syzbot


possible deadlock in filemap_fault (2)

Status: upstream: reported on 2025/10/27 10:35
Reported-by: syzbot+1fdcfe1e229e0f2b423b@syzkaller.appspotmail.com
First crash: 53d, last: 32d
Similar bugs (6)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-6.6 possible deadlock in filemap_fault 4 4 168d 169d 0/2 auto-obsoleted due to no activity on 2025/10/12 20:21
linux-5.15 possible deadlock in filemap_fault 4 84 833d 1008d 0/3 auto-obsoleted due to no activity on 2023/11/17 20:19
upstream possible deadlock in filemap_fault mm 4 C done 2971 1d07h 1142d 0/29 upstream: reported C repro on 2022/11/03 22:14
linux-6.1 possible deadlock in filemap_fault (2) origin:upstream missing-backport 4 C inconclusive 156 20d 728d 0/3 upstream: reported C repro on 2023/12/22 21:26
linux-6.1 possible deadlock in filemap_fault 4 192 835d 1010d 0/3 auto-obsoleted due to no activity on 2023/11/15 23:38
linux-5.15 possible deadlock in filemap_fault (2) missing-backport origin:lts-only 4 C error 68 24d 623d 0/3 upstream: reported C repro on 2024/04/06 04:54

Sample crash report:
======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.0.5639/21025 is trying to acquire lock:
ffff88805d4d1400 (mapping.invalidate_lock#4){++++}-{3:3}, at: filemap_invalidate_lock_shared include/linux/fs.h:859 [inline]
ffff88805d4d1400 (mapping.invalidate_lock#4){++++}-{3:3}, at: filemap_fault+0x5db/0x15a0 mm/filemap.c:3330

but task is already holding lock:
ffff88806759cda0 (&mm->mmap_lock){++++}-{3:3}, at: mmap_read_trylock include/linux/mmap_lock.h:165 [inline]
ffff88806759cda0 (&mm->mmap_lock){++++}-{3:3}, at: get_mmap_lock_carefully mm/memory.c:5358 [inline]
ffff88806759cda0 (&mm->mmap_lock){++++}-{3:3}, at: lock_mm_and_find_vma+0x32/0x300 mm/memory.c:5418

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #2 (&mm->mmap_lock){++++}-{3:3}:
       __might_fault+0xc6/0x120 mm/memory.c:5946
       _copy_to_user+0x2a/0xa0 lib/usercopy.c:36
       copy_to_user include/linux/uaccess.h:191 [inline]
       fiemap_fill_next_extent+0x1c1/0x390 fs/ioctl.c:145
       ni_fiemap+0x392/0xbe0 fs/ntfs3/frecord.c:1948
       ntfs_fiemap+0xdb/0x130 fs/ntfs3/file.c:1216
       ioctl_fiemap fs/ioctl.c:220 [inline]
       do_vfs_ioctl+0x140c/0x1bb0 fs/ioctl.c:811
       __do_sys_ioctl fs/ioctl.c:869 [inline]
       __se_sys_ioctl+0x83/0x170 fs/ioctl.c:857
       do_syscall_x64 arch/x86/entry/common.c:51 [inline]
       do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
       entry_SYSCALL_64_after_hwframe+0x68/0xd2

-> #1 (&ni->ni_lock#2/5){+.+.}-{3:3}:
       __mutex_lock_common kernel/locking/mutex.c:603 [inline]
       __mutex_lock+0x129/0xcc0 kernel/locking/mutex.c:747
       ni_lock fs/ntfs3/ntfs_fs.h:1119 [inline]
       ntfs_fallocate+0x7b2/0xfd0 fs/ntfs3/file.c:557
       vfs_fallocate+0x58e/0x700 fs/open.c:324
       ksys_fallocate fs/open.c:347 [inline]
       __do_sys_fallocate fs/open.c:355 [inline]
       __se_sys_fallocate fs/open.c:353 [inline]
       __x64_sys_fallocate+0xc1/0x110 fs/open.c:353
       do_syscall_x64 arch/x86/entry/common.c:51 [inline]
       do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
       entry_SYSCALL_64_after_hwframe+0x68/0xd2

