Re: [syzbot] [ntfs3?] possible deadlock in ntfs_file_mmap_prepare

From: Hillf Danton
Date: Tue Jun 24 2025 - 20:37:48 EST

On Tue, 24 Jun 2025 11:51:29 -0700
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit: 5d4809e25903 Add linux-next specific files for 20250620
> git tree: linux-next
> console output: https://syzkaller.appspot.com/x/log.txt?x=17c65b0c580000
> kernel config: https://syzkaller.appspot.com/x/.config?x=58afc4b78b52b7e3
> dashboard link: https://syzkaller.appspot.com/bug?extid=a5d1c9dfa91705cd2f6d
> compiler: Debian clang version 20.1.6 (++20250514063057+1e4d39e07757-1~exp1~20250514183223.118), Debian LLD 20.1.6
> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1776a182580000
> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=17762dd4580000
>
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/16492bf6b788/disk-5d4809e2.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/7be284ded1de/vmlinux-5d4809e2.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/467d717f0d9c/bzImage-5d4809e2.xz
> mounted in repro #1: https://storage.googleapis.com/syzbot-assets/6f34591c3e45/mount_0.gz
> mounted in repro #2: https://storage.googleapis.com/syzbot-assets/d137199587c7/mount_3.gz
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+a5d1c9dfa91705cd2f6d@xxxxxxxxxxxxxxxxxxxxxxxxx
>
> loop0: detected capacity change from 0 to 4096
> ======================================================
> WARNING: possible circular locking dependency detected
> 6.16.0-rc2-next-20250620-syzkaller #0 Not tainted
> ------------------------------------------------------
> syz-executor414/5843 is trying to acquire lock:
> ffff8880739bcd08 (&sb->s_type->i_mutex_key#15){+.+.}-{4:4}, at: inode_lock include/linux/fs.h:869 [inline]
> ffff8880739bcd08 (&sb->s_type->i_mutex_key#15){+.+.}-{4:4}, at: ntfs_file_mmap_prepare+0x599/0x770 fs/ntfs3/file.c:314
>
> but task is already holding lock:
> ffff888023ca6d60 (&mm->mmap_lock){++++}-{4:4}, at: mmap_write_lock_killable include/linux/mmap_lock.h:374 [inline]
> ffff888023ca6d60 (&mm->mmap_lock){++++}-{4:4}, at: vm_mmap_pgoff+0x1bd/0x4c0 mm/util.c:577
>
> which lock already depends on the new lock.
>
>
> the existing dependency chain (in reverse order) is:
>
> -> #1 (&mm->mmap_lock){++++}-{4:4}:
> lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5871
> gup_fast_fallback+0x22e/0x2270 mm/gup.c:3366
> iov_iter_extract_user_pages lib/iov_iter.c:1846 [inline]
> iov_iter_extract_pages+0x35a/0x5e0 lib/iov_iter.c:1909
> dio_refill_pages fs/direct-io.c:172 [inline]
> dio_get_page fs/direct-io.c:213 [inline]
> do_direct_IO fs/direct-io.c:915 [inline]
> __blockdev_direct_IO+0x1166/0x3490 fs/direct-io.c:1243
> blockdev_direct_IO include/linux/fs.h:3497 [inline]
> ntfs_direct_IO+0x20b/0x410 fs/ntfs3/inode.c:813
> generic_file_read_iter+0x319/0x510 mm/filemap.c:2881
> do_iter_readv_writev+0x56b/0x7f0 fs/read_write.c:-1
> vfs_readv+0x253/0x850 fs/read_write.c:1018
> do_preadv fs/read_write.c:1132 [inline]
> __do_sys_preadv2 fs/read_write.c:1191 [inline]
> __se_sys_preadv2+0x179/0x290 fs/read_write.c:1182
> do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
> do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
> entry_SYSCALL_64_after_hwframe+0x77/0x7f
>
> -> #0 (&sb->s_type->i_mutex_key#15){+.+.}-{4:4}:
> check_prev_add kernel/locking/lockdep.c:3168 [inline]
> check_prevs_add kernel/locking/lockdep.c:3287 [inline]
> validate_chain+0xb9b/0x2140 kernel/locking/lockdep.c:3911
> __lock_acquire+0xab9/0xd20 kernel/locking/lockdep.c:5240
> lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5871
> down_write+0x96/0x1f0 kernel/locking/rwsem.c:1577
> inode_lock include/linux/fs.h:869 [inline]
> ntfs_file_mmap_prepare+0x599/0x770 fs/ntfs3/file.c:314

