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Tue, 10 Sep 2024 13:15:36 +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 hlbcNXhG4GasGQAAD6G6ig (envelope-from ); Tue, 10 Sep 2024 13:15:36 +0000 Message-ID: Date: Tue, 10 Sep 2024 15:15:36 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 3/5] mm/slub: Improve redzone check and zeroing for krealloc() Content-Language: en-US To: Feng Tang , Andrew Morton , Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Roman Gushchin , Hyeonggon Yoo <42.hyeyoo@gmail.com>, Andrey Konovalov , Marco Elver , Shuah Khan , David Gow , Danilo Krummrich Cc: linux-mm@kvack.org, kasan-dev@googlegroups.com, linux-kernel@vger.kernel.org References: <20240909012958.913438-1-feng.tang@intel.com> <20240909012958.913438-4-feng.tang@intel.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+fMgqZkBQJkBREIBQkRadznAAoJECJPp+fMgqZkNxIQ ALZRqwdUGzqL2aeSavbum/VF/+td+nZfuH0xeWiO2w8mG0+nPd5j9ujYeHcUP1edE7uQrjOC Gs9sm8+W1xYnbClMJTsXiAV88D2btFUdU1mCXURAL9wWZ8Jsmz5ZH2V6AUszvNezsS/VIT87 AmTtj31TLDGwdxaZTSYLwAOOOtyqafOEq+gJB30RxTRE3h3G1zpO7OM9K6ysLdAlwAGYWgJJ V4JqGsQ/lyEtxxFpUCjb5Pztp7cQxhlkil0oBYHkudiG8j1U3DG8iC6rnB4yJaLphKx57NuQ PIY0Bccg+r9gIQ4XeSK2PQhdXdy3UWBr913ZQ9AI2usid3s5vabo4iBvpJNFLgUmxFnr73SJ KsRh/2OBsg1XXF/wRQGBO9vRuJUAbnaIVcmGOUogdBVS9Sun/Sy4GNA++KtFZK95U7J417/J Hub2xV6Ehc7UGW6fIvIQmzJ3zaTEfuriU1P8ayfddrAgZb25JnOW7L1zdYL8rXiezOyYZ8Fm ZyXjzWdO0RpxcUEp6GsJr11Bc4F3aae9OZtwtLL/jxc7y6pUugB00PodgnQ6CMcfR/HjXlae h2VS3zl9+tQWHu6s1R58t5BuMS2FNA58wU/IazImc/ZQA+slDBfhRDGYlExjg19UXWe/gMcl De3P1kxYPgZdGE2eZpRLIbt+rYnqQKy8UxlszsBNBFsZNTUBCACfQfpSsWJZyi+SHoRdVyX5 J6rI7okc4+b571a7RXD5UhS9dlVRVVAtrU9ANSLqPTQKGVxHrqD39XSw8hxK61pw8p90pg4G /N3iuWEvyt+t0SxDDkClnGsDyRhlUyEWYFEoBrrCizbmahOUwqkJbNMfzj5Y7n7OIJOxNRkB IBOjPdF26dMP69BwePQao1M8Acrrex9sAHYjQGyVmReRjVEtv9iG4DoTsnIR3amKVk6si4Ea X/mrapJqSCcBUVYUFH8M7bsm4CSxier5ofy8jTEa/CfvkqpKThTMCQPNZKY7hke5qEq1CBk2 wxhX48ZrJEFf1v3NuV3OimgsF2odzieNABEBAAHCwXwEGAEKACYCGwwWIQSpQNQ0mSwujpkQ PVAiT6fnzIKmZAUCZAUSmwUJDK5EZgAKCRAiT6fnzIKmZOJGEACOKABgo9wJXsbWhGWYO7mD 8R8mUyJHqbvaz+yTLnvRwfe/VwafFfDMx5GYVYzMY9TWpA8psFTKTUIIQmx2scYsRBUwm5VI EurRWKqENcDRjyo+ol59j0FViYysjQQeobXBDDE31t5SBg++veI6tXfpco/UiKEsDswL1WAr tEAZaruo7254TyH+gydURl2wJuzo/aZ7Y7PpqaODbYv727Dvm5eX64HCyyAH0s6sOCyGF5/p eIhrOn24oBf67KtdAN3H9JoFNUVTYJc1VJU3R1JtVdgwEdr+NEciEfYl0O19VpLE/PZxP4wX PWnhf5WjdoNI1Xec+RcJ5p/pSel0jnvBX8L2cmniYnmI883NhtGZsEWj++wyKiS4NranDFlA HdDM3b4lUth1pTtABKQ1YuTvehj7EfoWD3bv9kuGZGPrAeFNiHPdOT7DaXKeHpW9homgtBxj 8aX/UkSvEGJKUEbFL9cVa5tzyialGkSiZJNkWgeHe+jEcfRT6pJZOJidSCdzvJpbdJmm+eED w9XOLH1IIWh7RURU7G1iOfEfmImFeC3cbbS73LQEFGe1urxvIH5K/7vX+FkNcr9ujwWuPE9b 1C2o4i/yZPLXIVy387EjA6GZMqvQUFuSTs/GeBcv0NjIQi8867H3uLjz+mQy63fAitsDwLmR EP+ylKVEKb0Q2A== In-Reply-To: <20240909012958.913438-4-feng.tang@intel.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 8D0A11A0016 X-Stat-Signature: uzh4tnhbptp6hket9au6rb4p8cf93dg3 X-Rspam-User: X-HE-Tag: 1725974138-177153 X-HE-Meta: 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 oYJiUmNl uVYOwNxPKRsLzbbkzWUoibwbgs53e4NBQiKNmN8VPZiVAbmHP6QxMmNzwhrMkAQCJy6QREOslchJW1rf+2FN9bZxWvLD9wBqyMXofWXnffcS9IHYtqF/KuZPCsEJXEOQydIH75U9FLhJtSBwj6X1YJjLP807looC5ias5ePKtFMmnHnya8EBGx+GIZUs5oUJhZ9JNOPFL1ZANniMPPMyOfZyfLld6l5PgSM9JGbuZmKjxwk+pU41I9RbsDQovLf3NHU8P6AjIaFasqyRveb7CJ4zPg6sdDIcBbCSLVjdktYNicttu7tLJM6K7o1qsSc6LUsa3yHt7jtlEHf5F/pzIP9e+/1PUNPV6BkENx+PXkBXU7L8= 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 9/9/24 03:29, Feng Tang wrote: > For current krealloc(), one problem is its caller doesn't know what's > the actual request size, say the object is 64 bytes kmalloc one, but It's more accurate to say the caller doesn't pass the old size (it might actually know it). > the original caller may only requested 48 bytes. And when krealloc() > shrinks or grows in the same object, or allocate a new bigger object, > it lacks this 'original size' information to do accurate data preserving > or zeroing (when __GFP_ZERO is set). Let's describe the problem specifically by adding: Thus with slub debug redzone and object tracking enabled, parts of the object after krealloc() might contain redzone data instead of zeroes, which is violating the __GFP_ZERO guarantees. > And when some slub debug option is enabled, kmalloc caches do have this > 'orig_size' feature. So utilize it to do more accurate data handling, > as well as enforce the kmalloc-redzone sanity check. > > The krealloc() related code is moved from slab_common.c to slub.c for > more efficient function calling. Agreed with Danilo that having the move as separate preparatory patch would make review easier. Thanks.