syzbot


possible deadlock in page_cache_ra_order

Status: upstream: reported on 2026/05/31 02:05
Subsystems: mm fs
Labels: prio:high
[Documentation on labels]
Reported-by: syzbot+8bd419f88e25ab12cb75@syzkaller.appspotmail.com
First crash: 7d03h, last: 6d21h
✨ AI Jobs (1)
ID Workflow Result Correct Bug Created Started Finished Revision Error
6842e9d3-4123-4558-b23c-857df07c7b24 assessment-security DenialOfService: ❌ Exploitable: ❌ FilesystemTrigger: ✅ NetworkTrigger: ❌ PeripheralTrigger: ✅ RemoteTrigger: ❌ Unprivileged: ✅ UserNamespace: ✅ VMGuestTrigger: ❌ VMHostTrigger: ❌ possible deadlock in page_cache_ra_order 2026/05/29 22:51 2026/05/29 22:51 2026/05/29 23:47 6b4a844333e83556da95d61d7f207e7ef5cd4bc6
Discussions (1)
Title Replies (including bot) Last reply
[syzbot] [mm?] [fs?] possible deadlock in page_cache_ra_order 0 (1) 2026/05/31 02:05

Sample crash report:
loop4: detected capacity change from 0 to 4096
ntfs3(loop4): failed to convert "0080" to koi8-ru
======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.4.188/6496 is trying to acquire lock:
ffff888062d66830 (mapping.invalidate_lock#3){++++}-{4:4}, at: filemap_invalidate_lock_shared include/linux/fs.h:1089 [inline]
ffff888062d66830 (mapping.invalidate_lock#3){++++}-{4:4}, at: do_page_cache_ra mm/readahead.c:349 [inline]
ffff888062d66830 (mapping.invalidate_lock#3){++++}-{4:4}, at: page_cache_ra_order+0x2b4/0x4a0 mm/readahead.c:562

but task is already holding lock:
ffff88803fd78888 (&ni->ni_lock/5){+.+.}-{4:4}, at: ni_lock fs/ntfs3/ntfs_fs.h:1214 [inline]
ffff88803fd78888 (&ni->ni_lock/5){+.+.}-{4:4}, at: ntfs_readdir+0x6c9/0xf40 fs/ntfs3/dir.c:497

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (&ni->ni_lock/5){+.+.}-{4:4}:
       __mutex_lock_common kernel/locking/rtmutex_api.c:559 [inline]
       mutex_lock_nested+0x5a/0x1d0 kernel/locking/rtmutex_api.c:578
       ni_lock fs/ntfs3/ntfs_fs.h:1214 [inline]
       ntfs_fallocate+0x59f/0x1230 fs/ntfs3/file.c:543
       vfs_fallocate+0x672/0x7f0 fs/open.c:338
       ioctl_preallocate fs/ioctl.c:289 [inline]
       file_ioctl+0x64b/0x870 fs/ioctl.c:332
       do_vfs_ioctl+0xc29/0x1540 fs/ioctl.c:576
       __do_sys_ioctl fs/ioctl.c:595 [inline]
       __se_sys_ioctl+0x82/0x170 fs/ioctl.c:583
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #0 (mapping.invalidate_lock#3){++++}-{4:4}:
       check_prev_add kernel/locking/lockdep.c:3167 [inline]
       check_prevs_add kernel/locking/lockdep.c:3286 [inline]
       validate_chain kernel/locking/lockdep.c:3910 [inline]
       __lock_acquire+0x15a5/0x2d10 kernel/locking/lockdep.c:5239
       lock_acquire+0x106/0x350 kernel/locking/lockdep.c:5870
       down_read+0x97/0x200 kernel/locking/rwsem.c:1568
       filemap_invalidate_lock_shared include/linux/fs.h:1089 [inline]
       do_page_cache_ra mm/readahead.c:349 [inline]
       page_cache_ra_order+0x2b4/0x4a0 mm/readahead.c:562
       do_sync_mmap_readahead+0x698/0x7b0 mm/filemap.c:3409
       filemap_fault+0x790/0x13a0 mm/filemap.c:3559
       __do_fault+0x138/0x2a0 mm/memory.c:5421
       do_shared_fault mm/memory.c:5920 [inline]
       do_fault mm/memory.c:5994 [inline]
       do_pte_missing+0x65b/0x2940 mm/memory.c:4566
       handle_pte_fault mm/memory.c:6375 [inline]
       __handle_mm_fault mm/memory.c:6513 [inline]
       handle_mm_fault+0xdc2/0x14d0 mm/memory.c:6682
       do_user_addr_fault+0x75b/0x1340 arch/x86/mm/fault.c:1390
       handle_page_fault arch/x86/mm/fault.c:1479 [inline]
       exc_page_fault+0x6a/0xc0 arch/x86/mm/fault.c:1532
       asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:595
       filldir64+0x2b2/0x640 fs/readdir.c:368
       dir_emit include/linux/fs.h:3587 [inline]
       ntfs_dir_emit fs/ntfs3/dir.c:344 [inline]
       ntfs_read_hdr+0x8fb/0xc80 fs/ntfs3/dir.c:385
       ntfs_readdir+0x98e/0xf40 fs/ntfs3/dir.c:545
       iterate_dir+0x3a5/0x580 fs/readdir.c:110
       __do_sys_getdents64 fs/readdir.c:399 [inline]
       __se_sys_getdents64+0xf1/0x280 fs/readdir.c:384
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

