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[195.135.220.15]) by mx.google.com with ESMTPS id l56si9182733edd.41.2019.06.17.07.50.19 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 17 Jun 2019 07:50:19 -0700 (PDT) Received-SPF: pass (google.com: domain of rpenyaev@suse.de designates 195.135.220.15 as permitted sender) client-ip=195.135.220.15; Authentication-Results: mx.google.com; spf=pass (google.com: domain of rpenyaev@suse.de designates 195.135.220.15 as permitted sender) smtp.mailfrom=rpenyaev@suse.de X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 6B7B3AEF1; Mon, 17 Jun 2019 14:50:18 +0000 (UTC) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII; format=flowed Content-Transfer-Encoding: 7bit Date: Mon, 17 Jun 2019 16:50:17 +0200 From: Roman Penyaev To: Arnd Bergmann Cc: Uladzislau Rezki , Roman Gushchin , Michal Hocko , Matthew Wilcox , Thomas Garnier , Oleksiy Avramchenko , Steven Rostedt , Joel Fernandes , Thomas Gleixner , Ingo Molnar , Tejun Heo , Andrew Morton , Linus Torvalds , Stephen Rothwell , Rick Edgecombe , Andrey Ryabinin , Mike Rapoport , Linux-MM , Linux Kernel Mailing List Subject: Re: [BUG]: mm/vmalloc: uninitialized variable access in pcpu_get_vm_areas In-Reply-To: References: <20190617121427.77565-1-arnd@arndb.de> <20190617141244.5x22nrylw7hodafp@pc636> Message-ID: X-Sender: rpenyaev@suse.de User-Agent: Roundcube Webmail 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: On 2019-06-17 16:44, Arnd Bergmann wrote: > On Mon, Jun 17, 2019 at 4:12 PM Uladzislau Rezki > wrote: >> >> On Mon, Jun 17, 2019 at 02:14:11PM +0200, Arnd Bergmann wrote: >> > gcc points out some obviously broken code in linux-next >> > >> > mm/vmalloc.c: In function 'pcpu_get_vm_areas': >> > mm/vmalloc.c:991:4: error: 'lva' may be used uninitialized in this function [-Werror=maybe-uninitialized] >> > insert_vmap_area_augment(lva, &va->rb_node, >> > ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ >> > &free_vmap_area_root, &free_vmap_area_list); >> > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ >> > mm/vmalloc.c:916:20: note: 'lva' was declared here >> > struct vmap_area *lva; >> > ^~~ >> > >> > Remove the obviously broken code. This is almost certainly >> > not the correct solution, but it's what I have applied locally >> > to get a clean build again. >> > >> > Please fix this properly. >> > > >> > >> Please do not apply this. It will just break everything. > > As I wrote in my description, this was purely meant as a bug > report, not a patch to be applied. That's a perfect way to attract attention! :) > >> As Roman pointed we can just set lva = NULL; in the beginning to make >> GCC happy. >> For some reason GCC decides that it can be used uninitialized, but >> that >> is not true. > > I got confused by the similarly named FL_FIT_TYPE/NE_FIT_TYPE Names are indeed very confusing, that is true. Very easy to mix up things. -- Roman