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Thu, 16 Oct 2025 13:18:37 +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 g/LWDq3w8GhyOgAAD6G6ig (envelope-from ); Thu, 16 Oct 2025 13:18:37 +0000 Message-ID: Date: Thu, 16 Oct 2025 15:18:36 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v5] slab: reset obj_ext when it is not actually valid during freeing Content-Language: en-US To: Harry Yoo Cc: Suren Baghdasaryan , Hao Ge , Andrew Morton , Christoph Lameter , David Rientjes , Roman Gushchin , Alexei Starovoitov , Shakeel Butt , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Hao Ge References: <20251015141642.700170-1-hao.ge@linux.dev> <0928dcc7-a4e0-4641-9381-6adf2ad30493@suse.cz> 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: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Action: no action X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 3B9E3A000E X-Stat-Signature: 5ohoztqagjssp4d5tjuswsnf47unjdzr X-Rspam-User: X-HE-Tag: 1760620718-107011 X-HE-Meta: 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 0LIWtYfD myaiFb6SG8+lCW6D+UtxJO46zAKInnFGT8PuvGya/XqRQFk94v+PwZUJ6bbFVBnrXLEr+he9n+ZN8xLrsT+/0cj9KzX0JJ82jCec0vaLzbkx9QSDrnOqTQaZZ66KwqsO/vO2HV0pqBq43zRvOlDQ9C3CixujEkHk4L8KU17+2xHbqCeX67NtnhIYO5/iTsvD8rguSQhOuRb7FPUVujLo4xHBDYG1BugdiH/uxiLkeAgWWfG7CdVMiwD13N5GnuJ1avrySbqf/kKV9GuVFf1gaq9Ol/3OIsvllSbbHH4ZTEGA+wh+308DOLfEsFKv9ZK2rw1nv5OOH5Fus5tvVyFFpLAkwk78pWIv/vLOlBmqYwbsygpB8clhstkJq0EmEEgWZwAYD 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 10/16/25 15:09, Harry Yoo wrote: >> ----8<---- >> From 8151384e5baf34db5812ed51e2e463796ab6e973 Mon Sep 17 00:00:00 2001 >> From: Hao Ge >> Date: Wed, 15 Oct 2025 22:16:42 +0800 >> Subject: [PATCH] slab: reset slab->obj_ext when freeing and it is >> OBJEXTS_ALLOC_FAIL >> >> If obj_exts allocation failed, slab->obj_exts is set to OBJEXTS_ALLOC_FAIL, >> But we do not clear it when freeing the slab. Since OBJEXTS_ALLOC_FAIL and >> MEMCG_DATA_OBJEXTS currently share the same bit position, during the >> release of the associated folio, > >> a VM_BUG_ON_FOLIO() check in >> folio_memcg_kmem() is triggered because it was mistakenly assumed that >> a valid folio->memcg_data was not cleared before freeing the folio. > > nit: maybe this can be massaged as "a VM_BUG_ON_FOLIO() check in folio_memcg_kmem() > is triggered because the OBJEXTS_ALLOC_FAIL flag was not cleared, > causing it to be interpreted as a kmem folio (non-slab) with > MEMCG_OBJEXTS_DATA flag set, which is invalid because MEMCG_OBJEXTS_DATA > is supposed to be set only on slabs." Thanks, applied >> Another problem that predates sharing the OBJEXTS_ALLOC_FAIL and >> MEMCG_DATA_OBJEXTS bits is that on configurations with >> is_check_pages_enabled(), the non-cleared bit in page->memcg_data will >> trigger a free_page_is_bad() failure "page still charged to cgroup" >> >> When freeing a slab, we clear slab->obj_exts if the obj_ext array has >> been successfully allocated. So let's clear it also when the allocation >> has failed. >> >> Fixes: 09c46563ff6d ("codetag: debug: introduce OBJEXTS_ALLOC_FAIL to mark failed slab_ext allocations") >> Link: https://lore.kernel.org/all/20251015141642.700170-1-hao.ge@linux.dev/ >> Cc: >> Signed-off-by: Hao Ge >> Signed-off-by: Vlastimil Babka >> --- > > Looks good to me, > Reviewed-by: Harry Yoo and this too.