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Message-ID: <68681431.a00a0220.c7b3.0021.GAE@google.com>
Date: Fri, 04 Jul 2025 10:49:37 -0700
From: syzbot <syzbot+9200a5f34919fd7fd788@...kaller.appspotmail.com>
To: adilger.kernel@...ger.ca, linux-ext4@...r.kernel.org,
linux-kernel@...r.kernel.org, syzkaller-bugs@...glegroups.com, tytso@....edu
Subject: [syzbot] [ext4?] possible deadlock in ext4_page_mkwrite
Hello,
syzbot found the following issue on:
HEAD commit: d0b3b7b22dfa Linux 6.16-rc4
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=12d41982580000
kernel config: https://syzkaller.appspot.com/x/.config?x=e29b8115bf337f53
dashboard link: https://syzkaller.appspot.com/bug?extid=9200a5f34919fd7fd788
compiler: Debian clang version 20.1.6 (++20250514063057+1e4d39e07757-1~exp1~20250514183223.118), Debian LLD 20.1.6
Unfortunately, I don't have any reproducer for this issue yet.
Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/afd8a00e0f2e/disk-d0b3b7b2.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/a71883723588/vmlinux-d0b3b7b2.xz
kernel image: https://storage.googleapis.com/syzbot-assets/5dd703d981fd/bzImage-d0b3b7b2.xz
IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+9200a5f34919fd7fd788@...kaller.appspotmail.com
loop9: detected capacity change from 0 to 2048
EXT4-fs (loop9): mounted filesystem 00000000-0000-0000-0000-000000000000 r/w without journal. Quota mode: none.
======================================================
WARNING: possible circular locking dependency detected
6.16.0-rc4-syzkaller #0 Not tainted
------------------------------------------------------
syz.9.925/12720 is trying to acquire lock:
ffff888045180520 (sb_pagefaults){++++}-{0:0}, at: percpu_down_read_freezable include/linux/percpu-rwsem.h:83 [inline]
ffff888045180520 (sb_pagefaults){++++}-{0:0}, at: __sb_start_write include/linux/fs.h:1795 [inline]
ffff888045180520 (sb_pagefaults){++++}-{0:0}, at: sb_start_pagefault include/linux/fs.h:1960 [inline]
ffff888045180520 (sb_pagefaults){++++}-{0:0}, at: ext4_page_mkwrite+0x1e3/0x1110 fs/ext4/inode.c:6576
but task is already holding lock:
ffff88807a2fcb60 (&mm->mmap_lock){++++}-{4:4}, at: mmap_read_trylock include/linux/mmap_lock.h:431 [inline]
ffff88807a2fcb60 (&mm->mmap_lock){++++}-{4:4}, at: get_mmap_lock_carefully mm/mmap_lock.c:188 [inline]
ffff88807a2fcb60 (&mm->mmap_lock){++++}-{4:4}, at: lock_mm_and_find_vma+0x32/0x300 mm/mmap_lock.c:248
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #4 (&mm->mmap_lock){++++}-{4:4}:
lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5871
__might_fault+0xcc/0x130 mm/memory.c:6971
_inline_copy_to_user include/linux/uaccess.h:192 [inline]
_copy_to_user+0x2c/0xb0 lib/usercopy.c:26
copy_to_user include/linux/uaccess.h:225 [inline]
fiemap_fill_next_extent+0x1c0/0x390 fs/ioctl.c:145
ocfs2_fiemap+0x888/0xc90 fs/ocfs2/extent_map.c:806
ioctl_fiemap fs/ioctl.c:220 [inline]
do_vfs_ioctl+0x16d3/0x1990 fs/ioctl.c:841
__do_sys_ioctl fs/ioctl.c:905 [inline]
__se_sys_ioctl+0x82/0x170 fs/ioctl.c:893
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
