[syzbot] [nilfs?] possible deadlock in __nilfs_error (3)
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syzbot
Apr 29, 2025, 10:26:28 PM4/29/25
to konishi...@gmail.com, linux-...@vger.kernel.org, linux...@vger.kernel.org, syzkall...@googlegroups.com
Hello,
syzbot found the following issue on:
HEAD commit: ca91b9500108 Merge tag 'v6.15-rc4-ksmbd-server-fixes' of g..
git tree: upstream
console+strace: https://syzkaller.appspot.com/x/log.txt?x=172188d4580000
kernel config: https://syzkaller.appspot.com/x/.config?x=a42a9d552788177b
dashboard link: https://syzkaller.appspot.com/bug?extid=00f7f5b884b117ee6773
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=14a00a70580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=114b8774580000
Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/8f91302b28da/disk-ca91b950.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/99926b0845ed/vmlinux-ca91b950.xz
kernel image: https://storage.googleapis.com/syzbot-assets/ace62028a7c9/bzImage-ca91b950.xz
mounted in repro #1: https://storage.googleapis.com/syzbot-assets/5c8198c5e35a/mount_0.gz
mounted in repro #2: https://storage.googleapis.com/syzbot-assets/a89d3d8742e8/mount_3.gz
fsck result: failed (log: https://syzkaller.appspot.com/x/fsck.log?x=12dabb74580000)
IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+00f7f5...@syzkaller.appspotmail.com
NILFS (loop0): vblocknr = 23 has abnormal lifetime: start cno (= 4294967298) > current cno (= 3)
NILFS error (device loop0): nilfs_bmap_propagate: broken bmap (inode number=4)
======================================================
WARNING: possible circular locking dependency detected
6.15.0-rc4-syzkaller-00021-gca91b9500108 #0 Not tainted
------------------------------------------------------
segctord/5821 is trying to acquire lock:
ffff88814d79f090 (&nilfs->ns_sem){++++}-{4:4}, at: nilfs_set_error fs/nilfs2/super.c:92 [inline]
ffff88814d79f090 (&nilfs->ns_sem){++++}-{4:4}, at: __nilfs_error+0x1ca/0x4b0 fs/nilfs2/super.c:141
but task is already holding lock:
ffff88814d79f2a0 (&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:
-> #6 (&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_page_mkwrite+0x8b0/0xc20 fs/nilfs2/file.c:95
do_page_mkwrite+0x14a/0x310 mm/memory.c:3287
wp_page_shared mm/memory.c:3688 [inline]
do_wp_page+0x2626/0x5760 mm/memory.c:3907
handle_pte_fault mm/memory.c:6013 [inline]
__handle_mm_fault+0x1028/0x5380 mm/memory.c:6140
handle_mm_fault+0x2d5/0x7f0 mm/memory.c:6309
do_user_addr_fault+0xa81/0x1390 arch/x86/mm/fault.c:1337
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
-> #5 (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
wp_page_shared mm/memory.c:3688 [inline]
do_wp_page+0x2626/0x5760 mm/memory.c:3907
handle_pte_fault mm/memory.c:6013 [inline]
__handle_mm_fault+0x1028/0x5380 mm/memory.c:6140
handle_mm_fault+0x2d5/0x7f0 mm/memory.c:6309
do_user_addr_fault+0xa81/0x1390 arch/x86/mm/fault.c:1337
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
-> #4 (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
wp_page_shared mm/memory.c:3688 [inline]
do_wp_page+0x2626/0x5760 mm/memory.c:3907
handle_pte_fault mm/memory.c:6013 [inline]
__handle_mm_fault+0x1028/0x5380 mm/memory.c:6140
handle_mm_fault+0x2d5/0x7f0 mm/memory.c:6309
do_user_addr_fault+0xa81/0x1390 arch/x86/mm/fault.c:1337
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 (vm_lock){++++}-{0:0}:
lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5866
__vma_enter_locked+0x182/0x380 mm/memory.c:6473
__vma_start_write+0x1e/0x120 mm/memory.c:6497
vma_start_write include/linux/mm.h:829 [inline]
mprotect_fixup+0x571/0x9b0 mm/mprotect.c:670
setup_arg_pages+0x53a/0xaa0 fs/exec.c:780
load_elf_binary+0xb7a/0x27b0 fs/binfmt_elf.c:1019
search_binary_handler fs/exec.c:1778 [inline]
exec_binprm fs/exec.c:1810 [inline]
bprm_execve+0x999/0x1440 fs/exec.c:1862
kernel_execve+0x8f0/0x9f0 fs/exec.c:2028
try_to_run_init_process+0x13/0x60 init/main.c:1385
