Re: [syzbot] possible deadlock in ni_fiemap

syzbot
2022-11-30T17:25:51Z

syzbot has found a reproducer for the following issue on:

HEAD commit: 01f856ae6d0c Merge tag 'net-6.1-rc8-2' of git://git.kernel..
git tree: upstream
console+strace: https://syzkaller.appspot.com/x/log.txt?x=15502883880000
kernel config: https://syzkaller.appspot.com/x/.config?x=2325e409a9a893e1
dashboard link: https://syzkaller.appspot.com/bug?extid=c300ab283ba3bc072439
compiler: Debian clang version 13.0.1-++20220126092033+75e33f71c2da-1~exp1~20220126212112.63, GNU ld (GNU Binutils for Debian) 2.35.2
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=161b2cf5880000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=125b2cbd880000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/5428d604f56a/disk-01f856ae.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/e953d290d254/vmlinux-01f856ae.xz
kernel image: https://storage.googleapis.com/syzbot-assets/3f71610a4904/bzImage-01f856ae.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/073a0bd8a341/mount_0.gz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+c300ab283ba3bc072439@syzkaller.appspotmail.com

loop0: detected capacity change from 0 to 4096
======================================================
WARNING: possible circular locking dependency detected
6.1.0-rc7-syzkaller-00101-g01f856ae6d0c #0 Not tainted
------------------------------------------------------
syz-executor911/3632 is trying to acquire lock:
ffff888021991718 (&mm->mmap_lock#2){++++}-{3:3}, at: __might_fault+0x8f/0x110 mm/memory.c:5645

but task is already holding lock:
ffff8880741101b0 (&ni->file.run_lock#3){++++}-{3:3}, at: ni_fiemap+0x32b/0x1130 fs/ntfs3/frecord.c:1947

which lock already depends on the new lock.

the existing dependency chain (in reverse order) is:

-> #1 (&ni->file.run_lock#3){++++}-{3:3}:
lock_acquire+0x182/0x3c0 kernel/locking/lockdep.c:5668
down_read+0x39/0x50 kernel/locking/rwsem.c:1509
attr_data_get_block+0x158/0x2370 fs/ntfs3/attrib.c:899
ntfs_file_mmap+0x48c/0x730 fs/ntfs3/file.c:387
call_mmap include/linux/fs.h:2204 [inline]
mmap_region+0xfe6/0x1e20 mm/mmap.c:2625
do_mmap+0x8d9/0xf30 mm/mmap.c:1412
vm_mmap_pgoff+0x19e/0x2b0 mm/util.c:520
ksys_mmap_pgoff+0x48c/0x6d0 mm/mmap.c:1458
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd

-> #0 (&mm->mmap_lock#2){++++}-{3:3}:
check_prev_add kernel/locking/lockdep.c:3097 [inline]
check_prevs_add kernel/locking/lockdep.c:3216 [inline]
validate_chain+0x1898/0x6ae0 kernel/locking/lockdep.c:3831
__lock_acquire+0x1292/0x1f60 kernel/locking/lockdep.c:5055
lock_acquire+0x182/0x3c0 kernel/locking/lockdep.c:5668
__might_fault+0xb2/0x110 mm/memory.c:5646
_copy_to_user+0x26/0x130 lib/usercopy.c:29
copy_to_user include/linux/uaccess.h:169 [inline]
fiemap_fill_next_extent+0x22e/0x410 fs/ioctl.c:144
ni_fiemap+0xa11/0x1130 fs/ntfs3/frecord.c:2051
ntfs_fiemap+0x134/0x180 fs/ntfs3/file.c:1245
ioctl_fiemap fs/ioctl.c:219 [inline]
do_vfs_ioctl+0x187f/0x29a0 fs/ioctl.c:810
__do_sys_ioctl fs/ioctl.c:868 [inline]
__se_sys_ioctl+0x83/0x170 fs/ioctl.c:856
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd

other info that might help us debug this:

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
lock(&ni->file.run_lock#3);
lock(&mm->mmap_lock#2);
lock(&ni->file.run_lock#3);
lock(&mm->mmap_lock#2);

*** DEADLOCK ***

2 locks held by syz-executor911/3632:
#0: ffff888074110100 (&ni->ni_lock/4){+.+.}-{3:3}, at: ni_lock fs/ntfs3/ntfs_fs.h:1108 [inline]
#0: ffff888074110100 (&ni->ni_lock/4){+.+.}-{3:3}, at: ntfs_fiemap+0x101/0x180 fs/ntfs3/file.c:1243
#1: ffff8880741101b0 (&ni->file.run_lock#3){++++}-{3:3}, at: ni_fiemap+0x32b/0x1130 fs/ntfs3/frecord.c:1947

stack backtrace:
CPU: 0 PID: 3632 Comm: syz-executor911 Not tainted 6.1.0-rc7-syzkaller-00101-g01f856ae6d0c #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/26/2022
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0x1b1/0x28e lib/dump_stack.c:106
check_noncircular+0x2cc/0x390 kernel/locking/lockdep.c:2177
check_prev_add kernel/locking/lockdep.c:3097 [inline]
check_prevs_add kernel/locking/lockdep.c:3216 [inline]
validate_chain+0x1898/0x6ae0 kernel/locking/lockdep.c:3831
__lock_acquire+0x1292/0x1f60 kernel/locking/lockdep.c:5055
lock_acquire+0x182/0x3c0 kernel/locking/lockdep.c:5668
__might_fault+0xb2/0x110 mm/memory.c:5646
_copy_to_user+0x26/0x130 lib/usercopy.c:29
copy_to_user include/linux/uaccess.h:169 [inline]
fiemap_fill_next_extent+0x22e/0x410 fs/ioctl.c:144
ni_fiemap+0xa11/0x1130 fs/ntfs3/frecord.c:2051
ntfs_fiemap+0x134/0x180 fs/ntfs3/file.c:1245
ioctl_fiemap fs/ioctl.c:219 [inline]
do_vfs_ioctl+0x187f/0x29a0 fs/ioctl.c:810
__do_sys_ioctl fs/ioctl.c:868 [inline]
__se_sys_ioctl+0x83/0x170 fs/ioctl.c:856
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7febc4d60d69
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 51 14 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 c0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fffe05c24d8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007febc4d60d69
RDX: 00000000200001c0 RSI: 00000000c020660b RDI: 00000000