The bad on the ntfs3 side given locking order [3]
*
* ->i_rwsem (generic_perform_write)
* ->mmap_lock (fault_in_readable->do_page_fault)
*
[3] https://web.git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/mm/filemap.c#n100

> vfs_mmap_prepare include/linux/fs.h:2294 [inline]
> call_mmap_prepare mm/vma.c:2585 [inline]
> __mmap_region mm/vma.c:2657 [inline]
> mmap_region+0xb4a/0x2080 mm/vma.c:2746
> do_mmap+0xc45/0x10d0 mm/mmap.c:561
> vm_mmap_pgoff+0x31b/0x4c0 mm/util.c:579
> ksys_mmap_pgoff+0x51f/0x760 mm/mmap.c:607
> do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
> do_syscall_64+0xfa/0x3b0 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(&mm->mmap_lock);
> lock(&sb->s_type->i_mutex_key#15);
> lock(&mm->mmap_lock);
> lock(&sb->s_type->i_mutex_key#15);
>
> *** DEADLOCK ***
>
> 1 lock held by syz-executor414/5843:
> #0: ffff888023ca6d60 (&mm->mmap_lock){++++}-{4:4}, at: mmap_write_lock_killable include/linux/mmap_lock.h:374 [inline]
> #0: ffff888023ca6d60 (&mm->mmap_lock){++++}-{4:4}, at: vm_mmap_pgoff+0x1bd/0x4c0 mm/util.c:577
>
> stack backtrace:
> CPU: 1 UID: 0 PID: 5843 Comm: syz-executor414 Not tainted 6.16.0-rc2-next-20250620-syzkaller #0 PREEMPT(full)
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
> Call Trace:
> <TASK>
> dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
> print_circular_bug+0x2ee/0x310 kernel/locking/lockdep.c:2046
> check_noncircular+0x134/0x160 kernel/locking/lockdep.c:2178
> check_prev_add kernel/locking/lockdep.c:3168 [inline]
> check_prevs_add kernel/locking/lockdep.c:3287 [inline]
> validate_chain+0xb9b/0x2140 kernel/locking/lockdep.c:3911
> __lock_acquire+0xab9/0xd20 kernel/locking/lockdep.c:5240
> lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5871
> down_write+0x96/0x1f0 kernel/locking/rwsem.c:1577
> inode_lock include/linux/fs.h:869 [inline]
> ntfs_file_mmap_prepare+0x599/0x770 fs/ntfs3/file.c:314
> vfs_mmap_prepare include/linux/fs.h:2294 [inline]
> call_mmap_prepare mm/vma.c:2585 [inline]
> __mmap_region mm/vma.c:2657 [inline]
> mmap_region+0xb4a/0x2080 mm/vma.c:2746
> do_mmap+0xc45/0x10d0 mm/mmap.c:561
> vm_mmap_pgoff+0x31b/0x4c0 mm/util.c:579
> ksys_mmap_pgoff+0x51f/0x760 mm/mmap.c:607
> do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
> do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
> entry_SYSCALL_64_after_hwframe+0x77/0x7f
> RIP: 0033:0x7fd3b0279469
> Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 21 18 00 00 90 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 b8 ff ff ff f7 d8 64 89 01 48
> RSP: 002b:00007fff0b2f7dd8 EFLAGS: 00000246 ORIG_RAX: 0000000000000009
> RAX: ffffffffffffffda RBX: 0000200000000080 RCX: 00007fd3b0279469
> RDX: 000000000000000e RSI: 0000000000001000 RDI: 0000200000001000
> RBP: 00002000000000c0 R08: 0000000000000005 R09: 0000000000000000
> R10: 0000000000000011 R11: 0000000000000246 R12: 0031656c69662f2e
> R13: 0000200000000040 R14: 431bde82d7b634db R15: 00007fff0b2f7e40
> </TASK>
>
>
> ---
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