kernel_init+0xad/0x1d0 init/main.c:1513
ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:153
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
-> #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#7){++++}-{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_set_error fs/nilfs2/super.c:92 [inline]
__nilfs_error+0x1ca/0x4b0 fs/nilfs2/super.c:141
nilfs_bmap_convert_error fs/nilfs2/bmap.c:35 [inline]
nilfs_bmap_propagate+0x108/0x130 fs/nilfs2/bmap.c:332
nilfs_collect_file_data+0x4f/0xd0 fs/nilfs2/segment.c:589
nilfs_segctor_apply_buffers+0x161/0x330 fs/nilfs2/segment.c:1010
nilfs_segctor_scan_file+0x68e/0x8e0 fs/nilfs2/segment.c:1059
nilfs_segctor_collect_blocks fs/nilfs2/segment.c:1254 [inline]
nilfs_segctor_collect fs/nilfs2/segment.c:1547 [inline]
nilfs_segctor_do_construct+0x1d46/0x6970 fs/nilfs2/segment.c:2122
nilfs_segctor_construct+0x17b/0x690 fs/nilfs2/segment.c:2478
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/5821:
#0: ffff88814d79f2a0 (&nilfs->ns_segctor_sem){++++}-{4:4}, at: nilfs_transaction_lock+0x253/0x4c0 fs/nilfs2/segment.c:357
stack backtrace:
CPU: 0 UID: 0 PID: 5821 Comm: segctord Not tainted 6.15.0-rc4-syzkaller-00021-gca91b9500108 #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/19/2025
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_set_error fs/nilfs2/super.c:92 [inline]
__nilfs_error+0x1ca/0x4b0 fs/nilfs2/super.c:141
nilfs_bmap_convert_error fs/nilfs2/bmap.c:35 [inline]
nilfs_bmap_propagate+0x108/0x130 fs/nilfs2/bmap.c:332
nilfs_collect_file_data+0x4f/0xd0 fs/nilfs2/segment.c:589
nilfs_segctor_apply_buffers+0x161/0x330 fs/nilfs2/segment.c:1010
nilfs_segctor_scan_file+0x68e/0x8e0 fs/nilfs2/segment.c:1059
nilfs_segctor_collect_blocks fs/nilfs2/segment.c:1254 [inline]
nilfs_segctor_collect fs/nilfs2/segment.c:1547 [inline]
nilfs_segctor_do_construct+0x1d46/0x6970 fs/nilfs2/segment.c:2122
nilfs_segctor_construct+0x17b/0x690 fs/nilfs2/segment.c:2478
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>
Remounting filesystem read-only
---
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syzbot found the following issue on:
HEAD commit: ca91b9500108 Merge tag 'v6.15-rc4-ksmbd-server-fixes' of g..
git tree: upstream
console+strace: https://syzkaller.appspot.com/x/log.txt?x=172188d4580000
kernel config: https://syzkaller.appspot.com/x/.config?x=a42a9d552788177b
dashboard link: https://syzkaller.appspot.com/bug?extid=00f7f5b884b117ee6773
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=14a00a70580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=114b8774580000
Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/8f91302b28da/disk-ca91b950.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/99926b0845ed/vmlinux-ca91b950.xz
kernel image: https://storage.googleapis.com/syzbot-assets/ace62028a7c9/bzImage-ca91b950.xz
mounted in repro #1: https://storage.googleapis.com/syzbot-assets/5c8198c5e35a/mount_0.gz
mounted in repro #2: https://storage.googleapis.com/syzbot-assets/a89d3d8742e8/mount_3.gz
fsck result: failed (log: https://syzkaller.appspot.com/x/fsck.log?x=12dabb74580000)
IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+00f7f5...@syzkaller.appspotmail.com
NILFS (loop0): vblocknr = 23 has abnormal lifetime: start cno (= 4294967298) > current cno (= 3)
NILFS error (device loop0): nilfs_bmap_propagate: broken bmap (inode number=4)
======================================================
WARNING: possible circular locking dependency detected
6.15.0-rc4-syzkaller-00021-gca91b9500108 #0 Not tainted
------------------------------------------------------
segctord/5821 is trying to acquire lock:
ffff88814d79f090 (&nilfs->ns_sem){++++}-{4:4}, at: nilfs_set_error fs/nilfs2/super.c:92 [inline]
ffff88814d79f090 (&nilfs->ns_sem){++++}-{4:4}, at: __nilfs_error+0x1ca/0x4b0 fs/nilfs2/super.c:141
but task is already holding lock:
ffff88814d79f2a0 (&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:
