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Message-ID: <20220824100652.227m7eq4zqq7luir@quack3> Date: Wed, 24 Aug 2022 12:06:52 +0200 From: Jan Kara <jack@...e.cz> To: syzbot <syzbot+79e6bbabf3ce17357969@...kaller.appspotmail.com> Cc: jack@...e.com, linux-ext4@...r.kernel.org, linux-kernel@...r.kernel.org, syzkaller-bugs@...glegroups.com, tytso@....edu, Ye Bin <yebin10@...wei.com> Subject: Re: [syzbot] possible deadlock in jbd2_journal_lock_updates On Mon 08-08-22 09:38:26, syzbot wrote: > syzbot has found a reproducer for the following issue on: > > HEAD commit: ca688bff68bc Add linux-next specific files for 20220808 > git tree: linux-next > console+strace: https://syzkaller.appspot.com/x/log.txt?x=1143ed46080000 > kernel config: https://syzkaller.appspot.com/x/.config?x=4c20e006003cdecb > dashboard link: https://syzkaller.appspot.com/bug?extid=79e6bbabf3ce17357969 > compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2 > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1783be71080000 > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=12bcdbfa080000 > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > Reported-by: syzbot+79e6bbabf3ce17357969@...kaller.appspotmail.com > > warning: checkpointing journal with EXT4_IOC_CHECKPOINT_FLAG_ZEROOUT can be slow > ====================================================== > WARNING: possible circular locking dependency detected > 5.19.0-next-20220808-syzkaller #0 Not tainted > ------------------------------------------------------ > syz-executor677/3614 is trying to acquire lock: > ffff88814b8a4170 (&journal->j_barrier){+.+.}-{3:3}, at: jbd2_journal_lock_updates+0x15e/0x310 fs/jbd2/transaction.c:904 > > but task is already holding lock: > ffff88814b8a2bd8 (&sbi->s_writepages_rwsem){++++}-{0:0}, at: ext4_change_inode_journal_flag+0x178/0x530 fs/ext4/inode.c:6013 So this seems like a real issue. Essentially, the problem is that ext4_bmap() acquires inode->i_rwsem while its caller jbd2_journal_flush() is holding journal->j_checkpoint_mutex. This looks like a real deadlock possibility. This lock inversion was introduced by commit 51ae846cff5 ("ext4: fix warning in ext4_iomap_begin as race between bmap and write") which was fixing up a race in inline data handling. Thinking about it some more, it does not seem locking i_rwsem in ext4_bmap() is really workable and as I've noted in one of my replies to this patch [1] it is not a complete solution to the problem anyway. So I would be for reverting 51ae846cff5 and thinking more about how we can make inline data locking suck less... [1] https://lore.kernel.org/all/20220615172609.oydxhjw7exas23hd@quack3.lan/ Honza > which lock already depends on the new lock. > > > the existing dependency chain (in reverse order) is: > > -> #4 (&sbi->s_writepages_rwsem){++++}-{0:0}: > percpu_down_write+0x4d/0x440 kernel/locking/percpu-rwsem.c:221 > ext4_change_inode_journal_flag+0x178/0x530 fs/ext4/inode.c:6013 > ext4_ioctl_setflags fs/ext4/ioctl.c:685 [inline] > ext4_fileattr_set+0xddf/0x1930 fs/ext4/ioctl.c:1001 > vfs_fileattr_set+0x7f5/0xbe0 fs/ioctl.c:696 > ioctl_fssetxattr fs/ioctl.c:758 [inline] > do_vfs_ioctl+0xe62/0x15c0 fs/ioctl.c:845 > __do_sys_ioctl fs/ioctl.c:868 [inline] > __se_sys_ioctl fs/ioctl.c:856 [inline] > __x64_sys_ioctl+0x108/0x200 fs/ioctl.c:856 > do_syscall_x64 arch/x86/entry/common.c:50 [inline] > do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80 > entry_SYSCALL_64_after_hwframe+0x63/0xcd > > -> #3 (mapping.invalidate_lock){++++}-{3:3}: > down_write+0x90/0x150 kernel/locking/rwsem.c:1552 > filemap_invalidate_lock include/linux/fs.h:806 [inline] > ext4_setattr+0xd9e/0x2c50 fs/ext4/inode.c:5445 > notify_change+0xcd0/0x1440 fs/attr.c:418 > do_truncate+0x13c/0x200 fs/open.c:65 > do_sys_ftruncate+0x536/0x730 fs/open.c:193 > do_syscall_x64 arch/x86/entry/common.c:50 [inline] > do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80 > entry_SYSCALL_64_after_hwframe+0x63/0xcd > > -> #2 (&sb->s_type->i_mutex_key#8){++++}-{3:3}: > down_read+0x98/0x450 kernel/locking/rwsem.c:1499 > inode_lock_shared include/linux/fs.h:771 [inline] > ext4_bmap+0x4e/0x460 fs/ext4/inode.c:3157 > bmap+0xaa/0x120 fs/inode.c:1799 > jbd2_journal_bmap+0xa8/0x180 fs/jbd2/journal.c:971 > __jbd2_journal_erase fs/jbd2/journal.c:1784 [inline] > jbd2_journal_flush+0x84f/0xc00 fs/jbd2/journal.c:2490 > ext4_ioctl_checkpoint fs/ext4/ioctl.c:1082 [inline] > __ext4_ioctl+0x28fd/0x4ab0 fs/ext4/ioctl.c:1586 > vfs_ioctl fs/ioctl.c:51 [inline] > __do_sys_ioctl fs/ioctl.c:870 [inline] > __se_sys_ioctl fs/ioctl.c:856 [inline] > __x64_sys_ioctl+0x193/0x200 fs/ioctl.c:856 > do_syscall_x64 arch/x86/entry/common.c:50 [inline] > do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80 > entry_SYSCALL_64_after_hwframe+0x63/0xcd > > -> #1 (&journal->j_checkpoint_mutex){+.+.}-{3:3}: > __mutex_lock_common kernel/locking/mutex.c:603 [inline] > mutex_lock_io_nested+0x13f/0x1190 kernel/locking/mutex.c:833 > jbd2_journal_flush+0x19a/0xc00 fs/jbd2/journal.c:2462 > ext4_ioctl_checkpoint fs/ext4/ioctl.c:1082 [inline] > __ext4_ioctl+0x28fd/0x4ab0 fs/ext4/ioctl.c:1586 > vfs_ioctl fs/ioctl.c:51 [inline] > __do_sys_ioctl fs/ioctl.c:870 [inline] > __se_sys_ioctl fs/ioctl.c:856 [inline] > __x64_sys_ioctl+0x193/0x200 fs/ioctl.c:856 > do_syscall_x64 arch/x86/entry/common.c:50 [inline] > do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80 > entry_SYSCALL_64_after_hwframe+0x63/0xcd > > -> #0 (&journal->j_barrier){+.+.}-{3:3}: > check_prev_add kernel/locking/lockdep.c:3095 [inline] > check_prevs_add kernel/locking/lockdep.c:3214 [inline] > validate_chain kernel/locking/lockdep.c:3829 [inline] > __lock_acquire+0x2a43/0x56d0 kernel/locking/lockdep.c:5053 > lock_acquire kernel/locking/lockdep.c:5666 [inline] > lock_acquire+0x1ab/0x570 kernel/locking/lockdep.c:5631 > __mutex_lock_common kernel/locking/mutex.c:603 [inline] > __mutex_lock+0x12f/0x1350 kernel/locking/mutex.c:747 > jbd2_journal_lock_updates+0x15e/0x310 fs/jbd2/transaction.c:904 > ext4_change_inode_journal_flag+0x180/0x530 fs/ext4/inode.c:6014 > ext4_ioctl_setflags fs/ext4/ioctl.c:685 [inline] > ext4_fileattr_set+0xddf/0x1930 fs/ext4/ioctl.c:1001 > vfs_fileattr_set+0x7f5/0xbe0 fs/ioctl.c:696 > ioctl_fssetxattr fs/ioctl.c:758 [inline] > do_vfs_ioctl+0xe62/0x15c0 fs/ioctl.c:845 > __do_sys_ioctl fs/ioctl.c:868 [inline] > __se_sys_ioctl fs/ioctl.c:856 [inline] > __x64_sys_ioctl+0x108/0x200 fs/ioctl.c:856 > do_syscall_x64 arch/x86/entry/common.c:50 [inline] > do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80 > entry_SYSCALL_64_after_hwframe+0x63/0xcd > > other info that might help us debug this: > > Chain exists of: > &journal->j_barrier --> mapping.invalidate_lock --> &sbi->s_writepages_rwsem > > Possible unsafe locking scenario: > > CPU0 CPU1 > ---- ---- > lock(&sbi->s_writepages_rwsem); > lock(mapping.invalidate_lock); > lock(&sbi->s_writepages_rwsem); > lock(&journal->j_barrier); > > *** DEADLOCK *** > > 4 locks held by syz-executor677/3614: > #0: ffff88814b8a0460 (sb_writers#4){.