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Fri, 9 Jan 2026 17:32:06 +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 n33YOZY7YWm4YQAAD6G6ig (envelope-from ); Fri, 09 Jan 2026 17:32:06 +0000 Message-ID: Date: Fri, 9 Jan 2026 18:32:06 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v6 1/5] slab: Introduce kmalloc_obj() and family Content-Language: en-US To: Kees Cook Cc: Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Andrew Morton , Roman Gushchin , Hyeonggon Yoo <42.hyeyoo@gmail.com>, "Gustavo A . R . Silva" , Bill Wendling , Justin Stitt , Jann Horn , Przemek Kitszel , Marco Elver , Linus Torvalds , Greg Kroah-Hartman , Sasha Levin , linux-mm@kvack.org, Randy Dunlap , Miguel Ojeda , Matthew Wilcox , John Hubbard , Joe Perches , Vegard Nossum , Harry Yoo , Nathan Chancellor , Peter Zijlstra , Nick Desaulniers , Jonathan Corbet , Jakub Kicinski , Yafang Shao , Tony Ambardar , Alexander Lobakin , Jan Hendrik Farr , Alexander Potapenko , linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org, linux-doc@vger.kernel.org, llvm@lists.linux.dev References: <20251203233029.it.641-kees@kernel.org> <20251203233036.3212363-1-kees@kernel.org> <960729bb-0746-4709-a40c-2e254f963deb@suse.cz> <202601090928.5CFF95F@keescook> 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: <202601090928.5CFF95F@keescook> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: DA43618000E X-Stat-Signature: 4wtxehhza7efy9ndjwee6qyhabhjoqwx X-HE-Tag: 1767979928-713482 X-HE-Meta: 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 YBKs7ywS K68foK/6gt+cZq7hvnJz/EbDRbLWIQdaXl/GW7rH5K4WtkVqkUfqA6B3GqEKWGKDQOUu2Qw/kom/T5F18y86LWLzAo0NBeP6cGjuglUTcKX/qux+lfUHksRFpC/6miB4Vprr/cQlE5e61MOpS5EE7Kj0wCp/1Bau/FuhyRUXgR96TmxQrnZpGaqF3ajETYQ9PGUs+Sg5pBBjziHzzFU3hpAMdd8Ic85NpUN8QVcGTE8M1CWu0Ai9n0aLKsGxIBwPb+3VLcg/nXwniBS2OPz8b149luLG2WHZfA6XuH8n5ul2GfluJt4OAY8zLiXWOjMgu4tn8DMNWfkhRc7c/XIUVj7kLGU6/UuA3hb12omyU+Nd7Xt8qkqTkGF2biIf+Nt9nKPDZvqQxBP6uVWVtZZa92X829JqtaPBH60ra 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 1/9/26 18:31, Kees Cook wrote: > On Thu, Jan 08, 2026 at 03:01:00PM +0100, Vlastimil Babka wrote: >> On 12/4/25 00:30, Kees Cook wrote: >> > [...] >> > +/** >> > + * __alloc_objs - Allocate objects of a given type using >> > + * @KMALLOC: which size-based kmalloc wrapper to allocate with. >> > + * @GFP: GFP flags for the allocation. >> > + * @TYPE: type to allocate space for. >> > + * @COUNT: how many @TYPE objects to allocate. >> > + * >> > + * Returns: Newly allocated pointer to (first) @TYPE of @COUNT-many >> > + * allocated @TYPE objects, or NULL on failure. >> > + */ >> > +#define __alloc_objs(KMALLOC, GFP, TYPE, COUNT) \ >> > +({ \ >> > + const size_t __obj_size = size_mul(sizeof(TYPE), COUNT); \ >> >> I assume with the hardcoded 1 for COUNT, this size_mul() will be eliminated >> by the compiler and not add unnecessary runtime overhead? Otherwise we >> should have two core #define variants. > > You're correct: the compiler completely collapses it with 0 runtime > overhead; a variant is not needed. > >> I also noted that the existing kmalloc_array() and kvmalloc_array() do >> check_mul_overflow() and return NULL silently on overflow. This AFAIU will >> make SIZE_MAX passed to the underlying kmalloc/kvmalloc and thus will cause >> a warning. That's IMHO a good thing. > > Right -- I prefer seeing the SIZE_MAX yelling from the allocator. Should > we change how k*malloc_array() behaves? Yeah it should best behave the same I think. > -Kees >