syzbot


possible deadlock in filemap_fault

Status: upstream: reported on 2025/07/04 02:22
Reported-by: syzbot+3af3cc7d946064c16d6f@syzkaller.appspotmail.com
First crash: 12d, last: 11d
Similar bugs (5)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-5.15 possible deadlock in filemap_fault 4 84 676d 851d 0/3 auto-obsoleted due to no activity on 2023/11/17 20:19
upstream possible deadlock in filemap_fault mm 4 C done 2884 18h15m 985d 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 error 140 1d02h 571d 0/3 upstream: reported C repro on 2023/12/22 21:26
linux-6.1 possible deadlock in filemap_fault 4 192 678d 853d 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 58 3d05h 465d 0/3 upstream: reported C repro on 2024/04/06 04:54

Sample crash report:
ntfs3: loop5: Failed to load $Extend (-2).
ntfs3: loop5: Failed to initialize $Extend.
======================================================
WARNING: possible circular locking dependency detected
6.6.95-syzkaller #0 Not tainted
------------------------------------------------------
syz.5.415/7972 is trying to acquire lock:
ffff88805dc71b60 (mapping.invalidate_lock#4){++++}-{3:3}, at: filemap_invalidate_lock_shared include/linux/fs.h:859 [inline]
ffff88805dc71b60 (mapping.invalidate_lock#4){++++}-{3:3}, at: filemap_fault+0x5db/0x15a0 mm/filemap.c:3330

but task is already holding lock:
ffff88807ee11e20 (&mm->mmap_lock){++++}-{3:3}, at: mmap_read_trylock include/linux/mmap_lock.h:165 [inline]
ffff88807ee11e20 (&mm->mmap_lock){++++}-{3:3}, at: get_mmap_lock_carefully mm/memory.c:5358 [inline]
ffff88807ee11e20 (&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+0x89d/0xbe0 fs/ntfs3/frecord.c:2060
       ntfs_fiemap+0xdb/0x130 fs/ntfs3/file.c:1213
       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/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:1120 [inline]
       ntfs_fallocate+0x7b2/0xfd0 fs/ntfs3/file.c:554
       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_read_fault mm/memory.c:4616 [inline]
       do_fault mm/memory.c:4753 [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+0x3886/0x4920 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
       do_strncpy_from_user lib/strncpy_from_user.c:-1 [inline]
       strncpy_from_user+0xff/0x2e0 lib/strncpy_from_user.c:139
       getname_flags+0xf6/0x500 fs/namei.c:151
       user_path_at_empty+0x2c/0x60 fs/namei.c:2908
       user_path_at include/linux/namei.h:57 [inline]
       path_listxattr+0xa3/0x1b0 fs/xattr.c:863
       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

other info that might help us debug this:

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

 Possible unsafe locking scenario:

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

 *** DEADLOCK ***

1 lock held by syz.5.415/7972:
 #0: ffff88807ee11e20 (&mm->mmap_lock){++++}-{3:3}, at: mmap_read_trylock include/linux/mmap_lock.h:165 [inline]
 #0: ffff88807ee11e20 (&mm->mmap_lock){++++}-{3:3}, at: get_mmap_lock_carefully mm/memory.c:5358 [inline]
 #0: ffff88807ee11e20 (&mm->mmap_lock){++++}-{3:3}, at: lock_mm_and_find_vma+0x32/0x300 mm/memory.c:5418

stack backtrace:
CPU: 0 PID: 7972 Comm: syz.5.415 Not tainted 6.6.95-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
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_read_fault mm/memory.c:4616 [inline]
 do_fault mm/memory.c:4753 [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+0x3886/0x4920 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: 0010:do_strncpy_from_user lib/strncpy_from_user.c:41 [inline]
RIP: 0010:strncpy_from_user+0xff/0x2e0 lib/strncpy_from_user.c:139
Code: 4c 89 ee e8 83 f7 33 fd 49 83 fd 07 0f 86 a1 00 00 00 4c 89 74 24 08 48 c7 44 24 10 f8 ff ff ff 45 31 e4 4c 89 3c 24 49 89 de <4f> 8b 3c 27 48 b8 ff fe fe fe fe fe fe fe 49 8d 1c 07 4c 89 fd 48
RSP: 0018:ffffc9000b527d90 EFLAGS: 00050246
RAX: ffffffff8451a31d RBX: ffff88801e6e2220 RCX: ffff88802bf93c00
RDX: 0000000000000002 RSI: 0000000000000fe0 RDI: 0000000000000007
RBP: 0000200000000100 R08: ffffea000079b807 R09: 1ffffd40000f3700
R10: dffffc0000000000 R11: fffff940000f3701 R12: 0000000000000000
R13: 0000000000000fe0 R14: ffff88801e6e2220 R15: 0000200000000100
 getname_flags+0xf6/0x500 fs/namei.c:151
 user_path_at_empty+0x2c/0x60 fs/namei.c:2908
 user_path_at include/linux/namei.h:57 [inline]
 path_listxattr+0xa3/0x1b0 fs/xattr.c:863
 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
RIP: 0033:0x7f8de058e929
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:00007f8de14df038 EFLAGS: 00000246 ORIG_RAX: 00000000000000c3
RAX: ffffffffffffffda RBX: 00007f8de07b5fa0 RCX: 00007f8de058e929
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000200000000100
RBP: 00007f8de0610b39 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f8de07b5fa0 R15: 00007ffc3bf1cc38
 </TASK>
----------------
Code disassembly (best guess):
   0:	4c 89 ee             	mov    %r13,%rsi
   3:	e8 83 f7 33 fd       	call   0xfd33f78b
   8:	49 83 fd 07          	cmp    $0x7,%r13
   c:	0f 86 a1 00 00 00    	jbe    0xb3
  12:	4c 89 74 24 08       	mov    %r14,0x8(%rsp)
  17:	48 c7 44 24 10 f8 ff 	movq   $0xfffffffffffffff8,0x10(%rsp)
  1e:	ff ff
  20:	45 31 e4             	xor    %r12d,%r12d
  23:	4c 89 3c 24          	mov    %r15,(%rsp)
  27:	49 89 de             	mov    %rbx,%r14
* 2a:	4f 8b 3c 27          	mov    (%r15,%r12,1),%r15 <-- trapping instruction
  2e:	48 b8 ff fe fe fe fe 	movabs $0xfefefefefefefeff,%rax
  35:	fe fe fe
  38:	49 8d 1c 07          	lea    (%r15,%rax,1),%rbx
  3c:	4c 89 fd             	mov    %r15,%rbp
  3f:	48                   	rex.W

Crashes (4):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/07/04 20:20 linux-6.6.y 3f5b4c104b7d d869b261 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan possible deadlock in filemap_fault
2025/07/04 05:09 linux-6.6.y 3f5b4c104b7d 76ad128c .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan possible deadlock in filemap_fault
2025/07/04 02:21 linux-6.6.y 3f5b4c104b7d 76ad128c .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan possible deadlock in filemap_fault
2025/07/04 02:21 linux-6.6.y 3f5b4c104b7d 76ad128c .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.