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Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1pmbOO-006w6x-Bc; Wed, 12 Apr 2023 14:24:12 +0000 Date: Wed, 12 Apr 2023 15:24:12 +0100 From: Matthew Wilcox To: Tetsuo Handa Cc: syzbot , ntfs3@lists.linux.dev, syzkaller-bugs@googlegroups.com, Konstantin Komarov , Hillf Danton , linux-fsdevel , linux-mm , trix@redhat.com, ndesaulniers@google.com, nathan@kernel.org Subject: Re: [PATCH] fs/ntfs3: disable page fault during ntfs_fiemap() Message-ID: References: <000000000000e2102c05eeaf9113@google.com> <00000000000031b80705ef5d33d1@google.com> <60f6bb85-825c-95e2-79b8-25a2d0e9979e@I-love.SAKURA.ne.jp> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <60f6bb85-825c-95e2-79b8-25a2d0e9979e@I-love.SAKURA.ne.jp> X-Rspamd-Queue-Id: A98A540011 X-Stat-Signature: re9ag8buhgxqw8hyu795ndqrz4sb9kch X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1681309471-198977 X-HE-Meta: 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 8lljXYWl ASTW1v53bYQ8WamxaRkEDb4cD1+5V6rbuFhHbwSs3OywLjAmmRTqSAYn9wCdBSd7iXHNZjdA8dfTH6D48Sa8JKsoN7WVPWcMM2sJExelubeHunl6fpfydmNYFFg3a2BSClUCBRezGtHpW+jz79wKPwhoTKmpyoBf44sFq6SqarhhU4S7wN4deELih6pC8nKdsv8qm3BYrAQjB0hrA8mZepVkLVrjQPvDczSm8KXGnVcfnJZBokJifMZ0PfsfX79JufR4KnX8wlEEuWx+ZuNCpJvcuVkR9ZZa3BM10MJW79vkPn+A= 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 Wed, Apr 12, 2023 at 10:29:37PM +0900, Tetsuo Handa wrote: > On 2023/04/12 22:13, Matthew Wilcox wrote: > >> Also, since Documentation/filesystems/fiemap.rst says that "If an error > >> is encountered while copying the extent to user memory, -EFAULT will be > >> returned.", I assume that ioctl(FS_IOC_FIEMAP) users can handle -EFAULT > >> error. > > > > What? No, that doesn't mean "You can return -EFAULT because random luck". > > That means "If you pass it an invalid address, you'll get -EFAULT back". > > > > NACK. > > Then, why does fiemap.rst say "If an error is encountered" rather than > "If an invalid address is passed" ? Because people are bad at writing. > Does the definition of -EFAULT limited to "the caller does not have permission > to access this address" ? Or the address isn't mapped. > If copy_to_user() must not fail other than "the caller does not have > permission to access this address", what should we do for now? > Just remove ntfs_fiemap() and return -EOPNOTSUPP ? No, fix it properly. Or don't fix it at all and let somebody else fix it.