From: syzbot <syzbot+cfc6e8106bec1c524f7d@syzkaller.appspotmail.com>
To: almaz.alexandrovich@paragon-software.com, gality369@gmail.com,
linux-kernel@vger.kernel.org, ntfs3@lists.linux.dev,
syzkaller-bugs@googlegroups.com
Subject: Re: [syzbot] [ntfs3?] possible deadlock in ntfs_readdir
Date: Tue, 13 Oct 2026 06:53:37 -0700 [thread overview]
Message-ID: <6ace37e1.0e5b5d80.2c029c.06da.GAE@google.com> (raw)
In-Reply-To: <6a42cfca.9dc7bc9d.3393b4.0008.GAE@google.com>
syzbot has found a reproducer for the following issue on:
HEAD commit: 24a19b953e2a Linux 7.3-rc7
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=118a55c9580000
kernel config: https://syzkaller.appspot.com/x/.config?x=df4bbab1c2172b9f
dashboard link: https://syzkaller.appspot.com/bug?extid=cfc6e8106bec1c524f7d
compiler: Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1575d40d580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=14f68dd1580000
Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/71ab5ff0ed88/disk-24a19b95.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/f5849c6ea337/vmlinux-24a19b95.xz
kernel image: https://storage.googleapis.com/syzbot-assets/cf747b187062/bzImage-24a19b95.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/dd39b95ec4ba/mount_0.gz
The issue was bisected to:
commit d62cf685d12e95cc0a4122c43cd9f0eb8bba0b4c
Author: ZhengYuan Huang <gality369@gmail.com>
Date: Mon Apr 27 07:26:50 2026 +0000
fs/ntfs3: hold ni_lock across readdir metadata walk
bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=1376eb49580000
final oops: https://syzkaller.appspot.com/x/report.txt?x=10f6eb49580000
console output: https://syzkaller.appspot.com/x/log.txt?x=1776eb49580000
IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+cfc6e8106bec1c524f7d@syzkaller.appspotmail.com
Fixes: d62cf685d12e ("fs/ntfs3: hold ni_lock across readdir metadata walk")
ntfs3(loop1): failed to convert "c46c" to cp855
ntfs3(loop1): ino=20, mi_enum_attr
======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.1.40/6092 is trying to acquire lock:
ffff88803a8344b8 (&mm->mmap_lock){++++}-{4:4}, at: mmap_read_lock_killable+0x1d/0x70 include/linux/mmap_lock.h:609
but task is already holding lock:
ffff88805ecb73c8 (&ni->ni_lock/5){+.+.}-{4:4}, at: ni_lock fs/ntfs3/ntfs_fs.h:1247 [inline]
ffff88805ecb73c8 (&ni->ni_lock/5){+.+.}-{4:4}, at: ntfs_readdir+0x717/0xf70 fs/ntfs3/dir.c:541
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:561 [inline]
mutex_lock_nested+0x5a/0x1d0 kernel/locking/rtmutex_api.c:580
ni_lock fs/ntfs3/ntfs_fs.h:1247 [inline]
attr_data_get_block+0x1cd/0x2c0 fs/ntfs3/attrib.c:976
ntfs_file_mmap_prepare+0x5b3/0xa20 fs/ntfs3/file.c:430
vfs_mmap_prepare include/linux/fs.h:2071 [inline]
call_mmap_prepare mm/vma.c:2799 [inline]
__mmap_region mm/vma.c:2888 [inline]
mmap_region+0xebb/0x25c0 mm/vma.c:2989
do_mmap+0xe0e/0x1310 mm/mmap.c:573
