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Fri, 8 Aug 2025 17:17:25 +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 J+GCKSUxlmgrYQAAD6G6ig (envelope-from ); Fri, 08 Aug 2025 17:17:25 +0000 Message-ID: Date: Fri, 8 Aug 2025 19:17:25 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 6.17 2/3] mm/mremap: catch invalid multi VMA moves earlier Content-Language: en-US To: Lorenzo Stoakes , Andrew Morton Cc: "Liam R . Howlett" , Jann Horn , Pedro Falcato , David Hildenbrand , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <2b5aad5681573be85b5b8fac61399af6fb6b68b6.1754218667.git.lorenzo.stoakes@oracle.com> From: Vlastimil Babka Autocrypt: addr=vbabka@suse.cz; keydata= xsFNBFZdmxYBEADsw/SiUSjB0dM+vSh95UkgcHjzEVBlby/Fg+g42O7LAEkCYXi/vvq31JTB KxRWDHX0R2tgpFDXHnzZcQywawu8eSq0LxzxFNYMvtB7sV1pxYwej2qx9B75qW2plBs+7+YB 87tMFA+u+L4Z5xAzIimfLD5EKC56kJ1CsXlM8S/LHcmdD9Ctkn3trYDNnat0eoAcfPIP2OZ+ 9oe9IF/R28zmh0ifLXyJQQz5ofdj4bPf8ecEW0rhcqHfTD8k4yK0xxt3xW+6Exqp9n9bydiy tcSAw/TahjW6yrA+6JhSBv1v2tIm+itQc073zjSX8OFL51qQVzRFr7H2UQG33lw2QrvHRXqD Ot7ViKam7v0Ho9wEWiQOOZlHItOOXFphWb2yq3nzrKe45oWoSgkxKb97MVsQ+q2SYjJRBBH4 8qKhphADYxkIP6yut/eaj9ImvRUZZRi0DTc8xfnvHGTjKbJzC2xpFcY0DQbZzuwsIZ8OPJCc LM4S7mT25NE5kUTG/TKQCk922vRdGVMoLA7dIQrgXnRXtyT61sg8PG4wcfOnuWf8577aXP1x 6mzw3/jh3F+oSBHb/GcLC7mvWreJifUL2gEdssGfXhGWBo6zLS3qhgtwjay0Jl+kza1lo+Cv BB2T79D4WGdDuVa4eOrQ02TxqGN7G0Biz5ZLRSFzQSQwLn8fbwARAQABzSBWbGFzdGltaWwg QmFia2EgPHZiYWJrYUBzdXNlLmN6PsLBlAQTAQoAPgIbAwULCQgHAwUVCgkICwUWAgMBAAIe AQIXgBYhBKlA1DSZLC6OmRA9UCJPp+fMgqZkBQJnyBr8BQka0IFQAAoJECJPp+fMgqZkqmMQ AIbGN95ptUMUvo6aAdhxaOCHXp1DfIBuIOK/zpx8ylY4pOwu3GRe4dQ8u4XS9gaZ96Gj4bC+ jwWcSmn+TjtKW3rH1dRKopvC07tSJIGGVyw7ieV/5cbFffA8NL0ILowzVg8w1ipnz1VTkWDr 2zcfslxJsJ6vhXw5/npcY0ldeC1E8f6UUoa4eyoskd70vO0wOAoGd02ZkJoox3F5ODM0kjHu Y97VLOa3GG66lh+ZEelVZEujHfKceCw9G3PMvEzyLFbXvSOigZQMdKzQ8D/OChwqig8wFBmV QCPS4yDdmZP3oeDHRjJ9jvMUKoYODiNKsl2F+xXwyRM2qoKRqFlhCn4usVd1+wmv9iLV8nPs 2Db1ZIa49fJet3Sk3PN4bV1rAPuWvtbuTBN39Q/6MgkLTYHb84HyFKw14Rqe5YorrBLbF3rl M51Dpf6Egu1yTJDHCTEwePWug4XI11FT8lK0LNnHNpbhTCYRjX73iWOnFraJNcURld1jL1nV r/LRD+/e2gNtSTPK0Qkon6HcOBZnxRoqtazTU6YQRmGlT0v+rukj/cn5sToYibWLn+RoV1CE Qj6tApOiHBkpEsCzHGu+iDQ1WT0Idtdynst738f/uCeCMkdRu4WMZjteQaqvARFwCy3P/jpK uvzMtves5HvZw33ZwOtMCgbpce00DaET4y/UzsBNBFsZNTUBCACfQfpSsWJZyi+SHoRdVyX5 J6rI7okc4+b571a7RXD5UhS9dlVRVVAtrU9ANSLqPTQKGVxHrqD39XSw8hxK61pw8p90pg4G /N3iuWEvyt+t0SxDDkClnGsDyRhlUyEWYFEoBrrCizbmahOUwqkJbNMfzj5Y7n7OIJOxNRkB IBOjPdF26dMP69BwePQao1M8Acrrex9sAHYjQGyVmReRjVEtv9iG4DoTsnIR3amKVk6si4Ea X/mrapJqSCcBUVYUFH8M7bsm4CSxier5ofy8jTEa/CfvkqpKThTMCQPNZKY7hke5qEq1CBk2 wxhX48ZrJEFf1v3NuV3OimgsF2odzieNABEBAAHCwXwEGAEKACYCGwwWIQSpQNQ0mSwujpkQ PVAiT6fnzIKmZAUCZ8gcVAUJFhTonwAKCRAiT6fnzIKmZLY8D/9uo3Ut9yi2YCuASWxr7QQZ lJCViArjymbxYB5NdOeC50/0gnhK4pgdHlE2MdwF6o34x7TPFGpjNFvycZqccSQPJ/gibwNA