in a couple places in shmem.c and in > memfd_luo.c. Perhaps it deserves a helper? > > Anyway, sounds like an important fix so don't make my nitpick stop you > from landing this if you don't want to bother. Thanks! yeah, I had the same thought when trying to improve this. We should have an easier way to just not hand out unzeroed folios outside of shmem core functions in the first place ... -- Cheers, David