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[156.34.48.30]) by smtp.gmail.com with ESMTPSA id 196sm1857233qkm.49.2020.09.30.05.30.01 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 30 Sep 2020 05:30:01 -0700 (PDT) Received: from jgg by mlx with local (Exim 4.94) (envelope-from ) id 1kNbFA-003w5a-MC; Wed, 30 Sep 2020 09:30:00 -0300 Date: Wed, 30 Sep 2020 09:30:00 -0300 From: Jason Gunthorpe To: Jann Horn Cc: Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org, "Eric W . Biederman" , Michel Lespinasse , Mauro Carvalho Chehab , Sakari Ailus Subject: Re: [PATCH 3/4] mmap locking API: Don't check locking if the mm isn't live yet Message-ID: <20200930123000.GC9916@ziepe.ca> References: <20200930011944.19869-1-jannh@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: 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 Tue, Sep 29, 2020 at 06:20:00PM -0700, Jann Horn wrote: > In preparation for adding a mmap_assert_locked() check in > __get_user_pages(), teach the mmap_assert_*locked() helpers that it's fine > to operate on an mm without locking in the middle of execve() as long as > it hasn't been installed on a process yet. I'm happy to see lockdep being added here, but can you elaborate on why add this mmap_locked_required instead of obtaining the lock in the execv path? Jason