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Message-ID: <681cda41.050a0220.a19a9.0118.GAE@google.com>
Date: Thu, 08 May 2025 09:22:25 -0700
From: syzbot <syzbot+81394db39b0e2ed2db06@...kaller.appspotmail.com>
To: konishi.ryusuke@...il.com, linux-kernel@...r.kernel.org,
linux-nilfs@...r.kernel.org, syzkaller-bugs@...glegroups.com
Subject: [syzbot] [nilfs?] possible deadlock in nilfs_segctor_construct
Hello,
syzbot found the following issue on:
HEAD commit: e8ab83e34bdc Merge tag 'arm64-fixes' of git://git.kernel.o..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=146e70f4580000
kernel config: https://syzkaller.appspot.com/x/.config?x=a9a25b7a36123454
dashboard link: https://syzkaller.appspot.com/bug?extid=81394db39b0e2ed2db06
compiler: Debian clang version 20.1.2 (++20250402124445+58df0ef89dd6-1~exp1~20250402004600.97), Debian LLD 20.1.2
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=148c9a70580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1530b8d4580000
Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/7feb34a89c2a/non_bootable_disk-e8ab83e3.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/b26f15c51ac7/vmlinux-e8ab83e3.xz
kernel image: https://storage.googleapis.com/syzbot-assets/05e91bf788d8/bzImage-e8ab83e3.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/09efd3b532ea/mount_0.gz
IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+81394db39b0e2ed2db06@...kaller.appspotmail.com
======================================================
WARNING: possible circular locking dependency detected
6.15.0-rc4-syzkaller-00296-ge8ab83e34bdc #0 Not tainted
------------------------------------------------------
segctord/5299 is trying to acquire lock:
ffff88801189e090 (&nilfs->ns_sem){++++}-{4:4}, at: nilfs_segctor_construct+0x2b1/0x690 fs/nilfs2/segment.c:2485
but task is already holding lock:
ffff88801189e2a0 (&nilfs->ns_segctor_sem){++++}-{4:4}, at: nilfs_transaction_lock+0x253/0x4c0 fs/nilfs2/segment.c:357
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #5 (&nilfs->ns_segctor_sem){++++}-{4:4}:
lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5866
down_read+0x46/0x2e0 kernel/locking/rwsem.c:1524
nilfs_transaction_begin+0x365/0x710 fs/nilfs2/segment.c:221
nilfs_create+0xc9/0x2f0 fs/nilfs2/namei.c:95
lookup_open fs/namei.c:3701 [inline]
open_last_lookups fs/namei.c:3800 [inline]
path_openat+0x14f1/0x3830 fs/namei.c:4036
do_filp_open+0x1fa/0x410 fs/namei.c:4066
do_sys_openat2+0x121/0x1c0 fs/open.c:1429
do_sys_open fs/open.c:1444 [inline]
__do_sys_openat fs/open.c:1460 [inline]
__se_sys_openat fs/open.c:1455 [inline]
__x64_sys_openat+0x138/0x170 fs/open.c:1455
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xf6/0x210 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
-> #4 (sb_internal#2){.+.+}-{0:0}:
lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5866
percpu_down_read include/linux/percpu-rwsem.h:52 [inline]
__sb_start_write include/linux/fs.h:1783 [inline]
sb_start_intwrite include/linux/fs.h:1966 [inline]
nilfs_transaction_begin+0x268/0x710 fs/nilfs2/segment.c:218
nilfs_page_mkwrite+0x8b0/0xc20 fs/nilfs2/file.c:95
do_page_mkwrite+0x14a/0x310 mm/memory.c:3287
do_shared_fault mm/memory.c:5594 [inline]
do_fault mm/memory.c:5656 [inline]
do_pte_missing mm/memory.c:4160 [inline]
handle_pte_fault mm/memory.c:5997 [inline]
__handle_mm_fault+0x18d2/0x5380 mm/memory.c:6140
handle_mm_fault+0x3f6/0x8c0 mm/memory.c:6309
do_user_addr_fault+0x764/0x1390 arch/x86/mm/fault.c:1388
handle_page_fault arch/x86/mm/fault.c:1480 [inline]
exc_page_fault+0x68/0x110 arch/x86/mm/fault.c:1538
asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:623
-> #3 (sb_pagefaults){.+.+}-{0:0}:
lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5866
percpu_down_read include/linux/percpu-rwsem.h:52 [inline]
__sb_start_write include/linux/fs.h:1783 [inline]
sb_start_pagefault include/linux/fs.h:1948 [inline]
nilfs_page_mkwrite+0x21e/0xc20 fs/nilfs2/file.c:57
do_page_mkwrite+0x14a/0x310 mm/memory.c:3287
do_shared_fault mm/memory.c:5594 [inline]
do_fault mm/memory.c:5656 [inline]
