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Tue, 14 Oct 2025 08:44:52 +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 lLXQA4QN7mjJIwAAD6G6ig (envelope-from ); Tue, 14 Oct 2025 08:44:52 +0000 Message-ID: <1dbe9c35-9ce7-47b5-ae32-f406bdff58fd@suse.cz> Date: Tue, 14 Oct 2025 10:44:51 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] slab: fix clearing freelist in free_deferred_objects() To: Andrew Morton , Christoph Lameter , David Rientjes , Roman Gushchin , Harry Yoo , Alexei Starovoitov , linux-mm@kvack.org, linux-kernel@vger.kernel.org Cc: kernel test robot References: <20251014-fix-freelist-v1-1-e402301f276d@suse.cz> Content-Language: en-US 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: <20251014-fix-freelist-v1-1-e402301f276d@suse.cz> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Action: no action X-Rspamd-Queue-Id: C2F9D40014 X-Rspamd-Server: rspam11 X-Rspam-User: X-Stat-Signature: 6btjucj6hrunkn7eeu1soc8rtxk9zs4s X-HE-Tag: 1760431493-255258 X-HE-Meta: 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 LWxg1VxK dbZtTiFlqhmsQke59Ns4udvzHTMvp3vzXivDf0qTwMa+bmmxJ1WVhqo6XHcEZloueRuLoB73PFoeaB3l+D4YQb63jibuJH97j1xXSW4dG+949tMve8qMTufblmTemJWP2lqWhrenq/cYZ65ZN+4uYrn5ypU1TEGYxw9a/tjT2rsm0IgOv2e3Qkq+7dPuDzvKtXxw/WXPv2wRJD0RafV0S5jJEGIsaTaW1TOf8vbbo00ySEKBeiyvhmlvZwb9uPehsl1qTHAEwaJZ07pvSx0XrM0rC4F/3hT9sQGQBjDbWE+b93rHqr+Dz7u323B7X+Ze46tGtz7hNrHNDUUHz2wqIdz6AjX+zR9tolYa9T6uHPcIE8UhquRlcxFNlyJRhlOGW1+ci 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 10/14/25 10:40, Vlastimil Babka wrote: > defer_free() links pending objects using the slab's freelist offset > which is fine as they are not free yet. free_deferred_objects() then > clears this pointer to avoid confusing the debugging consistency checks > that may be enabled for the cache. > > However, with CONFIG_SLAB_FREELIST_HARDENED, even the NULL pointer needs > to be encoded appropriately using set_freepointer(), otherwise it's > decoded as something else and triggers the consistency checks, as found > by the kernel test robot. > > Use set_freepointer() to prevent the issue. > > Fixes: af92793e52c3 ("slab: Introduce kmalloc_nolock() and kfree_nolock().") > Reported-by: kernel test robot > Closes: https://lore.kernel.org/oe-lkp/202510101652.7921fdc6-lkp@intel.com > Acked-by: Alexei Starovoitov > Signed-off-by: Vlastimil Babka > --- > will be added to slab/for-next-fixes and sent later this week > --- > mm/slub.c | 7 ++++--- > 1 file changed, 4 insertions(+), 3 deletions(-) > > diff --git a/mm/slub.c b/mm/slub.c > index b1f15598fbfd..64c17afc375b 100644 > --- a/mm/slub.c > +++ b/mm/slub.c > @@ -6443,15 +6443,16 @@ static void free_deferred_objects(struct irq_work *work) > slab = virt_to_slab(x); > s = slab->slab_cache; > > + extra newline moved... > + /* Point 'x' back to the beginning of allocated object */ > + x -= s->offset; ... here. noticed and fixed up locally after sending... > /* > * We used freepointer in 'x' to link 'x' into df->objects. > * Clear it to NULL to avoid false positive detection > * of "Freepointer corruption". > */ > - *(void **)x = NULL; > + set_freepointer(s, x, NULL); > > - /* Point 'x' back to the beginning of allocated object */ > - x -= s->offset; > __slab_free(s, slab, x, x, 1, _THIS_IP_); > } > > > --- > base-commit: 3a8660878839faadb4f1a6dd72c3179c1df56787 > change-id: 20251014-fix-freelist-29915edcc2f4 > > Best regards,