[Cc: Rafael] On Mon, 12 Feb 2024 at 11:36, syzbot <syzbot+af9aa785e14a67796a87@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote: > > Hello, > > syzbot found the following issue on: > > HEAD commit: 841c35169323 Linux 6.8-rc4 > git tree: upstream > console output: https://syzkaller.appspot.com/x/log.txt?x=1215e120180000 > kernel config: https://syzkaller.appspot.com/x/.config?x=fbd950b5071b7ea3 > dashboard link: https://syzkaller.appspot.com/bug?extid=af9aa785e14a67796a87 > compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40 > > Unfortunately, I don't have any reproducer for this issue yet. > > Downloadable assets: > disk image: https://storage.googleapis.com/syzbot-assets/ef821afd15d3/disk-841c3516.raw.xz > vmlinux: https://storage.googleapis.com/syzbot-assets/e41102f18e6e/vmlinux-841c3516.xz > kernel image: https://storage.googleapis.com/syzbot-assets/a17352b259d8/bzImage-841c3516.xz > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > Reported-by: syzbot+af9aa785e14a67796a87@xxxxxxxxxxxxxxxxxxxxxxxxx > > F2FS-fs (loop1): Found nat_bits in checkpoint > F2FS-fs (loop1): Mounted with checkpoint version = 48b305e5 > ====================================================== > WARNING: possible circular locking dependency detected > 6.8.0-rc4-syzkaller #0 Not tainted > ------------------------------------------------------ > syz-executor.1/640 is trying to acquire lock: > ffff888072750310 (&p->lock){+.+.}-{3:3}, at: seq_read_iter+0xb7/0xd60 fs/seq_file.c:182 > > but task is already holding lock: > ffff888023f61c68 (&pipe->mutex/1){+.+.}-{3:3}, at: splice_file_to_pipe+0x2e/0x500 fs/splice.c:1292 > > which lock already depends on the new lock. > > > the existing dependency chain (in reverse order) is: > > -> #4 (&pipe->mutex/1){+.+.}-{3:3}: > lock_acquire+0x1e3/0x530 kernel/locking/lockdep.c:5754 > __mutex_lock_common kernel/locking/mutex.c:608 [inline] > __mutex_lock+0x136/0xd70 kernel/locking/mutex.c:752 > iter_file_splice_write+0x335/0x14e0 fs/splice.c:687 > do_splice_from fs/splice.c:941 [inline] > do_splice+0xd77/0x1880 fs/splice.c:1354 > __do_splice fs/splice.c:1436 [inline] > __do_sys_splice fs/splice.c:1652 [inline] > __se_sys_splice+0x331/0x4a0 fs/splice.c:1634 > do_syscall_64+0xf9/0x240 > entry_SYSCALL_64_after_hwframe+0x6f/0x77 plain fs sb_writers --> pipe->mutex This is just a plain splice from a pipe to a regular file (which can be on the upper layer of overlayfs). > -> #3 (sb_writers#4){.+.+}-{0:0}: > lock_acquire+0x1e3/0x530 kernel/locking/lockdep.c:5754 > percpu_down_read include/linux/percpu-rwsem.h:51 [inline] > __sb_start_write include/linux/fs.h:1639 [inline] > sb_start_write+0x4d/0x1c0 include/linux/fs.h:1775 > mnt_want_write+0x3f/0x90 fs/namespace.c:409 > ovl_fix_origin fs/overlayfs/namei.c:908 [inline] > ovl_lookup+0x1394/0x2a60 fs/overlayfs/namei.c:1143 > __lookup_slow+0x28c/0x3f0 fs/namei.c:1693 > lookup_slow+0x53/0x70 fs/namei.c:1710 > walk_component fs/namei.c:2001 [inline] > link_path_walk+0x9cd/0xe80 fs/namei.c:2328 > path_lookupat+0xa9/0x450 fs/namei.c:2481 > filename_lookup+0x255/0x610 fs/namei.c:2511 > user_path_at_empty+0x42/0x60 fs/namei.c:2920 > user_path_at include/linux/namei.h:57 [inline] > __do_sys_chdir fs/open.c:556 [inline] > __se_sys_chdir+0xbf/0x220 fs/open.c:550 > do_syscall_64+0xf9/0x240 > entry_SYSCALL_64_after_hwframe+0x6f/0x77 overlayfs directory i_mutex --> plain fs sb_writers This is perfectly normal lock ordering for overlayfs: lock the overlayfs inode, then call mnt_want_write() on the upper filesystem. > -> #2 (&ovl_i_mutex_dir_key[depth]){++++}-{3:3}: > lock_acquire+0x1e3/0x530 kernel/locking/lockdep.c:5754 > down_read+0xb1/0xa40 kernel/locking/rwsem.c:1526 > inode_lock_shared include/linux/fs.h:812 [inline] > lookup_slow+0x45/0x70 fs/namei.c:17091 > walk_component+0x2e1/0x410 fs/namei.c:2001 > lookup_last fs/namei.c:2458 [inline] > path_lookupat+0x16f/0x450 fs/namei.c:2482 > filename_lookup+0x255/0x610 fs/namei.c:2511 > kern_path+0x35/0x50 fs/namei.c:2619 > lookup_bdev+0xc5/0x290 block/bdev.c:1014 > resume_store+0x1a0/0x710 kernel/power/hibernate.c:1183 > kernfs_fop_write_iter+0x3a4/0x500 fs/kernfs/file.c:334 > call_write_iter include/linux/fs.h:2085 [inline] > new_sync_write fs/read_write.c:497 [inline] > vfs_write+0xa81/0xcb0 fs/read_write.c:590 > ksys_write+0x1a0/0x2c0 fs/read_write.c:643 > do_syscall_64+0xf9/0x240 > entry_SYSCALL_64_after_hwframe+0x6f/0x77 kernfs of->mutex --> overlayfs directory i_mutex The device name is written to /sys/power/resume. When performing the lookup of the name, the inode lock is taken on the directory, which happens to be on overlayfs. > -> #1 (&of->mutex){+.+.}-{3:3}: > lock_acquire+0x1e3/0x530 kernel/locking/lockdep.c:5754 > __mutex_lock_common kernel/locking/mutex.c:608 [inline] > __mutex_lock+0x136/0xd70 kernel/locking/mutex.c:752 > kernfs_seq_start+0x53/0x3b0 fs/kernfs/file.c:154 > seq_read_iter+0x3d0/0xd60 fs/seq_file.c:225 > call_read_iter include/linux/fs.h:2079 [inline] > new_sync_read fs/read_write.c:395 [inline] > vfs_read+0x978/0xb70 fs/read_write.c:476 > ksys_read+0x1a0/0x2c0 fs/read_write.c:619 > do_syscall_64+0xf9/0x240 > entry_SYSCALL_64_after_hwframe+0x6f/0x77 seqfile p->lock --> kernfs of->mutex Reading an attribute. It could be "/sys/power/resume", but here we don't know, it's just the same lock class. > -> #0 (&p->lock){+.+.}-{3:3}: > check_prev_add kernel/locking/lockdep.c:3134 [inline] > check_prevs_add kernel/locking/lockdep.c:3253 [inline] > validate_chain+0x18ca/0x58e0 kernel/locking/lockdep.c:3869 > __lock_acquire+0x1345/0x1fd0 kernel/locking/lockdep.c:5137 > lock_acquire+0x1e3/0x530 kernel/locking/lockdep.c:5754 > __mutex_lock_common kernel/locking/mutex.c:608 [inline] > __mutex_lock+0x136/0xd70 kernel/locking/mutex.c:752 > seq_read_iter+0xb7/0xd60 fs/seq_file.c:182 > proc_reg_read_iter+0x1c3/0x290 fs/proc/inode.c:302 > call_read_iter include/linux/fs.h:2079 [inline] > copy_splice_read+0x661/0xb60 fs/splice.c:365 > do_splice_read fs/splice.c:985 [inline] > splice_file_to_pipe+0x299/0x500 fs/splice.c:1295 > do_sendfile+0x515/0xdc0 fs/read_write.c:1301 > __do_sys_sendfile64 fs/read_write.c:1356 [inline] > __se_sys_sendfile64+0x100/0x1e0 fs/read_write.c:1348 > do_syscall_64+0xf9/0x240 > entry_SYSCALL_64_after_hwframe+0x6f/0x77 pipe->mutex --> seqfile p->lock This is a sendfile from a seqfile. Could have been "/sys/power/resume" as well, AFAICS. I don't really know if/how this needs fixing, but that path lookup in resume_store() looks a bit nasty. Thanks, Miklos > > other info that might help us debug this: > > Chain exists of: > &p->lock --> sb_writers#4 --> &pipe->mutex/1 > > Possible unsafe locking scenario: > > CPU0 CPU1 > ---- ---- > lock(&pipe->mutex/1); > lock(sb_writers#4); > lock(&pipe->mutex/1); > lock(&p->lock); > > *** DEADLOCK *** > > 1 lock held by syz-executor.1/640: > #0: ffff888023f61c68 (&pipe->mutex/1){+.+.}-{3:3}, at: splice_file_to_pipe+0x2e/0x500 fs/splice.c:1292 > > stack backtrace: > CPU: 1 PID: 640 Comm: syz-executor.1 Not tainted 6.8.0-rc4-syzkaller #0 > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/25/2024 > Call Trace: > <TASK> > __dump_stack lib/dump_stack.c:88 [inline] > dump_stack_lvl+0x1e7/0x2e0 lib/dump_stack.c:106 > check_noncircular+0x36a/0x4a0 kernel/locking/lockdep.c:2187 > check_prev_add kernel/locking/lockdep.c:3134 [inline] > check_prevs_add kernel/locking/lockdep.c:3253 [inline] > validate_chain+0x18ca/0x58e0 kernel/locking/lockdep.c:3869 > __lock_acquire+0x1345/0x1fd0 kernel/locking/lockdep.c:5137 > lock_acquire+0x1e3/0x530 kernel/locking/lockdep.c:5754 > __mutex_lock_common kernel/locking/mutex.c:608 [inline] > __mutex_lock+0x136/0xd70 kernel/locking/mutex.c:752 > seq_read_iter+0xb7/0xd60 fs/seq_file.c:182 > proc_reg_read_iter+0x1c3/0x290 fs/proc/inode.c:302 > call_read_iter include/linux/fs.h:2079 [inline] > copy_splice_read+0x661/0xb60 fs/splice.c:365 > do_splice_read fs/splice.c:985 [inline] > splice_file_to_pipe+0x299/0x500 fs/splice.c:1295 > do_sendfile+0x515/0xdc0 fs/read_write.c:1301 > __do_sys_sendfile64 fs/read_write.c:1356 [inline] > __se_sys_sendfile64+0x100/0x1e0 fs/read_write.c:1348 > do_syscall_64+0xf9/0x240 > entry_SYSCALL_64_after_hwframe+0x6f/0x77 > RIP: 0033:0x7f3acde7dda9 > Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 e1 20 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b0 ff ff ff f7 d8 64 89 01 48 > RSP: 002b:00007f3acec5e0c8 EFLAGS: 00000246 ORIG_RAX: 0000000000000028 > RAX: ffffffffffffffda RBX: 00007f3acdfac050 RCX: 00007f3acde7dda9 > RDX: 0000000020000000 RSI: 0000000000000004 RDI: 0000000000000000 > RBP: 00007f3acdeca47a R08: 0000000000000000 R09: 0000000000000000 > R10: 0000000000000007 R11: 0000000000000246 R12: 0000000000000000 > R13: 000000000000000b R14: 00007f3acdfac050 R15: 00007fff9463d788 > </TASK> > > > --- > This report is generated by a bot. It may contain errors. > See https://goo.gl/tpsmEJ for more information about syzbot. > syzbot engineers can be reached at syzkaller@xxxxxxxxxxxxxxxx. > > syzbot will keep track of this issue. See: > https://goo.gl/tpsmEJ#status for how to communicate with syzbot. > > If the report is already addressed, let syzbot know by replying with: > #syz fix: exact-commit-title > > If you want to overwrite report's subsystems, reply with: > #syz set subsystems: new-subsystem > (See the list of subsystem names on the web dashboard) > > If the report is a duplicate of another one, reply with: > #syz dup: exact-subject-of-another-report > > If you want to undo deduplication, reply with: > #syz undup
