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[94.245.46.49]) by smtp.gmail.com with ESMTPSA id d9sm8914864ljg.39.2020.04.05.12.21.14 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 05 Apr 2020 12:21:15 -0700 (PDT) From: Uladzislau Rezki X-Google-Original-From: Uladzislau Rezki Date: Sun, 5 Apr 2020 21:21:08 +0200 To: William Kucharski Cc: William Kucharski , Peter Zijlstra , Andrew Morton , linux-kernel@vger.kernel.org, linux-mm@kvack.org, jroedel@suse.de, vbabka@suse.cz, Thomas Gleixner Subject: Re: [PATCH] mm/vmalloc: Sanitize __get_vm_area() arguments Message-ID: <20200405192108.GA9429@pc636> References: <20200404185229.GA424@pc636> <20200405172315.GA8404@pc636> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20200405172315.GA8404@pc636> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Apr 05, 2020 at 07:23:15PM +0200, Uladzislau Rezki wrote: > On Sat, Apr 04, 2020 at 11:25:45PM -0600, William Kucharski wrote: > > > > > > > On Apr 4, 2020, at 12:52 PM, Uladzislau Rezki wrote: > > > > > >> > > >> Is there any need to similarly sanitize “size” to assure start + size doesn’t go past “end?” > > >> > > > Why is that double check needed if all such tests are done deeper on stack? > > > > If such tests ARE performed, then it doesn't matter to me whether it is checked before or after, > > it just seems that nothing checks whether start + size makes some sort of sense with respect > > to end. > > > > I admit I didn't walk through all the routines to see if such a check would be superfluous. > > > Yes, we check it: > > > static __always_inline bool > is_within_this_va(struct vmap_area *va, unsigned long size, > unsigned long align, unsigned long vstart) > { > ... > return (nva_start_addr + size <= va->va_end); > } > > Sorry, was thinking about one place showed different one. Here we go: /* Check the "vend" restriction. */ if (nva_start_addr + size > vend) return vend; -- Vlad Rezki