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Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1qKIHo-0013fW-LQ; Fri, 14 Jul 2023 12:52:40 +0000 Date: Fri, 14 Jul 2023 13:52:40 +0100 From: Matthew Wilcox To: linke li Cc: David Hildenbrand , Linke Li , linux-mm@kvack.org, llvm@lists.linux.dev, linux-kernel@vger.kernel.org, trix@redhat.com, ndesaulniers@google.com, nathan@kernel.org, muchun.song@linux.dev, mike.kravetz@oracle.com Subject: Re: [PATCH] hugetlbfs: Fix integer overflow check in hugetlbfs_file_mmap() Message-ID: References: <65f4c60a-9534-56dc-099f-ee7a96e0ccaf@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspam-User: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: ECED14000E X-Stat-Signature: pwmcj6k97nbrximdbwdw4nf3dnun3cy3 X-HE-Tag: 1689339175-118134 X-HE-Meta: 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 Gxd52P7b S6lpAKZ/svsTOxom36WO1f+W6aV3i+O4fzOUWPMByyWl9pEBBFAoWKl9FKx+Xah2mL85jxIEmVmIKnbi/A88TM7h2E8X0dFHKNXFSDyPICWY/agnvtYQfJGGMdYAZuzYSeWjhtjXdgBMNNvDfwZKDq6a0WTQit1+gZzHzmI6zaD43y74L2OgElnCHnA== 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, Jul 13, 2023 at 03:55:55PM +0800, linke li wrote: > > So we're adding code to handle eventual future compiler bugs? That sounds > > wrong, but maybe I misunderstood the problem you are trying to solve? > > Sorry for not making it clear. My focus is the presence of undefined > behavior in kernel code. > Compilers can generate any code for undefined behavior and compiler > developers will not > take this as compiler bugs. In my option, kernel should not have > undefined behavior. The point that several people have tried to make to you is that *this is not undefined behaviour*. The kernel is compiled with -fno-strict-overflow which causes the compiler to define signed arithmetic overflow to behave as twos-complement. Check the gcc documentation.