other info that might help us debug this:

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&ni->ni_lock/5);
                               lock(mapping.invalidate_lock#3);
                               lock(&ni->ni_lock/5);
  rlock(mapping.invalidate_lock#3);

 *** DEADLOCK ***

3 locks held by syz.4.188/6496:
 #0: ffff888037dde928 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x252/0x320 fs/file.c:1260
 #1: ffff88803fd78b40 (&type->i_mutex_dir_key#10){++++}-{4:4}, at: iterate_dir+0x29e/0x580 fs/readdir.c:103
 #2: ffff88803fd78888 (&ni->ni_lock/5){+.+.}-{4:4}, at: ni_lock fs/ntfs3/ntfs_fs.h:1214 [inline]
 #2: ffff88803fd78888 (&ni->ni_lock/5){+.+.}-{4:4}, at: ntfs_readdir+0x6c9/0xf40 fs/ntfs3/dir.c:497

stack backtrace:
CPU: 0 UID: 0 PID: 6496 Comm: syz.4.188 Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 print_circular_bug+0x2e1/0x300 kernel/locking/lockdep.c:2045
 check_noncircular+0x12e/0x150 kernel/locking/lockdep.c:2177
 check_prev_add kernel/locking/lockdep.c:3167 [inline]
 check_prevs_add kernel/locking/lockdep.c:3286 [inline]
 validate_chain kernel/locking/lockdep.c:3910 [inline]
 __lock_acquire+0x15a5/0x2d10 kernel/locking/lockdep.c:5239
 lock_acquire+0x106/0x350 kernel/locking/lockdep.c:5870
 down_read+0x97/0x200 kernel/locking/rwsem.c:1568
 filemap_invalidate_lock_shared include/linux/fs.h:1089 [inline]
 do_page_cache_ra mm/readahead.c:349 [inline]
 page_cache_ra_order+0x2b4/0x4a0 mm/readahead.c:562
 do_sync_mmap_readahead+0x698/0x7b0 mm/filemap.c:3409
 filemap_fault+0x790/0x13a0 mm/filemap.c:3559
 __do_fault+0x138/0x2a0 mm/memory.c:5421
 do_shared_fault mm/memory.c:5920 [inline]
 do_fault mm/memory.c:5994 [inline]
 do_pte_missing+0x65b/0x2940 mm/memory.c:4566
 handle_pte_fault mm/memory.c:6375 [inline]
 __handle_mm_fault mm/memory.c:6513 [inline]
 handle_mm_fault+0xdc2/0x14d0 mm/memory.c:6682
 do_user_addr_fault+0x75b/0x1340 arch/x86/mm/fault.c:1390
 handle_page_fault arch/x86/mm/fault.c:1479 [inline]
 exc_page_fault+0x6a/0xc0 arch/x86/mm/fault.c:1532
 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:595
RIP: 0010:filldir64+0x2b2/0x640 fs/readdir.c:369
Code: 00 48 39 c8 48 0f 47 c1 0f 01 cb 48 8b 4c 24 28 48 89 48 08 48 bd 00 00 00 00 00 fc ff df 48 8b 44 24 60 48 89 02 8b 44 24 04 <66> 89 42 10 41 80 e7 0f 44 88 7a 12 42 c6 44 2a 13 00 48 89 54 24
RSP: 0018:ffffc9000e517aa8 EFLAGS: 00050287
RAX: 0000000000000020 RBX: ffffc9000e517e38 RCX: 00000000000008c0
RDX: 0000200000000ff0 RSI: 0000000000000a29 RDI: 0000000000000a2a
RBP: dffffc0000000000 R08: 0000000000000000 R09: 0000000000000000
R10: dffffc0000000000 R11: ffffed10054a03e1 R12: ffff88802699c000
R13: 0000000000000009 R14: 0000000000000009 R15: 0000000000000008
 dir_emit include/linux/fs.h:3587 [inline]
 ntfs_dir_emit fs/ntfs3/dir.c:344 [inline]
