syzbot


INFO: task hung in ntfs_fallocate

Status: upstream: reported C repro on 2026/01/13 10:08
Bug presence: origin:lts-only
[Documentation on labels]
Reported-by: syzbot+03096c353c6b825ff816@syzkaller.appspotmail.com
First crash: 4d03h, last: 2d06h
Bug presence (2)
Date Name Commit Repro Result
2026/01/14 linux-5.15.y (ToT) 68efe5a6c16a C [report] INFO: task hung in ntfs_fallocate
2026/01/14 upstream (ToT) b54345928fa1 C Didn't crash
Similar bugs (2)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream INFO: task hung in ntfs_fallocate ntfs3 1 C inconclusive 2 33d 43d 0/29 upstream: reported C repro on 2025/12/05 05:04
linux-6.1 INFO: task hung in ntfs_fallocate 1 1 898d 898d 0/3 auto-obsoleted due to no activity on 2023/11/11 09:02

Sample crash report:
INFO: task syz.0.17:4323 blocked for more than 143 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.0.17        state:D stack:29088 pid: 4323 ppid:  4303 flags:0x00004004
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5049 [inline]
 __schedule+0x11bb/0x4390 kernel/sched/core.c:6395
 schedule+0x11b/0x1e0 kernel/sched/core.c:6478
 rwsem_down_write_slowpath+0xc46/0x11f0 kernel/locking/rwsem.c:1165
 inode_lock include/linux/fs.h:787 [inline]
 ntfs_fallocate+0x1a9/0xcc0 fs/ntfs3/file.c:558
 vfs_fallocate+0x587/0x6f0 fs/open.c:308
 ksys_fallocate fs/open.c:331 [inline]
 __do_sys_fallocate fs/open.c:339 [inline]
 __se_sys_fallocate fs/open.c:337 [inline]
 __x64_sys_fallocate+0xbd/0x100 fs/open.c:337
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7f3d8b037749
RSP: 002b:00007f3d8a685038 EFLAGS: 00000246 ORIG_RAX: 000000000000011d
RAX: ffffffffffffffda RBX: 00007f3d8b28e090 RCX: 00007f3d8b037749
RDX: 000000000000000a RSI: 0000000000000001 RDI: 0000000000000005
RBP: 00007f3d8b0bbf91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000009 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f3d8b28e128 R14: 00007f3d8b28e090 R15: 00007fff657e1488
 </TASK>

