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Tue, 4 Mar 2025 11:06:59 +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 qSUjENPexmefbgAAD6G6ig (envelope-from ); Tue, 04 Mar 2025 11:06:59 +0000 Received: by quack3.suse.cz (Postfix, from userid 1000) id 05DA3A0912; Tue, 4 Mar 2025 12:06:58 +0100 (CET) Date: Tue, 4 Mar 2025 12:06:58 +0100 From: Jan Kara To: syzbot Cc: akpm@linux-foundation.org, amir73il@gmail.com, axboe@kernel.dk, brauner@kernel.org, cem@kernel.org, chandan.babu@oracle.com, djwong@kernel.org, jack@suse.cz, josef@toxicpanda.com, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-xfs@vger.kernel.org, syzkaller-bugs@googlegroups.com Subject: Re: [syzbot] [xfs?] WARNING in fsnotify_file_area_perm Message-ID: <7ehxrhbvehlrjwvrduoxsao5k3x4aw275patsb3krkwuq573yv@o2hskrfawbnc> References: <67a487f7.050a0220.19061f.05fc.GAE@google.com> <67c4881e.050a0220.1dee4d.0054.GAE@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <67c4881e.050a0220.1dee4d.0054.GAE@google.com> X-Rspamd-Action: no action X-Stat-Signature: k61seo8pwq4ukeojnw68jqug7bnkp33e X-Rspamd-Queue-Id: 0BBA540021 X-Rspamd-Server: rspam06 X-Rspam-User: X-HE-Tag: 1741086420-940638 X-HE-Meta: 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 4dp4RRWp 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 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: Josef, Amir, this is indeed an interesting case: On Sun 02-03-25 08:32:30, syzbot wrote: > syzbot has found a reproducer for the following issue on: ... > ------------[ cut here ]------------ > WARNING: CPU: 1 PID: 6440 at ./include/linux/fsnotify.h:145 fsnotify_file_area_perm+0x20c/0x25c include/linux/fsnotify.h:145 > Modules linked in: > CPU: 1 UID: 0 PID: 6440 Comm: syz-executor370 Not tainted 6.14.0-rc4-syzkaller-ge056da87c780 #0 > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 12/27/2024 > pstate: 80400005 (Nzcv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--) > pc : fsnotify_file_area_perm+0x20c/0x25c include/linux/fsnotify.h:145 > lr : fsnotify_file_area_perm+0x20c/0x25c include/linux/fsnotify.h:145 > sp : ffff8000a42569d0 > x29: ffff8000a42569d0 x28: ffff0000dcec1b48 x27: ffff0000d68a1708 > x26: ffff0000d68a16c0 x25: dfff800000000000 x24: 0000000000008000 > x23: 0000000000000001 x22: ffff8000a4256b00 x21: 0000000000001000 > x20: 0000000000000010 x19: ffff0000d68a16c0 x18: ffff8000a42566e0 > x17: 000000000000e388 x16: ffff800080466c24 x15: 0000000000000001 > x14: 1fffe0001b31513c x13: 0000000000000000 x12: 0000000000000000 > x11: 0000000000000001 x10: 0000000000ff0100 x9 : 0000000000000000 > x8 : ffff0000c6d98000 x7 : 0000000000000000 x6 : 0000000000000000 > x5 : 0000000000000020 x4 : 0000000000000000 x3 : 0000000000001000 > x2 : ffff8000a4256b00 x1 : 0000000000000001 x0 : 0000000000000000 > Call trace: > fsnotify_file_area_perm+0x20c/0x25c include/linux/fsnotify.h:145 (P) > filemap_fault+0x12b0/0x1518 mm/filemap.c:3509 > xfs_filemap_fault+0xc4/0x194 fs/xfs/xfs_file.c:1543 > __do_fault+0xf8/0x498 mm/memory.c:4988 > do_read_fault mm/memory.c:5403 [inline] > do_fault mm/memory.c:5537 [inline] > do_pte_missing mm/memory.c:4058 [inline] > handle_pte_fault+0x3504/0x57b0 mm/memory.c:5900 > __handle_mm_fault mm/memory.c:6043 [inline] > handle_mm_fault+0xfa8/0x188c mm/memory.c:6212 > do_page_fault+0x570/0x10a8 arch/arm64/mm/fault.c:690 > do_translation_fault+0xc4/0x114 arch/arm64/mm/fault.c:783 > do_mem_abort+0x74/0x200 arch/arm64/mm/fault.c:919 > el1_abort+0x3c/0x5c arch/arm64/kernel/entry-common.c:432 > el1h_64_sync_handler+0x60/0xcc arch/arm64/kernel/entry-common.c:510 > el1h_64_sync+0x6c/0x70 arch/arm64/kernel/entry.S:595 > __uaccess_mask_ptr arch/arm64/include/asm/uaccess.h:169 [inline] (P) > fault_in_readable+0x168/0x310 mm/gup.c:2234 (P) > fault_in_iov_iter_readable+0x1dc/0x22c lib/iov_iter.c:94 > iomap_write_iter fs/iomap/buffered-io.c:950 [inline] > iomap_file_buffered_write+0x490/0xd54 fs/iomap/buffered-io.c:1039 > xfs_file_buffered_write+0x2dc/0xac8 fs/xfs/xfs_file.c:792 > xfs_file_write_iter+0x2c4/0x6ac fs/xfs/xfs_file.c:881 > new_sync_write fs/read_write.c:586 [inline] > vfs_write+0x704/0xa9c fs/read_write.c:679 The backtrace actually explains it all. We had a buffered write whose buffer was mmapped file on a filesystem with an HSM mark. Now the prefaulting of the buffer happens already (quite deep) under the filesystem freeze protection (obtained in vfs_write()) which breaks assumptions of HSM code and introduces potential deadlock of HSM handler in userspace with filesystem freezing. So we need to think how to deal with this case... Honza -- Jan Kara SUSE Labs, CR