-> #3 (&ocfs2_quota_ip_alloc_sem_key){++++}-{4:4}:
lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5871
down_write+0x96/0x1f0 kernel/locking/rwsem.c:1577
ocfs2_create_local_dquot+0x19d/0x1a40 fs/ocfs2/quota_local.c:1227
ocfs2_acquire_dquot+0x80f/0xb30 fs/ocfs2/quota_global.c:883
dqget+0x7b1/0xf10 fs/quota/dquot.c:977
__dquot_initialize+0x3b3/0xcb0 fs/quota/dquot.c:1505
ocfs2_get_init_inode+0x13b/0x1b0 fs/ocfs2/namei.c:202
ocfs2_mknod+0x863/0x2050 fs/ocfs2/namei.c:310
ocfs2_create+0x1a5/0x440 fs/ocfs2/namei.c:673
lookup_open fs/namei.c:3717 [inline]
open_last_lookups fs/namei.c:3816 [inline]
path_openat+0x14f4/0x3830 fs/namei.c:4052
do_filp_open+0x1fa/0x410 fs/namei.c:4082
do_sys_openat2+0x121/0x1c0 fs/open.c:1437
do_sys_open fs/open.c:1452 [inline]
__do_sys_openat fs/open.c:1468 [inline]
__se_sys_openat fs/open.c:1463 [inline]
__x64_sys_openat+0x138/0x170 fs/open.c:1463
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
-> #2 (&dquot->dq_lock){+.+.}-{4:4}:
lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5871
__mutex_lock_common kernel/locking/mutex.c:602 [inline]
__mutex_lock+0x182/0xe80 kernel/locking/mutex.c:747
dquot_release+0x66/0x600 fs/quota/dquot.c:531
ext4_release_dquot+0x3ee/0x6c0 fs/ext4/ext4_jbd2.h:-1
quota_release_workfn+0x35f/0x610 fs/quota/dquot.c:840
process_one_work kernel/workqueue.c:3238 [inline]
process_scheduled_works+0xae1/0x17b0 kernel/workqueue.c:3321
worker_thread+0x8a0/0xda0 kernel/workqueue.c:3402
kthread+0x711/0x8a0 kernel/kthread.c:464
ret_from_fork+0x3fc/0x770 arch/x86/kernel/process.c:148
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
-> #1 (sb_internal){++++}-{0:0}:
lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5871
percpu_down_write+0x54/0x330 kernel/locking/percpu-rwsem.c:232
sb_wait_write fs/super.c:1900 [inline]
freeze_super+0x8b7/0x1130 fs/super.c:2183
fs_bdev_freeze+0x1a3/0x310 fs/super.c:1529
bdev_freeze+0xd8/0x220 block/bdev.c:298
ext4_force_shutdown+0x322/0x560 fs/ext4/ioctl.c:822
ext4_ioctl_shutdown fs/ext4/ioctl.c:857 [inline]
__ext4_ioctl fs/ext4/ioctl.c:1587 [inline]
ext4_ioctl+0x1d39/0x3510 fs/ext4/ioctl.c:1626
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:907 [inline]
__se_sys_ioctl+0xfc/0x170 fs/ioctl.c:893
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
-> #0 (sb_pagefaults){++++}-{0:0}:
check_prev_add kernel/locking/lockdep.c:3168 [inline]
check_prevs_add kernel/locking/lockdep.c:3287 [inline]
validate_chain+0xb9b/0x2140 kernel/locking/lockdep.c:3911
__lock_acquire+0xab9/0xd20 kernel/locking/lockdep.c:5240
lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5871
percpu_down_read_internal+0x48/0x1c0 include/linux/percpu-rwsem.h:53
percpu_down_read_freezable include/linux/percpu-rwsem.h:83 [inline]
__sb_start_write include/linux/fs.h:1795 [inline]
sb_start_pagefault include/linux/fs.h:1960 [inline]
ext4_page_mkwrite+0x1e3/0x1110 fs/ext4/inode.c:6576
do_page_mkwrite+0x14a/0x310 mm/memory.c:3378
do_shared_fault mm/memory.c:5666 [inline]
do_fault mm/memory.c:5728 [inline]
