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Tue, 27 Oct 2026 16:27:41 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id BayYG/3Q4GpDBwAAD6G6ig (envelope-from ); Tue, 27 Oct 2026 16:27:41 +0000 Date: Tue, 27 Oct 2026 16:27:39 +0000 From: Pedro Falcato To: "David Hildenbrand (Arm)" 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 , Hugh Dickins , Pasha Tatashin , Pratyush Yadav , "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, Josef Bacik , stable@vger.kernel.org Subject: Re: [PATCH 35/46] mm: fix unmap_mapping_range() beyond 4 GiB on 32-bit Message-ID: References: <20261027-fixes_core-v1-0-6f74bec9a5bb@kernel.org> <20261027-fixes_core-v1-35-6f74bec9a5bb@kernel.org> X-Mailing-List: linux-arch@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20261027-fixes_core-v1-35-6f74bec9a5bb@kernel.org> X-Rspamd-Queue-Id: B670A21F29 X-Spam-Level: X-Rspamd-Server: rspamd2.dmz-prg2.suse.org X-Rspamd-Action: no action X-Spam-Flag: NO X-Spamd-Result: default: False [-12.01 / 50.00]; SUSE_INTERNAL_BYPASS(-9.00)[]; BAYES_HAM(-3.00)[100.00%]; SUSPICIOUS_RECIPS(1.50)[]; NEURAL_HAM_LONG(-1.00)[-1.000]; R_DKIM_ALLOW(-0.20)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; MX_GOOD(-0.01)[]; FREEMAIL_CC(0.00)[linux-foundation.org,cmpxchg.org,kernel.org,linux.dev,tencent.com,google.com,linux.alibaba.com,infradead.org,suse.com,soleen.com,suse.cz,nvidia.com,surriel.com,arm.com,intel.com,redhat.com,gmail.com,suse.de,huaweicloud.com,lge.com,gourry.net,sk.com,ziepe.ca,kvack.org,vger.kernel.org,lists.infradead.org,toxicpanda.com]; MIME_TRACE(0.00)[0:+]; ARC_NA(0.00)[]; RBL_SPAMHAUS_BLOCKED_OPENRESOLVER(0.00)[2a07:de40:b281:104:10:150:64:97:from]; URIBL_BLOCKED(0.00)[toxicpanda.com:email,suse.de:dkim,suse.de:email,imap1.dmz-prg2.suse.org:rdns,imap1.dmz-prg2.suse.org:helo]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; RCVD_TLS_ALL(0.00)[]; FROM_HAS_DN(0.00)[]; TO_DN_SOME(0.00)[]; TO_MATCH_ENVRCPT_SOME(0.00)[]; DNSWL_BLOCKED(0.00)[2a07:de40:b281:104:10:150:64:97:from,2a07:de40:b281:106:10:150:64:167:received]; RCVD_COUNT_TWO(0.00)[2]; FROM_EQ_ENVFROM(0.00)[]; DKIM_TRACE(0.00)[suse.de:+]; RCPT_COUNT_GT_50(0.00)[65]; TAGGED_RCPT(0.00)[]; RECEIVED_SPAMHAUS_BLOCKED_OPENRESOLVER(0.00)[2a07:de40:b281:106:10:150:64:167:received]; MISSING_XM_UA(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; DBL_BLOCKED_OPENRESOLVER(0.00)[imap1.dmz-prg2.suse.org:rdns,imap1.dmz-prg2.suse.org:helo,suse.de:dkim,suse.de:email,toxicpanda.com:email] X-Spam-Score: -12.01 On Tue, Oct 27, 2026 at 12:17:55AM +0100, David Hildenbrand (Arm) wrote: > From: Josef Bacik > > Commit 9eab0421fa94 ("mm: fix unmap_mapping_range high bits shift bug") > made holebegin and holelen unsigned before they are shifted, by casting > them to pgoff_t. That is an unsigned long: on a 32-bit kernel the cast > cuts off the upper half of the two loff_t values, so a hole which begins > at 4 GiB or beyond is taken for one in the first 4 GiB of the file. > > truncate_pagecache() passes the new size of the file and asks for private > COWed pages to be unmapped as well. If a file of 6 GiB is truncated to > 5 GiB, everything from 1 GiB on is unmapped, and what a process has > written to a private mapping of the range between 1 GiB and 5 GiB is > lost: it reads the contents of the file again. > > Where the range has an end, the wrong range is unmapped instead of the > right one. The page cache copes with that, as it unmaps every folio that > it removes. The callers which only have unmap_mapping_range() to get > rid of user mappings do not, for example drm_vma_node_unmap(), whose fake > offsets reach beyond 4 GiB on 32-bit, and revoke_iomem() with physical > addresses of more than 32 bits. > > Cast to u64 instead. Nothing changes for 64-bit kernels. > > Fix generated by an LLM and sent by Josef Bacik in private. > > Fixes: 9eab0421fa94 ("mm: fix unmap_mapping_range high bits shift bug") > Cc: stable@vger.kernel.org > Signed-off-by: Josef Bacik > Acked-by: Lorenzo Stoakes (ARM) > Signed-off-by: David Hildenbrand (Arm) Reviewed-by: Pedro Falcato -- Pedro