[syzbot] [mm?] [fs?] possible deadlock in page_cache_ra_order

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: e7e28506af98 Add linux-next specific files for 20260526
git tree: linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=1377f67e580000
kernel config: https://syzkaller.appspot.com/x/.config?x=e1701da6552dd9b8
dashboard link: https://syzkaller.appspot.com/bug?extid=8bd419f88e25ab12cb75
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/0060088615f7/disk-e7e28506.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/bee8a0723af7/vmlinux-e7e28506.xz
kernel image: https://storage.googleapis.com/syzbot-assets/040209574106/bzImage-e7e28506.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+8bd419...@syzkaller.appspotmail.com

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


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