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Fri, 12 Sep 2025 11:34:08 +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 ReskIzAFxGhEagAAD6G6ig (envelope-from ); Fri, 12 Sep 2025 11:34:08 +0000 Message-ID: <96ee75c2-d561-4e9b-977f-72a3b056a08f@suse.cz> Date: Fri, 12 Sep 2025 13:34:08 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 5/6] slab: validate slab before using it in alloc_single_from_partial() Content-Language: en-US To: Harry Yoo Cc: "Matthew Wilcox (Oracle)" , Christoph Lameter , David Rientjes , Roman Gushchin , Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20250911-slub-slab-validation-v1-0-8b67eb3b3dc5@suse.cz> <20250911-slub-slab-validation-v1-5-8b67eb3b3dc5@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-Spamd-Result: default: False [-4.30 / 50.00]; BAYES_HAM(-3.00)[100.00%]; NEURAL_HAM_LONG(-1.00)[-1.000]; NEURAL_HAM_SHORT(-0.20)[-0.998]; MIME_GOOD(-0.10)[text/plain]; FUZZY_RATELIMITED(0.00)[rspamd.com]; RCVD_VIA_SMTP_AUTH(0.00)[]; ARC_NA(0.00)[]; RCPT_COUNT_SEVEN(0.00)[8]; MID_RHS_MATCH_FROM(0.00)[]; RCVD_TLS_ALL(0.00)[]; DKIM_SIGNED(0.00)[suse.cz:s=susede2_rsa,suse.cz:s=susede2_ed25519]; FROM_HAS_DN(0.00)[]; MIME_TRACE(0.00)[0:+]; FROM_EQ_ENVFROM(0.00)[]; TO_MATCH_ENVRCPT_ALL(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; TO_DN_SOME(0.00)[] X-Spam-Flag: NO X-Spam-Level: X-Spam-Score: -4.30 On 9/12/25 12:48, Harry Yoo wrote: > On Thu, Sep 11, 2025 at 07:02:38PM +0200, Vlastimil Babka wrote: >> We touch slab->freelist and slab->inuse before checking the slab pointer >> is actually sane. Do that validation first, which will be safer. We can >> thus also remove the check from alloc_debug_processing(). >> >> This adds a new "s->flags & SLAB_CONSISTENCY_CHECKS" test but >> alloc_single_from_partial() is only called for caches with debugging >> enabled so it's acceptable. >> >> In alloc_single_from_new_slab() we just created the struct slab and call >> alloc_debug_processing() to mainly set up redzones, tracking etc, while >> not really expecting the consistency checks to fail. Thus don't validate >> it there. >> >> Signed-off-by: Vlastimil Babka >> --- >> mm/slub.c | 17 ++++++++--------- >> 1 file changed, 8 insertions(+), 9 deletions(-) >> >> diff --git a/mm/slub.c b/mm/slub.c >> index 909c71372a2f542b6e0d67c12ea683133b246b66..93df6e82af37c798c3fa5574c9d825f0f4a83013 100644 >> --- a/mm/slub.c >> +++ b/mm/slub.c >> @@ -1651,11 +1651,6 @@ static noinline bool alloc_debug_processing(struct kmem_cache *s, >> struct slab *slab, void *object, int orig_size) >> { >> if (s->flags & SLAB_CONSISTENCY_CHECKS) { >> - if (!validate_slab_ptr(slab)) { >> - slab_err(s, slab, "Not a valid slab page"); >> - return false; >> - } >> - >> if (!alloc_consistency_checks(s, slab, object)) >> goto bad; >> } >> @@ -2825,15 +2820,19 @@ static void *alloc_single_from_partial(struct kmem_cache *s, >> >> lockdep_assert_held(&n->list_lock); >> >> + if (s->flags & SLAB_CONSISTENCY_CHECKS) { >> + if (!validate_slab_ptr(slab)) { >> + slab_err(s, slab, "Not a valid slab page"); >> + return NULL; >> + } >> + } >> + >> object = slab->freelist; >> slab->freelist = get_freepointer(s, object); >> slab->inuse++; >> >> - if (!alloc_debug_processing(s, slab, object, orig_size)) { >> - if (validate_slab_ptr(slab)) >> - remove_partial(n, slab); >> + if (!alloc_debug_processing(s, slab, object, orig_size)) >> return NULL; > > Is it intentional to not remove the slab from the partial list > when alloc_debug_processing() returns false? No, good catch, will fix. Thanks! >> - } >> >> if (slab->inuse == slab->objects) { >> remove_partial(n, slab); >> >> -- >> 2.51.0 >