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b=tIon9ft3SeC38O+vPFHnF01jrKNgQPFlxEa5IXpsLMzcS1U9c4DG+2aGopwjNesUF ceLyJnbxrdexJTOgff+9LRAYGJxALPHm4UA8T6ZTbsqVY4Q6DT2qr0O/IV3BlB2CH9 4cAVeAcmpgo9YTouEqSk3CpmAlQ2msxf9wqMiwI7KHZGAdivR6v/LmJ6GfUBJsju+E KcjFip7moMdV7IeN3de6X2zLElLSDBVJn/e+XD7UsnvOC0uZFGBu2aVCTywL9y8oH1 Mvzm9w/cz7pTFoGOY91H+4me/sba/qVar8c4FdQQDoX90Nt46zAYXvtQdk+rOxbEsi PDp78bQWtJwcg== Date: Wed, 3 Jul 2024 16:08:56 +0200 From: Christian Brauner To: Mateusz Guzik Cc: Linus Torvalds , kernel test robot , oe-lkp@lists.linux.dev, lkp@intel.com, Linux Memory Management List , linux-kernel@vger.kernel.org, ying.huang@intel.com, feng.tang@intel.com, fengwei.yin@intel.com Subject: Re: [linux-next:master] [lockref] d042dae6ad: unixbench.throughput -33.7% regression Message-ID: <20240703-haftstrafe-anbringen-88ed445e77a4@brauner> References: <3g3arsrwnyvv562v2rsfv2ms4ht4mk45vwdkvssxkrjhfjtpdz@umyx5tl2du7o> <6knlkefvujkry65gx6636u6e7rivqrn5kqjovs4ctjg7xtzrmo@2zd4wjx6zcym> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 7BE0A4000B X-Stat-Signature: a39oydza8oqpu6514hw1g6poqxzhjsg9 X-HE-Tag: 1720015744-220172 X-HE-Meta: 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 UGGeJu/B TA16ij6CNPqHwhnWf9jylUyka7cstFHKKXJq23jue127YuRp4KYE6WcVvRkII7qJ4YpholBcTYnXFJJAAZONZrzjs5hUTB50QqKYaGP/OTxim06ITE+AE3dKH81RlV2kqziaCFKEdHdkRIq3jUpHZBSITr3OJdzBz05a/3kntKfyQ8veSH6ukm9D72s3+UwW0g2DzsnxmO12+h1Qz/WtBBdrPE1UT9qdoy37umzTuVulnuOb8z0cHbzdxVMFNb/0bs0E3dD1Hl6brxS4m6m2YAG16HZdrngiEi3FyTXyjyav19Ug= 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: > As a side note this is where I should also note the *current* LSM hooks > are racy as is. Suppose you can stat a particular file now, but a chown > to 1234 means you can't. Then your stat call can race against chown + > other ops. You can end up in a state where LSMs gave a green light and > only then the state changed to one you are not allowed to look at. This Fwiw, we've discussed this before. And my opinion is that we should absolute not care about this. I have no interest in complicating path lookup or any codepath to make these hooks less racy. This raciness they have to deal with. This is not a comment on your patch but just that the raciness of security hooks is not a problem we should care to solve imho. If we go down that road we'll all slowly go insane trying to give state change guarantees to layers that hook into the VFS in really odd locations.