[syzbot] possible deadlock in __nilfs_error

From: syzbot
Date: Sat Oct 15 2022 - 15:22:55 EST

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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@xxxxxxxxxxxxxxxxxxxxxxxxx

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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Next message: Vlastimil Babka: "Re: [PATCH v4 10/17] mm/slab: kmalloc: pass requests larger than order-1 page to page allocator"
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