-> #0 (mapping.invalidate_lock#4){++++}-{3:3}:
       check_prev_add kernel/locking/lockdep.c:3134 [inline]
       check_prevs_add kernel/locking/lockdep.c:3253 [inline]
       validate_chain kernel/locking/lockdep.c:3869 [inline]
       __lock_acquire+0x2ddb/0x7c80 kernel/locking/lockdep.c:5137
       lock_acquire+0x197/0x410 kernel/locking/lockdep.c:5754
       down_read+0x46/0x2e0 kernel/locking/rwsem.c:1520
       filemap_invalidate_lock_shared include/linux/fs.h:859 [inline]
       filemap_fault+0x5db/0x15a0 mm/filemap.c:3330
       __do_fault+0x13b/0x4e0 mm/memory.c:4243
       do_shared_fault mm/memory.c:4683 [inline]
       do_fault mm/memory.c:4757 [inline]
       do_pte_missing mm/memory.c:3688 [inline]
       handle_pte_fault mm/memory.c:5025 [inline]
       __handle_mm_fault mm/memory.c:5166 [inline]
       handle_mm_fault+0x18f9/0x4920 mm/memory.c:5331
       do_user_addr_fault+0x738/0x12e0 arch/x86/mm/fault.c:1373
       handle_page_fault arch/x86/mm/fault.c:1465 [inline]
       exc_page_fault+0x67/0x110 arch/x86/mm/fault.c:1521
       asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:608

other info that might help us debug this:

Chain exists of:
  mapping.invalidate_lock#4 --> &ni->ni_lock#2/5 --> &mm->mmap_lock

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  rlock(&mm->mmap_lock);
                               lock(&ni->ni_lock#2/5);
                               lock(&mm->mmap_lock);
  rlock(mapping.invalidate_lock#4);

 *** DEADLOCK ***

1 lock held by syz.0.5639/21025:
 #0: ffff88806759cda0 (&mm->mmap_lock){++++}-{3:3}, at: mmap_read_trylock include/linux/mmap_lock.h:165 [inline]
 #0: ffff88806759cda0 (&mm->mmap_lock){++++}-{3:3}, at: get_mmap_lock_carefully mm/memory.c:5358 [inline]
 #0: ffff88806759cda0 (&mm->mmap_lock){++++}-{3:3}, at: lock_mm_and_find_vma+0x32/0x300 mm/memory.c:5418

stack backtrace:
CPU: 1 PID: 21025 Comm: syz.0.5639 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0x16c/0x230 lib/dump_stack.c:106
 check_noncircular+0x2bd/0x3c0 kernel/locking/lockdep.c:2187
 check_prev_add kernel/locking/lockdep.c:3134 [inline]
 check_prevs_add kernel/locking/lockdep.c:3253 [inline]
 validate_chain kernel/locking/lockdep.c:3869 [inline]
 __lock_acquire+0x2ddb/0x7c80 kernel/locking/lockdep.c:5137
 lock_acquire+0x197/0x410 kernel/locking/lockdep.c:5754
 down_read+0x46/0x2e0 kernel/locking/rwsem.c:1520
 filemap_invalidate_lock_shared include/linux/fs.h:859 [inline]
 filemap_fault+0x5db/0x15a0 mm/filemap.c:3330
 __do_fault+0x13b/0x4e0 mm/memory.c:4243
 do_shared_fault mm/memory.c:4683 [inline]
 do_fault mm/memory.c:4757 [inline]
 do_pte_missing mm/memory.c:3688 [inline]
 handle_pte_fault mm/memory.c:5025 [inline]
 __handle_mm_fault mm/memory.c:5166 [inline]
 handle_mm_fault+0x18f9/0x4920 mm/memory.c:5331
 do_user_addr_fault+0x738/0x12e0 arch/x86/mm/fault.c:1373
 handle_page_fault arch/x86/mm/fault.c:1465 [inline]
 exc_page_fault+0x67/0x110 arch/x86/mm/fault.c:1521
 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:608
RIP: 0033:0x7fe3b515758a
Code: 00 01 00 00 00 74 9a 83 f9 c0 0f 87 8c fe ff ff c5 fe 6f 4e 20 48 29 fe 48 83 c7 3f 49 8d 0c 10 48 83 e7 c0 48 01 fe 48 29 f9 <f3> a4 c4 c1 7e 7f 00 c4 c1 7e 7f 48 20 e9 0b fd ff ff 0f 1f 40 00
RSP: 002b:00007ffeba4cb128 EFLAGS: 00010202
RAX: 000020000000ac40 RBX: 0000000000000004 RCX: 000000000000559e
RDX: 000000000000559e RSI: 0000001b2bd3fe45 RDI: 000020000000ac40
RBP: 00007ffeba4cb1f8 R08: 000020000000ac40 R09: 0000000000000002
R10: 0000000000000000 R11: 0000000000000002 R12: 00007fe3b53e609c
R13: 00007fe3b53e6090 R14: fffffffffffffffe R15: 00007ffeba4cb240
 </TASK>

Crashes (3):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/11/17 11:21 linux-6.6.y 0a805b6ea8cd f7988ea4 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan possible deadlock in filemap_fault
2025/11/11 06:52 linux-6.6.y 0a805b6ea8cd 4e1406b4 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan possible deadlock in filemap_fault
2025/10/27 10:35 linux-6.6.y 4a243110dc88 c0460fcd .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan possible deadlock in filemap_fault
* Struck through repros no longer work on HEAD.