Showing all locks held in the system:
3 locks held by kworker/u4:0/9:
1 lock held by khungtaskd/27:
 #0: ffffffff8c11c720 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x0/0x30
2 locks held by getty/3950:
 #0: ffff88814cbb7098 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x21/0x70 drivers/tty/tty_ldisc.c:252
 #1: ffffc90002cf62e8 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0x5ba/0x1a30 drivers/tty/n_tty.c:2158
4 locks held by syz.0.17/4322:
2 locks held by syz.0.17/4323:
 #0: ffff88801f176460 (sb_writers#13){.+.+}-{0:0}, at: file_start_write include/linux/fs.h:3043 [inline]
 #0: ffff88801f176460 (sb_writers#13){.+.+}-{0:0}, at: vfs_fallocate+0x4f4/0x6f0 fs/open.c:307
 #1: ffff88805f797240 (&sb->s_type->i_mutex_key#21){+.+.}-{3:3}, at: inode_lock include/linux/fs.h:787 [inline]
 #1: ffff88805f797240 (&sb->s_type->i_mutex_key#21){+.+.}-{3:3}, at: ntfs_fallocate+0x1a9/0xcc0 fs/ntfs3/file.c:558
4 locks held by syz.1.18/4351:
2 locks held by syz.1.18/4352:
 #0: ffff88801afe2460 (sb_writers#13){.+.+}-{0:0}, at: file_start_write include/linux/fs.h:3043 [inline]
 #0: ffff88801afe2460 (sb_writers#13){.+.+}-{0:0}, at: vfs_fallocate+0x4f4/0x6f0 fs/open.c:307
 #1: ffff88805f737240 (&sb->s_type->i_mutex_key#21){+.+.}-{3:3}, at: inode_lock include/linux/fs.h:787 [inline]
 #1: ffff88805f737240 (&sb->s_type->i_mutex_key#21){+.+.}-{3:3}, at: ntfs_fallocate+0x1a9/0xcc0 fs/ntfs3/file.c:558
3 locks held by syz.2.19/4378:
2 locks held by syz.2.19/4379:
 #0: ffff888024758460 (sb_writers#13){.+.+}-{0:0}, at: file_start_write include/linux/fs.h:3043 [inline]
 #0: ffff888024758460 (sb_writers#13){.+.+}-{0:0}, at: vfs_fallocate+0x4f4/0x6f0 fs/open.c:307
 #1: ffff88805f7d6ae0 (&sb->s_type->i_mutex_key#21){+.+.}-{3:3}, at: inode_lock include/linux/fs.h:787 [inline]
 #1: ffff88805f7d6ae0 (&sb->s_type->i_mutex_key#21){+.+.}-{3:3}, at: ntfs_fallocate+0x1a9/0xcc0 fs/ntfs3/file.c:558
4 locks held by syz.3.20/4400:
2 locks held by syz.3.20/4401:
 #0: ffff88807bcf2460 (sb_writers#13){.+.+}-{0:0}, at: file_start_write include/linux/fs.h:3043 [inline]
 #0: ffff88807bcf2460 (sb_writers#13){.+.+}-{0:0}, at: vfs_fallocate+0x4f4/0x6f0 fs/open.c:307
 #1: ffff88805f69eae0 (&sb->s_type->i_mutex_key#21){+.+.}-{3:3}, at: inode_lock include/linux/fs.h:787 [inline]
 #1: ffff88805f69eae0 (&sb->s_type->i_mutex_key#21){+.+.}-{3:3}, at: ntfs_fallocate+0x1a9/0xcc0 fs/ntfs3/file.c:558
4 locks held by syz.4.21/4431:
2 locks held by syz.4.21/4432:
 #0: ffff88807f05a460 (sb_writers#13){.+.+}-{0:0}, at: file_start_write include/linux/fs.h:3043 [inline]
 #0: ffff88807f05a460 (sb_writers#13){.+.+}-{0:0}, at: vfs_fallocate+0x4f4/0x6f0 fs/open.c:307
 #1: ffff888073f0a120 (&sb->s_type->i_mutex_key#21){+.+.}-{3:3}, at: inode_lock include/linux/fs.h:787 [inline]
 #1: ffff888073f0a120 (&sb->s_type->i_mutex_key#21){+.+.}-{3:3}, at: ntfs_fallocate+0x1a9/0xcc0 fs/ntfs3/file.c:558
4 locks held by syz.5.22/4466:
2 locks held by syz.5.22/4467:
 #0: ffff888075d08460 (sb_writers#13){.+.+}-{0:0}, at: file_start_write include/linux/fs.h:3043 [inline]
 #0: ffff888075d08460 (sb_writers#13){.+.+}-{0:0}, at: vfs_fallocate+0x4f4/0x6f0 fs/open.c:307
 #1: ffff888071b319c0 (&sb->s_type->i_mutex_key#21){+.+.}-{3:3}, at: inode_lock include/linux/fs.h:787 [inline]
 #1: ffff888071b319c0 (&sb->s_type->i_mutex_key#21){+.+.}-{3:3}, at: ntfs_fallocate+0x1a9/0xcc0 fs/ntfs3/file.c:558
4 locks held by syz.6.23/4497:
2 locks held by syz.6.23/4498:
 #0: ffff88805bad6460 (sb_writers#13){.+.+}-{0:0}, at: file_start_write include/linux/fs.h:3043 [inline]
 #0: ffff88805bad6460 (sb_writers#13){.+.+}-{0:0}, at: vfs_fallocate+0x4f4/0x6f0 fs/open.c:307
 #1: ffff88805f508b00 (&sb->s_type->i_mutex_key#21){+.+.}-{3:3}, at: inode_lock include/linux/fs.h:787 [inline]
 #1: ffff88805f508b00 (&sb->s_type->i_mutex_key#21){+.+.}-{3:3}, at: ntfs_fallocate+0x1a9/0xcc0 fs/ntfs3/file.c:558
4 locks held by syz.7.24/4532:
2 locks held by syz.7.24/4533:
 #0: ffff88805cf16460 (sb_writers#13){.+.+}-{0:0}, at: file_start_write include/linux/fs.h:3043 [inline]
 #0: ffff88805cf16460 (sb_writers#13){.+.+}-{0:0}, at: vfs_fallocate+0x4f4/0x6f0 fs/open.c:307
 #1: ffff888073f0cd60 (&sb->s_type->i_mutex_key#21){+.+.}-{3:3}, at: inode_lock include/linux/fs.h:787 [inline]
 #1: ffff888073f0cd60 (&sb->s_type->i_mutex_key#21){+.+.}-{3:3}, at: ntfs_fallocate+0x1a9/0xcc0 fs/ntfs3/file.c:558