do_pte_missing mm/memory.c:4251 [inline]
handle_pte_fault mm/memory.c:6069 [inline]
__handle_mm_fault+0x1a60/0x5620 mm/memory.c:6212
handle_mm_fault+0x2d5/0x7f0 mm/memory.c:6381
do_user_addr_fault+0x764/0x1390 arch/x86/mm/fault.c:1387
handle_page_fault arch/x86/mm/fault.c:1476 [inline]
exc_page_fault+0x76/0xf0 arch/x86/mm/fault.c:1532
asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:623
rep_movs_alternative+0x4a/0x90 arch/x86/lib/copy_user_64.S:68
copy_user_generic arch/x86/include/asm/uaccess_64.h:126 [inline]
raw_copy_to_user arch/x86/include/asm/uaccess_64.h:147 [inline]
copy_to_user_iter lib/iov_iter.c:25 [inline]
iterate_ubuf include/linux/iov_iter.h:30 [inline]
iterate_and_advance2 include/linux/iov_iter.h:300 [inline]
iterate_and_advance include/linux/iov_iter.h:328 [inline]
_copy_to_iter+0x24c/0x16f0 lib/iov_iter.c:185
copy_to_iter include/linux/uio.h:220 [inline]
seq_read_iter+0xbeb/0xe10 fs/seq_file.c:281
new_sync_read fs/read_write.c:491 [inline]
vfs_read+0x4cd/0x980 fs/read_write.c:572
ksys_read+0x145/0x250 fs/read_write.c:715
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
other info that might help us debug this:
Chain exists of:
sb_pagefaults --> &ocfs2_quota_ip_alloc_sem_key --> &mm->mmap_lock
Possible unsafe locking scenario:
CPU0 CPU1
---- ----
rlock(&mm->mmap_lock);
lock(&ocfs2_quota_ip_alloc_sem_key);
lock(&mm->mmap_lock);
rlock(sb_pagefaults);
*** DEADLOCK ***
3 locks held by syz.9.925/12720:
#0: ffff8880318307f8 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x247/0x320 fs/file.c:1217
#1: ffff8880383a29e0 (&p->lock){+.+.}-{4:4}, at: seq_read_iter+0xb7/0xe10 fs/seq_file.c:182
#2: ffff88807a2fcb60 (&mm->mmap_lock){++++}-{4:4}, at: mmap_read_trylock include/linux/mmap_lock.h:431 [inline]
#2: ffff88807a2fcb60 (&mm->mmap_lock){++++}-{4:4}, at: get_mmap_lock_carefully mm/mmap_lock.c:188 [inline]
#2: ffff88807a2fcb60 (&mm->mmap_lock){++++}-{4:4}, at: lock_mm_and_find_vma+0x32/0x300 mm/mmap_lock.c:248
stack backtrace:
CPU: 1 UID: 0 PID: 12720 Comm: syz.9.925 Not tainted 6.16.0-rc4-syzkaller #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
Call Trace:
<TASK>
dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
print_circular_bug+0x2ee/0x310 kernel/locking/lockdep.c:2046
check_noncircular+0x134/0x160 kernel/locking/lockdep.c:2178
check_prev_add kernel/locking/lockdep.c:3168 [inline]
check_prevs_add kernel/locking/lockdep.c:3287 [inline]
validate_chain+0xb9b/0x2140 kernel/locking/lockdep.c:3911
__lock_acquire+0xab9/0xd20 kernel/locking/lockdep.c:5240
lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5871
percpu_down_read_internal+0x48/0x1c0 include/linux/percpu-rwsem.h:53
percpu_down_read_freezable include/linux/percpu-rwsem.h:83 [inline]
__sb_start_write include/linux/fs.h:1795 [inline]
sb_start_pagefault include/linux/fs.h:1960 [inline]
ext4_page_mkwrite+0x1e3/0x1110 fs/ext4/inode.c:6576
do_page_mkwrite+0x14a/0x310 mm/memory.c:3378
do_shared_fault mm/memory.c:5666 [inline]
do_fault mm/memory.c:5728 [inline]
do_pte_missing mm/memory.c:4251 [inline]