+.+}-{0:0}, at: ioctl_setflags fs/ioctl.c:725 [inline] > #0: ffff88814b8a0460 (sb_writers#4){.+.+}-{0:0}, at: do_vfs_ioctl+0xe27/0x15c0 fs/ioctl.c:839 > #1: ffff88807599c030 (&sb->s_type->i_mutex_key#8){++++}-{3:3}, at: inode_lock include/linux/fs.h:761 [inline] > #1: ffff88807599c030 (&sb->s_type->i_mutex_key#8){++++}-{3:3}, at: vfs_fileattr_set+0x148/0xbe0 fs/ioctl.c:681 > #2: ffff88807599c1d0 (mapping.invalidate_lock){++++}-{3:3}, at: filemap_invalidate_lock include/linux/fs.h:806 [inline] > #2: ffff88807599c1d0 (mapping.invalidate_lock){++++}-{3:3}, at: ext4_change_inode_journal_flag+0x11f/0x530 fs/ext4/inode.c:6005 > #3: ffff88814b8a2bd8 (&sbi->s_writepages_rwsem){++++}-{0:0}, at: ext4_change_inode_journal_flag+0x178/0x530 fs/ext4/inode.c:6013 > > stack backtrace: > CPU: 0 PID: 3614 Comm: syz-executor677 Not tainted 5.19.0-next-20220808-syzkaller #0 > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/22/2022 > Call Trace: > <TASK> > __dump_stack lib/dump_stack.c:88 [inline] > dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106 > check_noncircular+0x25f/0x2e0 kernel/locking/lockdep.c:2175 > check_prev_add kernel/locking/lockdep.c:3095 [inline] > check_prevs_add kernel/locking/lockdep.c:3214 [inline] > validate_chain kernel/locking/lockdep.c:3829 [inline] > __lock_acquire+0x2a43/0x56d0 kernel/locking/lockdep.c:5053 > lock_acquire kernel/locking/lockdep.c:5666 [inline] > lock_acquire+0x1ab/0x570 kernel/locking/lockdep.c:5631 > __mutex_lock_common kernel/locking/mutex.c:603 [inline] > __mutex_lock+0x12f/0x1350 kernel/locking/mutex.c:747 > jbd2_journal_lock_updates+0x15e/0x310 fs/jbd2/transaction.c:904 > ext4_change_inode_journal_flag+0x180/0x530 fs/ext4/inode.c:6014 > ext4_ioctl_setflags fs/ext4/ioctl.c:685 [inline] > ext4_fileattr_set+0xddf/0x1930 fs/ext4/ioctl.c:1001 > vfs_fileattr_set+0x7f5/0xbe0 fs/ioctl.c:696 > ioctl_fssetxattr fs/ioctl.c:758 [inline] > do_vfs_ioctl+0xe62/0x15c0 fs/ioctl.c:845 > __do_sys_ioctl fs/ioctl.c:868 [inline] > __se_sys_ioctl fs/ioctl.c:856 [inline] > __x64_sys_ioctl+0x108/0x200 fs/ioctl.c:856 > do_syscall_x64 arch/x86/entry/common.c:50 [inline] > do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80 > entry_SYSCALL_64_after_hwframe+0x63/0xcd > RIP: 0033:0x7fb9f377eb39 > Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 e1 14 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 c0 ff ff ff f7 d8 64 89 01 48 > RSP: 002b:00007fffd29d1e18 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 > RAX: ffffffffffffffda RBX: 00007fffd29d1e58 RCX: 00007fb9f377eb39 > RDX: 0000000020000040 RSI: 0000000040086602 RDI: 0000000000000005 > RBP: 0000000000000000 R08: 431bde82d7b634db R09: 431bde82d7b634db > R10: 431bde82d7b634db R11: 0000000000000246 R12: 00007fb9f3741e40 > R13: 431bde82d7b634db R14: 00007fffd29d1e50 R15: 0000000000000000 > </TASK> > -- Jan Kara <jack@...e.com> SUSE Labs, CR
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