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Received: from 77-249-17-252.cable.dynamic.v4.ziggo.nl ([77.249.17.252] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.98.2 #2 (Red Hat Linux)) id 1u7sKp-0000000BTo6-43mP; Thu, 24 Apr 2025 08:53:32 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id 6A8EA3003FF; Thu, 24 Apr 2025 10:53:31 +0200 (CEST) Date: Thu, 24 Apr 2025 10:53:31 +0200 From: Peter Zijlstra To: Andrew Morton Cc: Mike Rapoport , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] execmem: enforce allocation size aligment to PAGE_SIZE Message-ID: <20250424085331.GD19534@noisy.programming.kicks-ass.net> References: <20250423144808.1619863-1-rppt@kernel.org> <20250423143650.6595dcc7178351b62c31782c@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250423143650.6595dcc7178351b62c31782c@linux-foundation.org> X-Stat-Signature: a8hugmj1tod8qc4ch85chzxyt8s38gk9 X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: CFD5514000E X-Rspam-User: X-HE-Tag: 1745484814-985915 X-HE-Meta: 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 9kntFAky eCxtZuO8AwMAgDwQvy2tQ0pWdJCvo5unmYrwn9ND55gevetyXkoqf9g0kJzsweHRYjXlTEFaZALJiv72Dgky1NOpBPq7E8PT/x1/PWotJQXUqtHtsaKIjNTnXO+TEsC3wi93hdD6RlxIlNv8VaI+IZ1n4l70kCRe1BEY6K9vqbK1xvyaBRY/iFIU/Ysi8r55+RpwsVDtQR7/gU2dnuosgGZgtWAol/7ZP5dFrw2o8crbN7SKRpUStQ5f6YoiLiR0QysVj 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 Wed, Apr 23, 2025 at 02:36:50PM -0700, Andrew Morton wrote: > On Wed, 23 Apr 2025 17:48:07 +0300 Mike Rapoport wrote: > > > Before introduction of ROX cache execmem allocation size was always > > implicitly aligned to PAGE_SIZE inside vmalloc. > > > > However, when allocation happens from the ROX cache, this is not > > enforced. > > > > Make sure that the allocation size is always consistently aligned to > > PAGE_SIZE. > > Does this have any known runtime effect? It should not -- currently all this code is used with PAGE_SIZE multiples and everything just works. But whilst I was perusing this code, I noticed that nothing actually enforced this. If someone were to break this assumption things will go sideways.