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[172.10.233.147]) by smtp.gmail.com with ESMTPSA id f13sm4792637qkk.107.2021.06.04.15.35.24 (version=TLS1 cipher=ECDHE-ECDSA-AES128-SHA bits=128/128); Fri, 04 Jun 2021 15:35:26 -0700 (PDT) Date: Fri, 4 Jun 2021 15:35:24 -0700 (PDT) From: Hugh Dickins X-X-Sender: hugh@eggly.anvils To: Matthew Wilcox cc: Hugh Dickins , Andrew Morton , "Kirill A. Shutemov" , Yang Shi , Wang Yugui , Naoya Horiguchi , Alistair Popple , Ralph Campbell , Zi Yan , Miaohe Lin , Minchan Kim , Jue Wang , Peter Xu , Jan Kara , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 3/7] mm/thp: fix vma_address() if virtual address below file offset In-Reply-To: Message-ID: References: User-Agent: Alpine 2.11 (LSU 23 2013-08-11) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: F1833C0237E7 X-Stat-Signature: 97534e14rinc7srrn94uwmgqyiy1op1j Authentication-Results: imf22.hostedemail.com; dkim=pass header.d=google.com header.s=20161025 header.b="X/4CL2PG"; dmarc=pass (policy=reject) header.from=google.com; spf=pass (imf22.hostedemail.com: domain of hughd@google.com designates 209.85.160.181 as permitted sender) smtp.mailfrom=hughd@google.com X-HE-Tag: 1622875534-864170 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 Fri, 4 Jun 2021, Matthew Wilcox wrote: > On Thu, Jun 03, 2021 at 02:40:30PM -0700, Hugh Dickins wrote: > > static inline unsigned long > > -__vma_address(struct page *page, struct vm_area_struct *vma) > > +vma_address(struct page *page, struct vm_area_struct *vma) > > { > > - pgoff_t pgoff = page_to_pgoff(page); > > - return vma->vm_start + ((pgoff - vma->vm_pgoff) << PAGE_SHIFT); > > + pgoff_t pgoff; > > + unsigned long address; > > + > > + VM_BUG_ON_PAGE(PageKsm(page), page); /* KSM page->index unusable */ > > + pgoff = page_to_pgoff(page); > > + if (pgoff >= vma->vm_pgoff) { > > + address = vma->vm_start + > > + ((pgoff - vma->vm_pgoff) << PAGE_SHIFT); > > + /* Check for address beyond vma (or wrapped through 0?) */ > > + if (address < vma->vm_start || address >= vma->vm_end) > > + address = -EFAULT; > > + } else if (PageHead(page) && > > + pgoff + compound_nr(page) > vma->vm_pgoff) { > > I think on 32-bit, you need ... > > pgoff + compound_nr(page) - 1 >= vma->vm_pgoff > > ... right? Hey, beating me at my own game ;-) I'm pretty sure you're right (and it's true that I first wrote this patch before becoming conscious of the 32-bit MAX_LFS_FILESIZE issue); but caution tells me to think some more and check some places before committing to that. Thanks, Hugh