zx3q9vJT4Vw+YbiyS53iSBLXMweeVV1Jd9IjAoL+EqB0cbxoFXvnjkvP1foiiF5r73jCd4PR rD+GoX5BZ7AZmFYmuJYBm28STM2NA6LhT0X+2su16f/HtummENKcMwom0hNu3MBNPUOrujtW khQrWcJNAAsy4yMoJ2Lw51T/5X5Hc7jQ9da9fyqu+phqlVtn70qpPvgWy4HRhr25fCAEXZDp xG4RNmTm+pqorHOqhBkI7wA7P/nyPo7ZEc3L+ZkQ37u0nlOyrjbNUniPGxPxv1imVq8IyycG AN5FaFxtiELK22gvudghLJaDiRBhn8/AhXc642/Z/yIpizE2xG4KU4AXzb6C+o7LX/WmmsWP Ly6jamSg6tvrdo4/e87lUedEqCtrp2o1xpn5zongf6cQkaLZKQcBQnPmgHO5OG8+50u88D9I rywqgzTUhHFKKF6/9L/lYtrNcHU8Z6Y4Ju/MLUiNYkmtrGIMnkjKCiRqlRrZE/v5YFHbayRD dJKXobXTtCBYpLJM4ZYRpGZXne/FAtWNe4KbNJJqxMvrTOrnIatPj8NhBVI0RSJRsbilh6TE m6M14QORSWTLRg== In-Reply-To: <2b5aad5681573be85b5b8fac61399af6fb6b68b6.1754218667.git.lorenzo.stoakes@oracle.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Action: no action X-Stat-Signature: ctwujwej81n8ptejjw6eh8e4r6m3d1rq X-Rspamd-Queue-Id: 9F4871C000B X-Rspamd-Server: rspam10 X-Rspam-User: X-HE-Tag: 1754673447-981922 X-HE-Meta: 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 5OoWO4FQ IyJYMQAyRrbG4wJnzoLbmXNL1CUBwFRPU9+x6WN8MDTtpC71dH4oAhT8lqEdTwIIZU/E/rm1jBm150A0orJbWHy8p9DzI4qwPX5q+4OsWbKhCO2r3Epeu8VDeSO6xLRfh+ih+UYVVwmnKmZVK6NQxh3D+KvYbVhTpcs3WPHyH56jnNWP+P9MvMHK/erIonzFjiKHMQESOzQJdUxf2HzlIMshGJnHHBI31uRboUwAmZBYYJz3//xkQHW1kGx0EbrweqPOhrUbFYuB0612vTmp851hbHz+zCYN+/64JsruLN5vaAlHW+1ac7Vj4qw== 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 8/3/25 13:11, Lorenzo Stoakes wrote: > In remap_move() we must account for both a single VMA case, where we are > permitted to move a single VMA regardless of multi-VMA move eligiblity, and > multiple VMAs which, of course, must be eligible for such an operation. > > We determine this via vma_multi_allowed(). > > Currently, if the first VMA is not eligible, but others are, we will move > the first then return an error. This is not ideal, as we are performing an > operation which we don't need to do which has an impact on the memory > mapping. > > We can very easily determine if this is a multi VMA move prior to the move > of the first VMA, by checking vma->vm_end vs. the specified end address. > > Therefore this patch does so, and as a result eliminates unnecessary logic > around tracking whether the first VMA was permitted or not. > > This is most useful for cases where a user attempts to erroneously move > mutliple VMAs which are not eligible for non-transient reasons - for > instance, UFFD-armed VMAs, or file-backed VMAs backed by a file system or > driver which specifies a custom f_op->get_unmapped_area. > > In the less likely instance of a failure due to transient issues such as > out of memory or mapping limits being hit, the issue is already likely > fatal and so the fact the operation may be partially complete is > acceptable. > > Signed-off-by: Lorenzo Stoakes With the updated commit log, Reviewed-by: Vlastimil Babka