handle_pte_fault mm/memory.c:6069 [inline]
__handle_mm_fault+0x1a60/0x5620 mm/memory.c:6212
handle_mm_fault+0x2d5/0x7f0 mm/memory.c:6381
do_user_addr_fault+0x764/0x1390 arch/x86/mm/fault.c:1387
handle_page_fault arch/x86/mm/fault.c:1476 [inline]
exc_page_fault+0x76/0xf0 arch/x86/mm/fault.c:1532
asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:623
RIP: 0010:rep_movs_alternative+0x4a/0x90 arch/x86/lib/copy_user_64.S:74
Code: 00 04 00 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 00 48 8b 06 48 89 07 48 83 c6 08 48 83 c7 08 83 e9 08 74 db 83 f9 08 73 e8 eb c5 <f3> a4 e9 0f 00 04 00 48 8b 06 48 89 07 48 8d 47 08 48 83 e0 f8 48
RSP: 0018:ffffc90003c8fa58 EFLAGS: 00050202
RAX: ffffffff84b83201 RBX: ffff88807c14c000 RCX: 00000000000004a1
RDX: 0000000000000000 RSI: ffff88807c14c000 RDI: 00002000000061c0
RBP: ffffc90003c8fbb0 R08: ffff88807c14c4a0 R09: 1ffff1100f829894
R10: dffffc0000000000 R11: ffffed100f829895 R12: 1ffff92000791faf
R13: 00002000000061c0 R14: ffffc90003c8fd88 R15: 00000000000004a1
copy_user_generic arch/x86/include/asm/uaccess_64.h:126 [inline]
raw_copy_to_user arch/x86/include/asm/uaccess_64.h:147 [inline]
copy_to_user_iter lib/iov_iter.c:25 [inline]
iterate_ubuf include/linux/iov_iter.h:30 [inline]
iterate_and_advance2 include/linux/iov_iter.h:300 [inline]
iterate_and_advance include/linux/iov_iter.h:328 [inline]
_copy_to_iter+0x24c/0x16f0 lib/iov_iter.c:185
copy_to_iter include/linux/uio.h:220 [inline]
seq_read_iter+0xbeb/0xe10 fs/seq_file.c:281
new_sync_read fs/read_write.c:491 [inline]
vfs_read+0x4cd/0x980 fs/read_write.c:572
ksys_read+0x145/0x250 fs/read_write.c:715
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f3bba18e929
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f3bbb0c4038 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
RAX: ffffffffffffffda RBX: 00007f3bba3b5fa0 RCX: 00007f3bba18e929
RDX: 0000000000002020 RSI: 00002000000061c0 RDI: 0000000000000005
RBP: 00007f3bba210b39 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f3bba3b5fa0 R15: 00007ffe94043458
</TASK>
----------------
Code disassembly (best guess):
0: 00 04 00 add %al,(%rax,%rax,1)
3: 66 2e 0f 1f 84 00 00 cs nopw 0x0(%rax,%rax,1)
a: 00 00 00
d: 0f 1f 00 nopl (%rax)
10: 48 8b 06 mov (%rsi),%rax
13: 48 89 07 mov %rax,(%rdi)
16: 48 83 c6 08 add $0x8,%rsi
1a: 48 83 c7 08 add $0x8,%rdi
1e: 83 e9 08 sub $0x8,%ecx
21: 74 db je 0xfffffffe
23: 83 f9 08 cmp $0x8,%ecx
26: 73 e8 jae 0x10
28: eb c5 jmp 0xffffffef
* 2a: f3 a4 rep movsb %ds:(%rsi),%es:(%rdi) <-- trapping instruction
2c: e9 0f 00 04 00 jmp 0x40040
31: 48 8b 06 mov (%rsi),%rax
34: 48 89 07 mov %rax,(%rdi)
37: 48 8d 47 08 lea 0x8(%rdi),%rax
3b: 48 83 e0 f8 and $0xfffffffffffffff8,%rax
3f: 48 rex.W
---
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 syzkaller@...glegroups.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 to overwrite report's subsystems, reply with:
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(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
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