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Thu, 5 Mar 2020 09:16:43 +0100 (CET) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 8F9FE20D3014E; Thu, 5 Mar 2020 09:18:42 +0100 (CET) Date: Thu, 5 Mar 2020 09:18:42 +0100 From: Peter Zijlstra To: Randy Dunlap Cc: akpm@linux-foundation.org, broonie@kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-next@vger.kernel.org, mhocko@suse.cz, mm-commits@vger.kernel.org, sfr@canb.auug.org.au, Josh Poimboeuf , walter-zh.wu@mediatek.com, dvyukov@google.com Subject: Re: mmotm 2020-03-03-22-28 uploaded (warning: objtool:) Message-ID: <20200305081842.GB2619@hirez.programming.kicks-ass.net> References: <20200304062843.9yA6NunM5%akpm@linux-foundation.org> <20200305081717.GT2596@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200305081717.GT2596@hirez.programming.kicks-ass.net> User-Agent: Mutt/1.10.1 (2018-07-13) 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 Thu, Mar 05, 2020 at 09:17:17AM +0100, Peter Zijlstra wrote: > On Wed, Mar 04, 2020 at 09:34:49AM -0800, Randy Dunlap wrote: > > mm/kasan/common.o: warning: objtool: kasan_report()+0x13: call to report_enabled() with UACCESS enabled > > I used next/master instead, and found the below broken commit > responsible for this. > @@ -634,12 +637,20 @@ void kasan_free_shadow(const struct vm_struct *vm) > #endif > > extern void __kasan_report(unsigned long addr, size_t size, bool is_write, unsigned long ip); > +extern bool report_enabled(void); > > -void kasan_report(unsigned long addr, size_t size, bool is_write, unsigned long ip) > +bool kasan_report(unsigned long addr, size_t size, bool is_write, unsigned long ip) > { > - unsigned long flags = user_access_save(); > + unsigned long flags; > + > + if (likely(!report_enabled())) > + return false; This adds an explicit call before the user_access_save() and that is a straight on bug. > + > + flags = user_access_save(); > __kasan_report(addr, size, is_write, ip); > user_access_restore(flags); > + > + return true; > }