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Date:   Sat, 15 Oct 2022 12:22:42 -0700
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Subject: [syzbot] possible deadlock in __nilfs_error
From:   syzbot <syzbot+3a94da2c82ba4f401b9e@syzkaller.appspotmail.com>
To:     konishi.ryusuke@gmail.com, linux-kernel@vger.kernel.org,
        linux-nilfs@vger.kernel.org, syzkaller-bugs@googlegroups.com
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Hello,

syzbot found the following issue on:

HEAD commit:    bbed346d5a96 Merge branch 'for-next/core' into for-kernelci
git tree:       git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci
console output: https://syzkaller.appspot.com/x/log.txt?x=12497f8a880000
kernel config:  https://syzkaller.appspot.com/x/.config?x=3a4a45d2d827c1e
dashboard link: https://syzkaller.appspot.com/bug?extid=3a94da2c82ba4f401b9e
compiler:       Debian clang version 13.0.1-++20220126092033+75e33f71c2da-1~exp1~20220126212112.63, GNU ld (GNU Binutils for Debian) 2.35.2
userspace arch: arm64

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/e8e91bc79312/disk-bbed346d.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/c1cb3fb3b77e/vmlinux-bbed346d.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+3a94da2c82ba4f401b9e@syzkaller.appspotmail.com

WARNING: possible circular locking dependency detected
6.0.0-rc7-syzkaller-18095-gbbed346d5a96 #0 Not tainted
------------------------------------------------------
syz-executor.5/28633 is trying to acquire lock:
ffff0001126ee890 (&nilfs->ns_sem){++++}-{3:3}, at: nilfs_set_error fs/nilfs2/super.c:92 [inline]
ffff0001126ee890 (&nilfs->ns_sem){++++}-{3:3}, at: __nilfs_error+0xb4/0x284 fs/nilfs2/super.c:137

but task is already holding lock:
ffff000123b51e70 (&dat_lock_key
){.+.+}-{3:3}, at: nilfs_get_block+0x64/0x364 fs/nilfs2/inode.c:84

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (&dat_lock_key){.+.+}-{3:3}:
       down_read+0x5c/0x78 kernel/locking/rwsem.c:1499
       nilfs_count_free_blocks+0x2c/0x6c fs/nilfs2/the_nilfs.c:693
       nilfs_set_log_cursor fs/nilfs2/super.c:236 [inline]
       nilfs_cleanup_super+0x118/0x1f0 fs/nilfs2/super.c:318
       nilfs_put_super+0x54/0x9c fs/nilfs2/super.c:472
       generic_shutdown_super+0x8c/0x190 fs/super.c:491
       kill_block_super+0x30/0x78 fs/super.c:1427
       deactivate_locked_super+0x70/0xe8 fs/super.c:332
       deactivate_super+0xd0/0xd4 fs/super.c:363
       cleanup_mnt+0x1f8/0x234 fs/namespace.c:1186
       __cleanup_mnt+0x20/0x30 fs/namespace.c:1193
       task_work_run+0xc4/0x14c kernel/task_work.c:177
       resume_user_mode_work include/linux/resume_user_mode.h:49 [inline]
       do_notify_resume+0x174/0x1f0 arch/arm64/kernel/signal.c:1127
       prepare_exit_to_user_mode arch/arm64/kernel/entry-common.c:137 [inline]
       exit_to_user_mode arch/arm64/kernel/entry-common.c:142 [inline]
       el0_svc+0x9c/0x150 arch/arm64/kernel/entry-common.c:637
       el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:654
       el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:581

-> #0 (&nilfs->ns_sem){++++}-{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+0x1530/0x30a4 kernel/locking/lockdep.c:5053
       lock_acquire+0x100/0x1f8 kernel/locking/lockdep.c:5666
       down_write+0x5c/0xcc kernel/locking/rwsem.c:1552
       nilfs_set_error fs/nilfs2/super.c:92 [inline]
       __nilfs_error+0xb4/0x284 fs/nilfs2/super.c:137
       nilfs_bmap_convert_error fs/nilfs2/bmap.c:35 [inline]
       nilfs_bmap_lookup_contig+0x98/0xc0 fs/nilfs2/bmap.c:95
       nilfs_get_block+0x7c/0x364 fs/nilfs2/inode.c:85
       block_truncate_page+0x1b4/0xab4 fs/buffer.c:2583
       nilfs_truncate+0xb8/0x178 fs/nilfs2/inode.c:857
       nilfs_setattr+0xf8/0x164 fs/nilfs2/inode.c:955
       notify_change+0x758/0x7f0 fs/attr.c:420
       do_truncate+0x108/0x150 fs/open.c:65
       vfs_truncate+0x1dc/0x24c fs/open.c:111
       do_sys_truncate+0x94/0x140 fs/open.c:134
       __do_sys_truncate fs/open.c:146 [inline]
       __se_sys_truncate fs/open.c:144 [inline]
       __arm64_sys_truncate+0x20/0x30 fs/open.c:144
       __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
       invoke_syscall arch/arm64/kernel/syscall.c:52 [inline]
       el0_svc_common+0x138/0x220 arch/arm64/kernel/syscall.c:142
       do_el0_svc+0x48/0x164 arch/arm64/kernel/syscall.c:206
       el0_svc+0x58/0x150 arch/arm64/kernel/entry-common.c:636
       el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:654
       el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:581

other info that might help us debug this:

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&dat_lock_key);
                               lock(&nilfs->ns_sem);
                               lock(&dat_lock_key);
  lock(&nilfs->ns_sem);

 *** DEADLOCK ***

5 locks held by syz-executor.5/28633:
 #0: ffff0001199e2460 (sb_writers#16){.+.+}-{0:0}, at: mnt_want_write+0x20/0x64 fs/namespace.c:393
 #1: ffff0001128b2648 (&sb->s_type->i_mutex_key#26){+.+.}-{3:3}, at: inode_lock include/linux/fs.h:756 [inline]
 #1: ffff0001128b2648 (&sb->s_type->i_mutex_key#26){+.+.}-{3:3}, at: do_truncate+0xf4/0x150 fs/open.c:63
 #2: ffff0001199e2650 (sb_internal#3){.+.+}-{0:0}, at: nilfs_setattr+0x84/0x164 fs/nilfs2/inode.c:947
 #3: ffff0001126eeaa0 (&nilfs->ns_segctor_sem){++++}-{3:3}, at: nilfs_transaction_begin+0x214/0x384 fs/nilfs2/segment.c:223
 #4: ffff000123b51e70 (&dat_lock_key){.+.+}-{3:3}, at: nilfs_get_block+0x64/0x364 fs/nilfs2/inode.c:84

stack backtrace:
CPU: 1 PID: 28633 Comm: syz-executor.5 Not tainted 6.0.0-rc7-syzkaller-18095-gbbed346d5a96 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/30/2022
Call trace:
 dump_backtrace+0x1c4/0x1f0 arch/arm64/kernel/stacktrace.c:156
 show_stack+0x2c/0x54 arch/arm64/kernel/stacktrace.c:163
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x104/0x16c lib/dump_stack.c:106
 dump_stack+0x1c/0x58 lib/dump_stack.c:113
 print_circular_bug+0x2c4/0x2c8 kernel/locking/lockdep.c:2053
 check_noncircular+0x14c/0x154 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+0x1530/0x30a4 kernel/locking/lockdep.c:5053
 lock_acquire+0x100/0x1f8 kernel/locking/lockdep.c:5666
 down_write+0x5c/0xcc kernel/locking/rwsem.c:1552
 nilfs_set_error fs/nilfs2/super.c:92 [inline]
 __nilfs_error+0xb4/0x284 fs/nilfs2/super.c:137
 nilfs_bmap_convert_error fs/nilfs2/bmap.c:35 [inline]
 nilfs_bmap_lookup_contig+0x98/0xc0 fs/nilfs2/bmap.c:95
 nilfs_get_block+0x7c/0x364 fs/nilfs2/inode.c:85
 block_truncate_page+0x1b4/0xab4 fs/buffer.c:2583
 nilfs_truncate+0xb8/0x178 fs/nilfs2/inode.c:857
 nilfs_setattr+0xf8/0x164 fs/nilfs2/inode.c:955
 notify_change+0x758/0x7f0 fs/attr.c:420
 do_truncate+0x108/0x150 fs/open.c:65
 vfs_truncate+0x1dc/0x24c fs/open.c:111
 do_sys_truncate+0x94/0x140 fs/open.c:134
 __do_sys_truncate fs/open.c:146 [inline]
 __se_sys_truncate fs/open.c:144 [inline]
 __arm64_sys_truncate+0x20/0x30 fs/open.c:144
 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
 invoke_syscall arch/arm64/kernel/syscall.c:52 [inline]
 el0_svc_common+0x138/0x220 arch/arm64/kernel/syscall.c:142
 do_el0_svc+0x48/0x164 arch/arm64/kernel/syscall.c:206
 el0_svc+0x58/0x150 arch/arm64/kernel/entry-common.c:636
 el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:654
 el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:581
Remounting filesystem read-only
NILFS (loop5): bad btree node (ino=16, blocknr=15): level = 0, flags = 0x0, nchildren = 0
NILFS error (device loop5): nilfs_bmap_last_key: broken bmap (inode number=16)
NILFS (loop5): error -5 truncating bmap (ino=16)


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