 ntfs_read_hdr+0x8fb/0xc80 fs/ntfs3/dir.c:385
 ntfs_readdir+0x98e/0xf40 fs/ntfs3/dir.c:545
 iterate_dir+0x3a5/0x580 fs/readdir.c:110
 __do_sys_getdents64 fs/readdir.c:399 [inline]
 __se_sys_getdents64+0xf1/0x280 fs/readdir.c:384
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7feadcacce59
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 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 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007feadad1e028 EFLAGS: 00000246 ORIG_RAX: 00000000000000d9
RAX: ffffffffffffffda RBX: 00007feadcd45fa0 RCX: 00007feadcacce59
RDX: 00000000000000e0 RSI: 0000200000000fc0 RDI: 0000000000000006
RBP: 00007feadcb62d6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007feadcd46038 R14: 00007feadcd45fa0 R15: 00007ffebb7a32a8
 </TASK>
ntfs3(loop4): failed to convert name for inode 1e.
ntfs3(loop4): ino=1f, mi_enum_attr
----------------
Code disassembly (best guess):
   0:	00 48 39             	add    %cl,0x39(%rax)
   3:	c8 48 0f 47          	enter  $0xf48,$0x47
   7:	c1 0f 01             	rorl   $0x1,(%rdi)
   a:	cb                   	lret
   b:	48 8b 4c 24 28       	mov    0x28(%rsp),%rcx
  10:	48 89 48 08          	mov    %rcx,0x8(%rax)
  14:	48 bd 00 00 00 00 00 	movabs $0xdffffc0000000000,%rbp
  1b:	fc ff df
  1e:	48 8b 44 24 60       	mov    0x60(%rsp),%rax
  23:	48 89 02             	mov    %rax,(%rdx)
  26:	8b 44 24 04          	mov    0x4(%rsp),%eax
* 2a:	66 89 42 10          	mov    %ax,0x10(%rdx) <-- trapping instruction
  2e:	41 80 e7 0f          	and    $0xf,%r15b
  32:	44 88 7a 12          	mov    %r15b,0x12(%rdx)
  36:	42 c6 44 2a 13 00    	movb   $0x0,0x13(%rdx,%r13,1)
  3c:	48                   	rex.W
  3d:	89                   	.byte 0x89
  3e:	54                   	push   %rsp
  3f:	24                   	.byte 0x24

Crashes (5):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/05/27 07:58 linux-next e7e28506af98 2b01f00e .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-linux-next-kasan-gce-root possible deadlock in page_cache_ra_order
2026/05/27 07:55 linux-next e7e28506af98 2b01f00e .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-linux-next-kasan-gce-root possible deadlock in page_cache_ra_order
2026/05/27 07:54 linux-next e7e28506af98 2b01f00e .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-linux-next-kasan-gce-root possible deadlock in page_cache_ra_order
2026/05/27 07:54 linux-next e7e28506af98 2b01f00e .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-linux-next-kasan-gce-root possible deadlock in page_cache_ra_order
2026/05/27 01:58 linux-next e7e28506af98 2b01f00e .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-linux-next-kasan-gce-root possible deadlock in page_cache_ra_order
* Struck through repros no longer work on HEAD.