-> #6 (&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_page_mkwrite+0x8b0/0xc20 fs/nilfs2/file.c:95
do_page_mkwrite+0x14a/0x310 mm/memory.c:3287
wp_page_shared mm/memory.c:3688 [inline]
do_wp_page+0x2626/0x5760 mm/memory.c:3907
handle_pte_fault mm/memory.c:6013 [inline]
__handle_mm_fault+0x1028/0x5380 mm/memory.c:6140
handle_mm_fault+0x2d5/0x7f0 mm/memory.c:6309
do_user_addr_fault+0xa81/0x1390 arch/x86/mm/fault.c:1337
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
-> #5 (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
wp_page_shared mm/memory.c:3688 [inline]
do_wp_page+0x2626/0x5760 mm/memory.c:3907
handle_pte_fault mm/memory.c:6013 [inline]
__handle_mm_fault+0x1028/0x5380 mm/memory.c:6140
handle_mm_fault+0x2d5/0x7f0 mm/memory.c:6309
do_user_addr_fault+0xa81/0x1390 arch/x86/mm/fault.c:1337
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
-> #4 (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
wp_page_shared mm/memory.c:3688 [inline]
do_wp_page+0x2626/0x5760 mm/memory.c:3907
handle_pte_fault mm/memory.c:6013 [inline]
__handle_mm_fault+0x1028/0x5380 mm/memory.c:6140
handle_mm_fault+0x2d5/0x7f0 mm/memory.c:6309
do_user_addr_fault+0xa81/0x1390 arch/x86/mm/fault.c:1337
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 (vm_lock){++++}-{0:0}:
lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5866
__vma_enter_locked+0x182/0x380 mm/memory.c:6473
__vma_start_write+0x1e/0x120 mm/memory.c:6497
vma_start_write include/linux/mm.h:829 [inline]
mprotect_fixup+0x571/0x9b0 mm/mprotect.c:670
setup_arg_pages+0x53a/0xaa0 fs/exec.c:780
load_elf_binary+0xb7a/0x27b0 fs/binfmt_elf.c:1019
search_binary_handler fs/exec.c:1778 [inline]
exec_binprm fs/exec.c:1810 [inline]
bprm_execve+0x999/0x1440 fs/exec.c:1862
kernel_execve+0x8f0/0x9f0 fs/exec.c:2028
try_to_run_init_process+0x13/0x60 init/main.c:1385
kernel_init+0xad/0x1d0 init/main.c:1513
ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:153
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
-> #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#7){++++}-{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_set_error fs/nilfs2/super.c:92 [inline]
__nilfs_error+0x1ca/0x4b0 fs/nilfs2/super.c:141
nilfs_bmap_convert_error fs/nilfs2/bmap.c:35 [inline]
nilfs_bmap_propagate+0x108/0x130 fs/nilfs2/bmap.c:332
nilfs_collect_file_data+0x4f/0xd0 fs/nilfs2/segment.c:589
nilfs_segctor_apply_buffers+0x161/0x330 fs/nilfs2/segment.c:1010
nilfs_segctor_scan_file+0x68e/0x8e0 fs/nilfs2/segment.c:1059
nilfs_segctor_collect_blocks fs/nilfs2/segment.c:1254 [inline]
nilfs_segctor_collect fs/nilfs2/segment.c:1547 [inline]
nilfs_segctor_do_construct+0x1d46/0x6970 fs/nilfs2/segment.c:2122
nilfs_segctor_construct+0x17b/0x690 fs/nilfs2/segment.c:2478
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/5821:
#0: ffff88814d79f2a0 (&nilfs->ns_segctor_sem){++++}-{4:4}, at: nilfs_transaction_lock+0x253/0x4c0 fs/nilfs2/segment.c:357
stack backtrace:
CPU: 0 UID: 0 PID: 5821 Comm: segctord Not tainted 6.15.0-rc4-syzkaller-00021-gca91b9500108 #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/19/2025
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_set_error fs/nilfs2/super.c:92 [inline]
__nilfs_error+0x1ca/0x4b0 fs/nilfs2/super.c:141
nilfs_bmap_convert_error fs/nilfs2/bmap.c:35 [inline]
nilfs_bmap_propagate+0x108/0x130 fs/nilfs2/bmap.c:332
nilfs_collect_file_data+0x4f/0xd0 fs/nilfs2/segment.c:589
nilfs_segctor_apply_buffers+0x161/0x330 fs/nilfs2/segment.c:1010
nilfs_segctor_scan_file+0x68e/0x8e0 fs/nilfs2/segment.c:1059
nilfs_segctor_collect_blocks fs/nilfs2/segment.c:1254 [inline]
nilfs_segctor_collect fs/nilfs2/segment.c:1547 [inline]
nilfs_segctor_do_construct+0x1d46/0x6970 fs/nilfs2/segment.c:2122
nilfs_segctor_construct+0x17b/0x690 fs/nilfs2/segment.c:2478
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>
Remounting filesystem read-only
---
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 syzk...@googlegroups.com.
