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[209.85.208.173]) by smtp.gmail.com with ESMTPSA id q3sm635025lff.42.2019.01.23.12.35.49 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 23 Jan 2019 12:35:49 -0800 (PST) Received: by mail-lj1-f173.google.com with SMTP id t18-v6so3186856ljd.4 for ; Wed, 23 Jan 2019 12:35:49 -0800 (PST) X-Received: by 2002:a2e:880a:: with SMTP id x10-v6mr3388044ljh.174.1548275749194; Wed, 23 Jan 2019 12:35:49 -0800 (PST) MIME-Version: 1.0 References: <20190110004424.GH27534@dastard> <20190110070355.GJ27534@dastard> <20190110122442.GA21216@nautica> <5c3e7de6.1c69fb81.4aebb.3fec@mx.google.com> <9E337EA6-7CDA-457B-96C6-E91F83742587@amacapital.net> <20190116054613.GA11670@nautica> In-Reply-To: From: Linus Torvalds Date: Thu, 24 Jan 2019 09:35:32 +1300 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH] mm/mincore: allow for making sys_mincore() privileged To: Jiri Kosina Cc: Dominique Martinet , Andy Lutomirski , Josh Snyder , Dave Chinner , Matthew Wilcox , Jann Horn , Andrew Morton , Greg KH , Peter Zijlstra , Michal Hocko , Linux-MM , kernel list , Linux API Content-Type: text/plain; charset="UTF-8" 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: Message-ID: <20190123203532.kJbtBYBKlZz2Q6ES1QW0OhvQykvpswqLXsRxegXQpLo@z> On Thu, Jan 24, 2019 at 9:27 AM Linus Torvalds wrote: > > I've reverted the 'let's try to just remove the code' part in my tree. > But I didn't apply the two other patches yet. Any final comments > before that should happen? Side note: the inode_permission() addition to can_do_mincore() in that patch 0002, seems to be questionable. We do +static inline bool can_do_mincore(struct vm_area_struct *vma) +{ + return vma_is_anonymous(vma) + || (vma->vm_file && (vma->vm_file->f_mode & FMODE_WRITE)) + || inode_permission(file_inode(vma->vm_file), MAY_WRITE) == 0; +} note how it tests whether vma->vm_file is NULL for the FMODE_WRITE test, but not for the inode_permission() test. So either we test unnecessarily in the second line, or we don't properly test it in the third one. I think the "test vm_file" thing may be unnecessary, because a non-anonymous mapping should always have a file pointer and an inode. But I could imagine some odd case (vdso mapping, anyone?) that doesn't have a vm_file, but also isn't anonymous. Anybody? Anyway, it's one reason why I didn't actually apply those other two patches yet. This may be a 5.1 issue.. Linus