vm_mmap_pgoff+0x275/0x4e0 mm/util.c:581
ksys_mmap_pgoff+0x4a6/0x720 mm/mmap.c:619
do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84
entry_SYSCALL_64_after_hwframe+0x77/0x7f
-> #0 (&mm->mmap_lock){++++}-{4:4}:
check_prev_add kernel/locking/lockdep.c:3209 [inline]
check_prevs_add kernel/locking/lockdep.c:3328 [inline]
validate_chain kernel/locking/lockdep.c:3952 [inline]
__lock_acquire+0x164c/0x2de0 kernel/locking/lockdep.c:5288
lock_acquire+0x115/0x350 kernel/locking/lockdep.c:5942
down_read_killable+0xa4/0x220 kernel/locking/rwsem.c:1599
mmap_read_lock_killable+0x1d/0x70 include/linux/mmap_lock.h:609
get_mmap_lock_carefully mm/mmap_lock.c:450 [inline]
lock_mm_and_find_vma+0x2d6/0x340 mm/mmap_lock.c:501
do_user_addr_fault+0x343/0x1340 arch/x86/mm/fault.c:1366
handle_page_fault arch/x86/mm/fault.c:1483 [inline]
exc_page_fault+0x6a/0xc0 arch/x86/mm/fault.c:1536
asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:595
stac arch/x86/include/asm/smap.h:-1 [inline]
filldir+0x29f/0x630 fs/readdir.c:291
dir_emit include/linux/fs.h:3610 [inline]
ntfs_dir_emit fs/ntfs3/dir.c:388 [inline]
ntfs_read_hdr+0x8a7/0xc10 fs/ntfs3/dir.c:429
ntfs_readdir+0x9ab/0xf70 fs/ntfs3/dir.c:589
iterate_dir+0x3ea/0x8a0 fs/readdir.c:114
__do_sys_getdents fs/readdir.c:324 [inline]
__se_sys_getdents+0xf1/0x270 fs/readdir.c:309
do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84
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(&mm->mmap_lock);
lock(&ni->ni_lock/5);
rlock(&mm->mmap_lock);
*** DEADLOCK ***
locks held by syz.1.40/6092: 3, last CPU#0:
#0: ffff888037c3c328 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x252/0x320 fs/file.c:1259
#1: ffff88805ecb7690 (&type->i_mutex_dir_key#8){++++}-{4:4}, at: iterate_dir+0x293/0x8a0 fs/readdir.c:106
#2: ffff88805ecb73c8 (&ni->ni_lock/5){+.+.}-{4:4}, at: ni_lock fs/ntfs3/ntfs_fs.h:1247 [inline]
#2: ffff88805ecb73c8 (&ni->ni_lock/5){+.+.}-{4:4}, at: ntfs_readdir+0x717/0xf70 fs/ntfs3/dir.c:541
stack backtrace:
CPU: 0 UID: 0 PID: 6092 Comm: syz.1.40 Not tainted syzkaller #0 PREEMPT_{RT,(full)}
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Call Trace:
<TASK>
dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
print_circular_bug+0x2e2/0x300 kernel/locking/lockdep.c:2087
check_noncircular+0x12f/0x150 kernel/locking/lockdep.c:2219
check_prev_add kernel/locking/lockdep.c:3209 [inline]
check_prevs_add kernel/locking/lockdep.c:3328 [inline]
validate_chain kernel/locking/lockdep.c:3952 [inline]
__lock_acquire+0x164c/0x2de0 kernel/locking/lockdep.c:5288
lock_acquire+0x115/0x350 kernel/locking/lockdep.c:5942
down_read_killable+0xa4/0x220 kernel/locking/rwsem.c:1599
mmap_read_lock_killable+0x1d/0x70 include/linux/mmap_lock.h:609
get_mmap_lock_carefully mm/mmap_lock.c:450 [inline]
lock_mm_and_find_vma+0x2d6/0x340 mm/mmap_lock.c:501
do_user_addr_fault+0x343/0x1340 arch/x86/mm/fault.c:1366