do_pte_missing mm/memory.c:4160 [inline]
handle_pte_fault mm/memory.c:5997 [inline]
__handle_mm_fault+0x18d2/0x5380 mm/memory.c:6140
handle_mm_fault+0x3f6/0x8c0 mm/memory.c:6309
do_user_addr_fault+0x764/0x1390 arch/x86/mm/fault.c:1388
handle_page_fault arch/x86/mm/fault.c:1480 [inline]
exc_page_fault+0x68/0x110 arch/x86/mm/fault.c:1538
asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:623
-> #2 (&mm->mmap_lock){++++}-{4:4}:
lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5866
__might_fault+0xcc/0x130 mm/memory.c:7151
_copy_to_iter+0xf3/0x15a0 lib/iov_iter.c:184
copy_page_to_iter+0xa7/0x150 lib/iov_iter.c:362
copy_folio_to_iter include/linux/uio.h:198 [inline]
filemap_read+0x78d/0x11d0 mm/filemap.c:2753
blkdev_read_iter+0x30a/0x440 block/fops.c:809
new_sync_read fs/read_write.c:489 [inline]
vfs_read+0x4cd/0x980 fs/read_write.c:570
ksys_read+0x145/0x250 fs/read_write.c:713
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xf6/0x210 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
-> #1 (&sb->s_type->i_mutex_key#8){++++}-{4:4}:
lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5866
down_write+0x96/0x1f0 kernel/locking/rwsem.c:1577
inode_lock include/linux/fs.h:867 [inline]
set_blocksize+0x23b/0x500 block/bdev.c:203
sb_set_blocksize block/bdev.c:224 [inline]
sb_min_blocksize+0x119/0x210 block/bdev.c:239
init_nilfs+0x43/0x690 fs/nilfs2/the_nilfs.c:710
nilfs_fill_super+0x8f/0x650 fs/nilfs2/super.c:1060
nilfs_get_tree+0x4f4/0x870 fs/nilfs2/super.c:1228
vfs_get_tree+0x8f/0x2b0 fs/super.c:1759
do_new_mount+0x24a/0xa40 fs/namespace.c:3884
do_mount fs/namespace.c:4224 [inline]
__do_sys_mount fs/namespace.c:4435 [inline]
__se_sys_mount+0x317/0x410 fs/namespace.c:4412
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xf6/0x210 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
-> #0 (&nilfs->ns_sem){++++}-{4:4}:
check_prev_add kernel/locking/lockdep.c:3166 [inline]
check_prevs_add kernel/locking/lockdep.c:3285 [inline]
validate_chain+0xb9b/0x2140 kernel/locking/lockdep.c:3909
__lock_acquire+0xaac/0xd20 kernel/locking/lockdep.c:5235
lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5866
down_write+0x96/0x1f0 kernel/locking/rwsem.c:1577
nilfs_segctor_construct+0x2b1/0x690 fs/nilfs2/segment.c:2485
nilfs_segctor_thread_construct fs/nilfs2/segment.c:2586 [inline]
nilfs_segctor_thread+0x6f7/0xe00 fs/nilfs2/segment.c:2700
kthread+0x70e/0x8a0 kernel/kthread.c:464
ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:153
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
other info that might help us debug this:
Chain exists of:
&nilfs->ns_sem --> sb_internal#2 --> &nilfs->ns_segctor_sem
Possible unsafe locking scenario:
CPU0 CPU1
---- ----
lock(&nilfs->ns_segctor_sem);
lock(sb_internal#2);
lock(&nilfs->ns_segctor_sem);
lock(&nilfs->ns_sem);
*** DEADLOCK ***
1 lock held by segctord/5299:
#0: ffff88801189e2a0 (&nilfs->ns_segctor_sem){++++}-{4:4}, at: nilfs_transaction_lock+0x253/0x4c0 fs/nilfs2/segment.c:357
stack backtrace:
CPU: 0 UID: 0 PID: 5299 Comm: segctord Not tainted 6.15.0-rc4-syzkaller-00296-ge8ab83e34bdc #0 PREEMPT(full)
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
Call Trace:
<TASK>
dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
print_circular_bug+0x2ee/0x310 kernel/locking/lockdep.c:2079
check_noncircular+0x134/0x160 kernel/locking/lockdep.c:2211
check_prev_add kernel/locking/lockdep.c:3166 [inline]
check_prevs_add kernel/locking/lockdep.c:3285 [inline]
validate_chain+0xb9b/0x2140 kernel/locking/lockdep.c:3909
__lock_acquire+0xaac/0xd20 kernel/locking/lockdep.c:5235
lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5866
down_write+0x96/0x1f0 kernel/locking/rwsem.c:1577
nilfs_segctor_construct+0x2b1/0x690 fs/nilfs2/segment.c:2485
nilfs_segctor_thread_construct fs/nilfs2/segment.c:2586 [inline]
nilfs_segctor_thread+0x6f7/0xe00 fs/nilfs2/segment.c:2700
kthread+0x70e/0x8a0 kernel/kthread.c:464
ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:153
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
</TASK>
---
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