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 syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
If you attach or paste a git patch, syzbot will apply it before testing.
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
Ryusuke Konishi
Apr 30, 2025, 12:37:44 PM4/30/25
to syzbot+00f7f5...@syzkaller.appspotmail.com, linux-...@vger.kernel.org, syzkall...@googlegroups.com
Try removing unnecessary ns_sem lock in init_nilfs() to eliminate lock
dependencies that were causing false positive deadlock warnings in
__nilfs_error() etc.
#syz test
diff --git a/fs/nilfs2/the_nilfs.c b/fs/nilfs2/the_nilfs.c
index cb01ea81724d..d0bcf744c553 100644
--- a/fs/nilfs2/the_nilfs.c
+++ b/fs/nilfs2/the_nilfs.c
@@ -705,8 +705,6 @@ int init_nilfs(struct the_nilfs *nilfs, struct super_block *sb)
int blocksize;
int err;
- down_write(&nilfs->ns_sem);
-
blocksize = sb_min_blocksize(sb, NILFS_MIN_BLOCK_SIZE);
if (!blocksize) {
nilfs_err(sb, "unable to set blocksize");
@@ -779,7 +777,6 @@ int init_nilfs(struct the_nilfs *nilfs, struct super_block *sb)
set_nilfs_init(nilfs);
err = 0;
out:
- up_write(&nilfs->ns_sem);
return err;
failed_sbh:
--
2.43.0
dependencies that were causing false positive deadlock warnings in
__nilfs_error() etc.
#syz test
diff --git a/fs/nilfs2/the_nilfs.c b/fs/nilfs2/the_nilfs.c
index cb01ea81724d..d0bcf744c553 100644
--- a/fs/nilfs2/the_nilfs.c
+++ b/fs/nilfs2/the_nilfs.c
@@ -705,8 +705,6 @@ int init_nilfs(struct the_nilfs *nilfs, struct super_block *sb)
int blocksize;
int err;
- down_write(&nilfs->ns_sem);
-
blocksize = sb_min_blocksize(sb, NILFS_MIN_BLOCK_SIZE);
if (!blocksize) {
nilfs_err(sb, "unable to set blocksize");
@@ -779,7 +777,6 @@ int init_nilfs(struct the_nilfs *nilfs, struct super_block *sb)
set_nilfs_init(nilfs);
err = 0;
out:
- up_write(&nilfs->ns_sem);
return err;
failed_sbh:
--
2.43.0
syzbot
Apr 30, 2025, 6:16:05 PM4/30/25
to konishi...@gmail.com, linux-...@vger.kernel.org, syzkall...@googlegroups.com
Hello,
syzbot has tested the proposed patch and the reproducer did not trigger any issue:
Reported-by: syzbot+00f7f5...@syzkaller.appspotmail.com
Tested-by: syzbot+00f7f5...@syzkaller.appspotmail.com
Tested on:
commit: 7a13c14e Merge tag 'for-6.15-rc4-tag' of git://git.ker..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=169daf74580000
Note: testing is done by a robot and is best-effort only.
syzbot has tested the proposed patch and the reproducer did not trigger any issue:
Reported-by: syzbot+00f7f5...@syzkaller.appspotmail.com
Tested-by: syzbot+00f7f5...@syzkaller.appspotmail.com
Tested on:
commit: 7a13c14e Merge tag 'for-6.15-rc4-tag' of git://git.ker..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=169daf74580000
kernel config: https://syzkaller.appspot.com/x/.config?x=a42a9d552788177b
dashboard link: https://syzkaller.appspot.com/bug?extid=00f7f5b884b117ee6773
compiler: Debian clang version 20.1.2 (++20250402124445+58df0ef89dd6-1~exp1~20250402004600.97), Debian LLD 20.1.2
patch: https://syzkaller.appspot.com/x/patch.diff?x=10e731b3980000
dashboard link: https://syzkaller.appspot.com/bug?extid=00f7f5b884b117ee6773
compiler: Debian clang version 20.1.2 (++20250402124445+58df0ef89dd6-1~exp1~20250402004600.97), Debian LLD 20.1.2
Note: testing is done by a robot and is best-effort only.