handle_page_fault arch/x86/mm/fault.c:1483 [inline]
exc_page_fault+0x6a/0xc0 arch/x86/mm/fault.c:1536
asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:595
RIP: 0010:filldir+0x29f/0x630 fs/readdir.c:293
Code: df 49 29 ef 48 b8 00 f0 ff ff ff 7f 00 00 49 39 c7 4c 0f 47 f8 bf 07 00 00 00 44 89 f6 e8 09 5b 7e ff 0f 01 cb 48 8b 44 24 20 <49> 89 47 08 48 bd 00 00 00 00 00 fc ff df 48 8b 44 24 40 48 89 03
RSP: 0018:ffffc90004f1fab0 EFLAGS: 00050293
RAX: 00000000000015a0 RBX: 0000200000008578 RCX: ffff888032ec1f40
RDX: 0000000000000000 RSI: 0000000000000005 RDI: 0000000000000007
RBP: 0000000000000020 R08: 0000000000000000 R09: 0000000000000000
R10: dffffc0000000000 R11: ffffed10065d83e9 R12: ffff88803c9f4000
R13: 0000000000000005 R14: 0000000000000005 R15: 0000200000008558
dir_emit include/linux/fs.h:3610 [inline]
ntfs_dir_emit fs/ntfs3/dir.c:388 [inline]
ntfs_read_hdr+0x8a7/0xc10 fs/ntfs3/dir.c:429
ntfs_readdir+0x9ab/0xf70 fs/ntfs3/dir.c:589
iterate_dir+0x3ea/0x8a0 fs/readdir.c:114
__do_sys_getdents fs/readdir.c:324 [inline]
__se_sys_getdents+0xf1/0x270 fs/readdir.c:309
do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f210f74e2d9
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:00007f210edae028 EFLAGS: 00000246 ORIG_RAX: 000000000000004e
RAX: ffffffffffffffda RBX: 00007f210f9d5fa0 RCX: 00007f210f74e2d9
RDX: 00000000000000b8 RSI: 0000200000008500 RDI: 0000000000000005
RBP: 00007f210f7e5888 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f210f9d6038 R14: 00007f210f9d5fa0 R15: 00007fff702375e8
</TASK>
----------------
Code disassembly (best guess):
0: df 49 29 fisttps 0x29(%rcx)
3: ef out %eax,(%dx)
4: 48 b8 00 f0 ff ff ff movabs $0x7ffffffff000,%rax
b: 7f 00 00
e: 49 39 c7 cmp %rax,%r15
11: 4c 0f 47 f8 cmova %rax,%r15
15: bf 07 00 00 00 mov $0x7,%edi
1a: 44 89 f6 mov %r14d,%esi
1d: e8 09 5b 7e ff call 0xff7e5b2b
22: 0f 01 cb stac
25: 48 8b 44 24 20 mov 0x20(%rsp),%rax
* 2a: 49 89 47 08 mov %rax,0x8(%r15) <-- trapping instruction
2e: 48 bd 00 00 00 00 00 movabs $0xdffffc0000000000,%rbp
35: fc ff df
38: 48 8b 44 24 40 mov 0x40(%rsp),%rax
3d: 48 89 03 mov %rax,(%rbx)
---
If you want syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
If you attach or paste a git patch, syzbot will apply it before testing.
prev parent reply other threads:[~2026-10-13 13:53 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-06-29 20:04 syzbot
2026-08-02 3:39 ` syzbot
2026-09-05 23:39 ` syzbot
2026-10-13 13:53 ` syzbot [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=6ace37e1.0e5b5d80.2c029c.06da.GAE@google.com \
--to=syzbot+cfc6e8106bec1c524f7d@syzkaller.appspotmail.com \
--cc=almaz.alexandrovich@paragon-software.com \
--cc=gality369@gmail.com \
--cc=linux-kernel@vger.kernel.org \
--cc=ntfs3@lists.linux.dev \
--cc=syzkaller-bugs@googlegroups.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox
all inboxes | Powered by JetHome®