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Content-Language: en-US To: Alexei Starovoitov Cc: Kuniyuki Iwashima , Andrew Morton , Christoph Lameter , David Rientjes , Roman Gushchin , Harry Yoo , Alexei Starovoitov , Kuniyuki Iwashima , linux-mm , syzbot+a6f4d69b9b23404bbabf@syzkaller.appspotmail.com References: <20251007052534.2776661-1-kuniyu@google.com> <10d6dec4-665d-493f-97a9-2982dfbc1afe@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: 8bit X-Rspamd-Server: rspam01 X-Stat-Signature: zuysz16jrpz1krai84jnp19uaxojsa4n X-Rspam-User: X-Rspamd-Queue-Id: E48DF1C0006 X-HE-Tag: 1759860476-616789 X-HE-Meta: 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 RwhjApJs OTurg5TarisC0HKCHJEFiUaiVZn0W8twVn9LDGvJlSZ3X7ovEvn2SbfOt1Ce83H1m9AAycCmqpcWNljTjSZljxVH6dWSUbzqOL4dxIGLP0Ns7jacVI6KrNX5XA6HmWgVxHCQ74y9drhqc0Lga7iK5z3MzS/HbY9eWPSfloS6uNmBASUnj1O6JHlg/N+CZH1FlUaAyoNOgjxbsK3f3UyuLgSqrpwFP7L5ueclG3RJof+v1mdzbRByCed60Yup6Cr4w9MStd/7sXrUtvmHItTrj6Nqkz069i0gbyNHgD/k2ej21334P2psKrZLCSgDfQYfArYlhefhSSYYRKnl1NQHyfICEMj8w2XYXBqK6mV/jQ6OQTXwwOxxXIMG3L4bNapftDilADBIwpPpKSw959goqh2zYwZ1xwav1E+ri9IiTrscYA4+8sYh4kMqxcrrIGoFC9Y48w10jIba7QGw= 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 10/7/25 18:11, Alexei Starovoitov wrote: > On Tue, Oct 7, 2025 at 12:46 AM Vlastimil Babka wrote: >> >> On 10/7/25 07:25, Kuniyuki Iwashima wrote: >> > syzbot reported the lockdep splat below in __kmem_cache_release(). [0] >> > >> > The problem is that __kmem_cache_release() could be called from >> > do_kmem_cache_create() before init_kmem_cache_cpus() registers >> > the lockdep key. > > Hmm. If that's the case then alloc_kmem_cache_cpus() wasn't called yet > and s->cpu_slab == NULL, so any kmalloc/kmem_cache_alloc from > that slub will crash. The above sounds like it's a race condition, > but it's not. It's a weird error path in do_kmem_cache_create() Indeed. > due to syzbot pressure. > So the fix isn't quite right. > There is no need to sprinkle #ifdef all over the code. > >> > >> > Let's move lockdep_unregister_key() from __kmem_cache_release() >> > to slab_kmem_cache_release() and do_kmem_cache_create(). > > I wouldn't. > >> Thanks, added to slab/for-next-fixes > > The following is imo much cleaner fix: Yes much better, I'm changing it. Thanks! > diff --git a/mm/slub.c b/mm/slub.c > index 584a5ff1828b..0a1fbddb77f8 100644 > --- a/mm/slub.c > +++ b/mm/slub.c > @@ -7693,7 +7693,8 @@ void __kmem_cache_release(struct kmem_cache *s) > pcs_destroy(s); > #ifndef CONFIG_SLUB_TINY > #ifdef CONFIG_PREEMPT_RT > - lockdep_unregister_key(&s->lock_key); > + if (s->cpu_slab) > + lockdep_unregister_key(&s->lock_key); > #endif > free_percpu(s->cpu_slab); > #endif > > compile tested only...