=============================================

NMI backtrace for cpu 0
CPU: 0 PID: 27 Comm: khungtaskd Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0x168/0x230 lib/dump_stack.c:106
 nmi_cpu_backtrace+0x397/0x3d0 lib/nmi_backtrace.c:111
 nmi_trigger_cpumask_backtrace+0x163/0x280 lib/nmi_backtrace.c:62
 trigger_all_cpu_backtrace include/linux/nmi.h:148 [inline]
 check_hung_uninterruptible_tasks kernel/hung_task.c:212 [inline]
 watchdog+0xe0f/0xe50 kernel/hung_task.c:369
 kthread+0x436/0x520 kernel/kthread.c:334
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
 </TASK>
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 4322 Comm: syz.0.17 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
RIP: 0010:ntfs_compress_write+0x6b3/0x1c30 fs/ntfs3/file.c:923
Code: c1 fe 48 89 8c 24 e0 00 00 00 48 89 94 24 d8 00 00 00 48 8d 04 d5 f8 ff ff ff 48 89 44 24 18 c7 84 24 40 01 00 00 00 00 00 00 <c7> 84 24 50 01 00 00 00 00 00 00 80 7c 24 07 3f 0f 87 2d 06 00 00
RSP: 0018:ffffc9000313faa0 EFLAGS: 00000293
RAX: ffffffff8295fa51 RBX: 0000000000000000 RCX: ffff888025989dc0
RDX: 0000000000000000 RSI: 000000000000000c RDI: 0000000000000040
RBP: ffffc9000313fc58 R08: dffffc0000000000 R09: ffffed100bef2dfd
R10: ffffed100bef2dfd R11: 1ffff1100bef2dfc R12: dffffc0000000000
R13: ffffc9000313fd68 R14: 000000000000000c R15: 000000000000e000
FS:  00007f3d8a6a66c0(0000) GS:ffff8880b9100000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000055ae3e7b0048 CR3: 000000001f278000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 ntfs_file_write_iter+0x3d7/0x590 fs/ntfs3/file.c:1146
 call_write_iter include/linux/fs.h:2173 [inline]
 new_sync_write fs/read_write.c:507 [inline]
 vfs_write+0x712/0xd00 fs/read_write.c:594
 ksys_write+0x14d/0x250 fs/read_write.c:647
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7f3d8b037749
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:00007f3d8a6a6038 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f3d8b28dfa0 RCX: 00007f3d8b037749
RDX: 0000000000000020 RSI: 0000200000000980 RDI: 0000000000000005
RBP: 00007f3d8b0bbf91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f3d8b28e038 R14: 00007f3d8b28dfa0 R15: 00007fff657e1488
 </TASK>

Crashes (11):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/01/15 07:20 linux-5.15.y 68efe5a6c16a d6526ea3 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro] ci2-linux-5-15-kasan INFO: task hung in ntfs_fallocate
2026/01/15 03:44 linux-5.15.y 68efe5a6c16a d6526ea3 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro] ci2-linux-5-15-kasan INFO: task hung in ntfs_fallocate
2026/01/15 00:11 linux-5.15.y 68efe5a6c16a d6526ea3 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro] ci2-linux-5-15-kasan INFO: task hung in ntfs_fallocate
2026/01/14 20:33 linux-5.15.y 68efe5a6c16a d6526ea3 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro] ci2-linux-5-15-kasan INFO: task hung in ntfs_fallocate
2026/01/14 16:31 linux-5.15.y 68efe5a6c16a d6526ea3 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro] ci2-linux-5-15-kasan INFO: task hung in ntfs_fallocate
2026/01/14 12:28 linux-5.15.y 68efe5a6c16a d6526ea3 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro] ci2-linux-5-15-kasan INFO: task hung in ntfs_fallocate
2026/01/14 03:12 linux-5.15.y 68efe5a6c16a d6526ea3 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro] ci2-linux-5-15-kasan INFO: task hung in ntfs_fallocate
2026/01/13 22:52 linux-5.15.y 68efe5a6c16a d6526ea3 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro] ci2-linux-5-15-kasan INFO: task hung in ntfs_fallocate
2026/01/13 18:30 linux-5.15.y 68efe5a6c16a d6526ea3 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro] ci2-linux-5-15-kasan INFO: task hung in ntfs_fallocate
2026/01/13 13:55 linux-5.15.y 68efe5a6c16a d6526ea3 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro] ci2-linux-5-15-kasan INFO: task hung in ntfs_fallocate
2026/01/13 10:08 linux-5.15.y 68efe5a6c16a d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan INFO: task hung in ntfs_fallocate
* Struck through repros no longer work on HEAD.