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Tue, 16 Apr 2024 05:37:03 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id 60sFNX8OHmbNMQAAD6G6ig (envelope-from ); Tue, 16 Apr 2024 05:37:03 +0000 Date: Tue, 16 Apr 2024 07:36:58 +0200 From: Oscar Salvador To: Matthew Wilcox Cc: Vishal Moola , syzbot , akpm@linux-foundation.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, muchun.song@linux.dev, syzkaller-bugs@googlegroups.com Subject: Re: [syzbot] [mm?] KASAN: slab-use-after-free Read in __vma_reservation_common Message-ID: References: <000000000000daf1e10615e64dcb@google.com> <000000000000ae5d410615fea3bf@google.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: 2BC6D40002 X-Stat-Signature: du9cpsuebcaat6rgqn9eirodtqri9z9b X-HE-Tag: 1713245826-254758 X-HE-Meta: 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 BgO8HxRi Veg5Rk7VpVrFBC6D0Ywh+XdXaWnkR9OF6HUul7fBa7Ie3bplDmHaEfo4JcYDz+L/okyoXPoMp4yyW+oDxKfCIisPI1V4xd4kzTBcd 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: List-Subscribe: List-Unsubscribe: On Tue, Apr 16, 2024 at 05:35:50AM +0100, Matthew Wilcox wrote: > Why does hugetlbfs use VM_MAYSHARE while regular faults use VM_SHARED? It goes back to: commit f83a275dbc5ca1721143698e844243fcadfabf6a Author: Mel Gorman Date: Thu May 28 14:34:40 2009 -0700 mm: account for MAP_SHARED mappings using VM_MAYSHARE and not VM_SHARED in hugetlbfs "hugetlbfs currently checks if a VMA is MAP_SHARED with the VM_SHARED flag and not VM_MAYSHARE. For file-backed mappings, such as hugetlbfs, VM_SHARED is set only if the mapping is MAP_SHARED and the file was opened read-write. If a shared memory mapping was mapped shared-read-write for populating of data and mapped shared-read-only by other processes, then hugetlbfs would account for the mapping as if it was MAP_PRIVATE. This causes processes to fail to map the file MAP_SHARED even though it should succeed as the reservation is there." -- Oscar Salvador SUSE Labs