Ryusuke Konishi
May 3, 2025, 1:33:34 AM5/3/25
to Andrew Morton, linux...@vger.kernel.org, syzbot+00f7f5...@syzkaller.appspotmail.com, syzbot+f30591...@syzkaller.appspotmail.com, syzkall...@googlegroups.com, linux-...@vger.kernel.org
After commit c0e473a0d226 ("block: fix race between set_blocksize and
read paths") was merged, set_blocksize() called by sb_set_blocksize()
now locks the inode of the backing device file. As a result of this
change, syzbot started reporting deadlock warnings due to a circular
dependency involving the semaphore "ns_sem" of the nilfs object, the
inode lock of the backing device file, and the locks that this inode
lock is transitively dependent on.
This is caused by a new lock dependency added by the above change,
since init_nilfs() calls sb_set_blocksize() in the lock section of
"ns_sem". However, these warnings are false positives because
init_nilfs() is called in the early stage of the mount operation and
the filesystem has not yet started.
The reason why "ns_sem" is locked in init_nilfs() was to avoid a race
condition in nilfs_fill_super() caused by sharing a nilfs object among
multiple filesystem instances (super block structures) in the early
implementation. However, nilfs objects and super block structures
have long ago become one-to-one, and there is no longer any need to
use the semaphore there.
So, fix this issue by removing the use of the semaphore "ns_sem" in
init_nilfs().
Signed-off-by: Ryusuke Konishi <konishi...@gmail.com>
Reported-by: syzbot+00f7f5...@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=00f7f5b884b117ee6773
Tested-by: syzbot+00f7f5...@syzkaller.appspotmail.com
Reported-by: syzbot+f30591...@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=f30591e72bfc24d4715b
Tested-by: syzbot+f30591...@syzkaller.appspotmail.com
Fixes: c0e473a0d226 ("block: fix race between set_blocksize and read paths")
---
Hi Andrew, please apply this as a regression fix.
This resolves some deadlock warnings reported by syzbot since a change
in 6.15-rc4.
Thanks,
Ryusuke Konishi
fs/nilfs2/the_nilfs.c | 3 ---
1 file changed, 3 deletions(-)
read paths") was merged, set_blocksize() called by sb_set_blocksize()
now locks the inode of the backing device file. As a result of this
change, syzbot started reporting deadlock warnings due to a circular
dependency involving the semaphore "ns_sem" of the nilfs object, the
inode lock of the backing device file, and the locks that this inode
lock is transitively dependent on.
This is caused by a new lock dependency added by the above change,
since init_nilfs() calls sb_set_blocksize() in the lock section of
"ns_sem". However, these warnings are false positives because
init_nilfs() is called in the early stage of the mount operation and
the filesystem has not yet started.
The reason why "ns_sem" is locked in init_nilfs() was to avoid a race
condition in nilfs_fill_super() caused by sharing a nilfs object among
multiple filesystem instances (super block structures) in the early
implementation. However, nilfs objects and super block structures
have long ago become one-to-one, and there is no longer any need to
use the semaphore there.
So, fix this issue by removing the use of the semaphore "ns_sem" in
init_nilfs().
Signed-off-by: Ryusuke Konishi <konishi...@gmail.com>
Reported-by: syzbot+00f7f5...@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=00f7f5b884b117ee6773
Tested-by: syzbot+00f7f5...@syzkaller.appspotmail.com
Reported-by: syzbot+f30591...@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=f30591e72bfc24d4715b
Tested-by: syzbot+f30591...@syzkaller.appspotmail.com
Fixes: c0e473a0d226 ("block: fix race between set_blocksize and read paths")
---
Hi Andrew, please apply this as a regression fix.
This resolves some deadlock warnings reported by syzbot since a change
in 6.15-rc4.
Thanks,
Ryusuke Konishi
fs/nilfs2/the_nilfs.c | 3 ---
1 file changed, 3 deletions(-)
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