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Tue, 11 Nov 2025 13:13:22 +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 sxTwH3I2E2mkUQAAD6G6ig (envelope-from ); Tue, 11 Nov 2025 13:13:22 +0000 Message-ID: Date: Tue, 11 Nov 2025 14:13:22 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH V1] mm/slub: fix memory leak in free_to_pcs_bulk() Content-Language: en-US To: Harry Yoo , Andrew Morton Cc: "Liam R . Howlett" , Tytus Rogalewski , "Darrick J . Wong" , Christoph Lameter , David Rientjes , Roman Gushchin , linux-mm@kvack.org References: <20251111125331.12246-1-harry.yoo@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: <20251111125331.12246-1-harry.yoo@oracle.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam12 X-Rspam-User: X-Rspamd-Queue-Id: 8A74E180004 X-Stat-Signature: ibd6i78wjpg9ji83faqnzmniepbraswq X-HE-Tag: 1762866804-945762 X-HE-Meta: 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 fdMSKG8E MwzvOUjUQD6vLs2dvjoHl9GCaTK/dyCEdkmSi5RZWQtZYZEi+qMU9FYDlye6Vlh5/qXhhsjka2LCMWlxxTRdjwLxUgMvPepqDlOC/EW0BEi8kpprruZ3LgbVhqaLrJJVRAEyEKUoNAeRx2kvnIOG2mwcofJlH/EeiYdsXwmV2Sn5iAZf6BwTk0jrOjHx0pXBgD+1PjjlkdW8ExuxuO+5TGDjRqaIMWAXoUt9pfbTZvG+VyjVsKRfKPMyL8aK3ocIvZkujcnWxPddsxQkBo7R+Wn672uUrl1sFQ0itzNIHLXAcwa67vxOwE/qDeP6A91l4JW/1t+gE82C4KP4NFRcrjQZPrWIFi+TQJCLIEXgmr9DJnupC3weMxy/cZWNN1yZInOS3Sp+wTvhG4qRbk+bOBh4seKdlCm8bn0QFUScs8yiu/FYOSiFsZqZ4Emo4yvzDR3dc8OxWiHN14EM= 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 11/11/25 13:53, Harry Yoo wrote: > The commit 989b09b73978 ("slab: skip percpu sheaves for remote object > freeing") introduced the remote_objects array in free_to_pcs_bulk() to > skip sheaves when objects from a remote node are freed. > > However, the array is flushed only when: > 1) the array becomes full (++remote_nr >= PCS_BATCH_MAX), or > 2) slab_free_hook() returns false and size becomes zero. > > When neither of the conditions is met, objects in the array are leaked. > This resulted in a memory leak [1], where 82 GiB of memory was allocated > for the maple_node cache. > > Flush the array after successfully freeing objects to sheaves > in the do_free: path. > > In the meantime, move the snippet if (!size) goto flush_remote; outside > the while loop for readability. Let's say all objects in the array are > from a remote node: then we acquire s->cpu_sheaves->lock and try to free > an object even when size is zero. This doesn't appear to be harmful, > but isn't really readable. > > Reported-by: Tytus Rogalewski > Closes: https://bugzilla.kernel.org/show_bug.cgi?id=220765 [1] > Closes: https://lore.kernel.org/linux-mm/20251107094809.12e9d705b7bf4815783eb184@linux-foundation.org > Closes: https://lore.kernel.org/all/aRGDTwbt2EIz2CYn@hyeyoo > Fixes: 989b09b73978 ("slab: skip percpu sheaves for remote object freeing") > Signed-off-by: Harry Yoo Thanks a lot! Adding to slab/for-next-fixes Vlastimil > --- > mm/slub.c | 8 ++++++-- > 1 file changed, 6 insertions(+), 2 deletions(-) > > diff --git a/mm/slub.c b/mm/slub.c > index f1a5373eee7b..a787687a0d59 100644 > --- a/mm/slub.c > +++ b/mm/slub.c > @@ -6332,8 +6332,6 @@ static void free_to_pcs_bulk(struct kmem_cache *s, size_t size, void **p) > > if (unlikely(!slab_free_hook(s, p[i], init, false))) { > p[i] = p[--size]; > - if (!size) > - goto flush_remote; > continue; > } > > @@ -6348,6 +6346,9 @@ static void free_to_pcs_bulk(struct kmem_cache *s, size_t size, void **p) > i++; > } > > + if (!size) > + goto flush_remote; > + > next_batch: > if (!local_trylock(&s->cpu_sheaves->lock)) > goto fallback; > @@ -6402,6 +6403,9 @@ static void free_to_pcs_bulk(struct kmem_cache *s, size_t size, void **p) > goto next_batch; > } > > + if (remote_nr) > + goto flush_remote; > + > return; > > no_empty: