From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f45.google.com (mail-pa0-f45.google.com [209.85.220.45]) by kanga.kvack.org (Postfix) with ESMTP id 025506B0032 for ; Mon, 23 Feb 2015 07:02:05 -0500 (EST) Received: by pabkq14 with SMTP id kq14so27065848pab.3 for ; Mon, 23 Feb 2015 04:02:04 -0800 (PST) Received: from ozlabs.org (ozlabs.org. [103.22.144.67]) by mx.google.com with ESMTPS id c1si1740386pdk.5.2015.02.23.04.02.03 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 23 Feb 2015 04:02:04 -0800 (PST) From: Rusty Russell Subject: Re: [PATCH] kasan, module, vmalloc: rework shadow allocation for modules In-Reply-To: <54E6E684.4070806@samsung.com> References: <1424281467-2593-1-git-send-email-a.ryabinin@samsung.com> <87pp96stmz.fsf@rustcorp.com.au> <54E5E355.9020404@samsung.com> <87fva1sajo.fsf@rustcorp.com.au> <54E6E684.4070806@samsung.com> Date: Mon, 23 Feb 2015 18:56:12 +1030 Message-ID: <87vbithw4b.fsf@rustcorp.com.au> MIME-Version: 1.0 Content-Type: text/plain Sender: owner-linux-mm@kvack.org List-ID: To: Andrey Ryabinin , Andrew Morton Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Dmitry Vyukov Andrey Ryabinin writes: > On 02/20/2015 03:15 AM, Rusty Russell wrote: >> Andrey Ryabinin writes: >>> On 02/19/2015 02:10 AM, Rusty Russell wrote: >>>> This is not portable. Other archs don't use vmalloc, or don't use >>>> (or define) MODULES_VADDR. If you really want to hook here, you'd >>>> need a new flag (or maybe use PAGE_KERNEL_EXEC after an audit). >>>> >>> >>> Well, instead of explicit (addr >= MODULES_VADDR && addr < MODULES_END) >>> I could hide this into arch-specific function: 'kasan_need_to_allocate_shadow(const void *addr)' >>> or make make all those functions weak and allow arch code to redefine them. >> >> That adds another layer of indirection. And how would the caller of >> plain vmalloc() even know what to return? >> > > I think I don't understand what do you mean here. vmalloc() callers shouldn't know > anything about kasan/shadow. How else would kasan_need_to_allocate_shadow(const void *addr) work for architectures which don't have a reserved vmalloc region for modules? >> Hmm, how about a hybrid: >> >> 1) Add kasan_module_alloc(p, size) after module alloc as your original. >> 2) Hook into vfree(), and ignore it if you can't find the map. >> > > That should work, but it looks messy IMO. > >> Or is the latter too expensive? >> > > Not sure whether this will be too expensive or not, > but definitely more expensive than simple (addr >= MODULES_VADDR && addr < MODULES_END) check. Sure, if that check were portable. If you ever wanted kasan on other vmalloc addresses it wouldn't work either. I actually think this pattern is the *simplest* solution for auxilliary data like kasan. Cheers, Rusty. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org