Hello,
syzbot found the following issue on:
HEAD commit: e5eb28f6d1af Merge tag 'mm-nonmm-stable-2024-03-14-09-36' ..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=160dc26e180000
kernel config: https://syzkaller.appspot.com/x/.config?x=4ffb854606e658d
dashboard link: https://syzkaller.appspot.com/bug?extid=49056626fe41e01f2ba7
compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=10f467b9180000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=173b7ac9180000
Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/7bc7510fe41f/non_bootable_disk-e5eb28f6.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/a5c7ad05d6b2/vmlinux-e5eb28f6.xz
kernel image: https://storage.googleapis.com/syzbot-assets/531cb1917612/bzImage-e5eb28f6.xz
IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: [email protected]
============================================
WARNING: possible recursive locking detected
6.8.0-syzkaller-09791-ge5eb28f6d1af #0 Not tainted
--------------------------------------------
syz-executor258/5169 is trying to acquire lock:
ffff88802a6d23d0 (&vma->vm_lock->lock){++++}-{3:3}, at: uffd_move_lock mm/userfaultfd.c:1447 [inline]
ffff88802a6d23d0 (&vma->vm_lock->lock){++++}-{3:3}, at: move_pages+0xbab/0x4970 mm/userfaultfd.c:1583
but task is already holding lock:
ffff88802a6d2580 (&vma->vm_lock->lock){++++}-{3:3}, at: uffd_move_lock mm/userfaultfd.c:1445 [inline]
ffff88802a6d2580 (&vma->vm_lock->lock){++++}-{3:3}, at: move_pages+0xb6f/0x4970 mm/userfaultfd.c:1583
other info that might help us debug this:
Possible unsafe locking scenario:
CPU0
----
lock(&vma->vm_lock->lock);
lock(&vma->vm_lock->lock);
*** DEADLOCK ***
May be due to missing lock nesting notation
2 locks held by syz-executor258/5169:
#0: ffff888015086a20 (&mm->mmap_lock){++++}-{3:3}, at: mmap_read_lock include/linux/mmap_lock.h:146 [inline]
#0: ffff888015086a20 (&mm->mmap_lock){++++}-{3:3}, at: uffd_move_lock mm/userfaultfd.c:1438 [inline]
#0: ffff888015086a20 (&mm->mmap_lock){++++}-{3:3}, at: move_pages+0x8df/0x4970 mm/userfaultfd.c:1583
#1: ffff88802a6d2580 (&vma->vm_lock->lock){++++}-{3:3}, at: uffd_move_lock mm/userfaultfd.c:1445 [inline]
#1: ffff88802a6d2580 (&vma->vm_lock->lock){++++}-{3:3}, at: move_pages+0xb6f/0x4970 mm/userfaultfd.c:1583
stack backtrace:
CPU: 2 PID: 5169 Comm: syz-executor258 Not tainted 6.8.0-syzkaller-09791-ge5eb28f6d1af #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:114
check_deadlock kernel/locking/lockdep.c:3062 [inline]
validate_chain kernel/locking/lockdep.c:3856 [inline]
__lock_acquire+0x20e6/0x3b30 kernel/locking/lockdep.c:5137
lock_acquire kernel/locking/lockdep.c:5754 [inline]
lock_acquire+0x1b1/0x540 kernel/locking/lockdep.c:5719
down_read+0x9a/0x330 kernel/locking/rwsem.c:1526
uffd_move_lock mm/userfaultfd.c:1447 [inline]
move_pages+0xbab/0x4970 mm/userfaultfd.c:1583
userfaultfd_move fs/userfaultfd.c:2008 [inline]
userfaultfd_ioctl+0x5e1/0x60e0 fs/userfaultfd.c:2126
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:904 [inline]
__se_sys_ioctl fs/ioctl.c:890 [inline]
__x64_sys_ioctl+0x193/0x220 fs/ioctl.c:890
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xd2/0x260 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x6d/0x75
RIP: 0033:0x7fd48da20329
Code: 48 83 c4 28 c3 e8 37 17 00 00 0f 1f 80 00 00 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 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffd1244f8e8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007ffd1244fab8 RCX: 00007fd48da20329
RDX: 00000000200000c0 RSI: 00000000c028aa05 RDI: 0000000000000003
RBP: 00007fd48da93610 R08: 00007ffd1244fab8 R09: 00007ffd1244fab8
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000001
R13: 00007ffd1244faa8 R14: 0000000000000001 R15: 0000000000000001
</TASK>
---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at [email protected].
syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title
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.
If you want to overwrite report's subsystems, reply with:
#syz set subsystems: new-subsystem
(See the list of subsystem names on the web dashboard)
If the report is a duplicate of another one, reply with:
#syz dup: exact-subject-of-another-report
If you want to undo deduplication, reply with:
#syz undup
On 19.03.24 10:52, syzbot wrote:
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit: e5eb28f6d1af Merge tag 'mm-nonmm-stable-2024-03-14-09-36' ..
> git tree: upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=160dc26e180000
> kernel config: https://syzkaller.appspot.com/x/.config?x=4ffb854606e658d
> dashboard link: https://syzkaller.appspot.com/bug?extid=49056626fe41e01f2ba7
> compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=10f467b9180000
> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=173b7ac9180000
>
> Downloadable assets:
> disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/7bc7510fe41f/non_bootable_disk-e5eb28f6.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/a5c7ad05d6b2/vmlinux-e5eb28f6.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/531cb1917612/bzImage-e5eb28f6.xz
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: [email protected]
>
> ============================================
> WARNING: possible recursive locking detected
> 6.8.0-syzkaller-09791-ge5eb28f6d1af #0 Not tainted
> --------------------------------------------
> syz-executor258/5169 is trying to acquire lock:
> ffff88802a6d23d0 (&vma->vm_lock->lock){++++}-{3:3}, at: uffd_move_lock mm/userfaultfd.c:1447 [inline]
> ffff88802a6d23d0 (&vma->vm_lock->lock){++++}-{3:3}, at: move_pages+0xbab/0x4970 mm/userfaultfd.c:1583
>
> but task is already holding lock:
> ffff88802a6d2580 (&vma->vm_lock->lock){++++}-{3:3}, at: uffd_move_lock mm/userfaultfd.c:1445 [inline]
> ffff88802a6d2580 (&vma->vm_lock->lock){++++}-{3:3}, at: move_pages+0xb6f/0x4970 mm/userfaultfd.c:1583
>
> other info that might help us debug this:
> Possible unsafe locking scenario:
>
> CPU0
> ----
> lock(&vma->vm_lock->lock);
> lock(&vma->vm_lock->lock);
>
> *** DEADLOCK ***
>
> May be due to missing lock nesting notation
>
> 2 locks held by syz-executor258/5169:
> #0: ffff888015086a20 (&mm->mmap_lock){++++}-{3:3}, at: mmap_read_lock include/linux/mmap_lock.h:146 [inline]
> #0: ffff888015086a20 (&mm->mmap_lock){++++}-{3:3}, at: uffd_move_lock mm/userfaultfd.c:1438 [inline]
> #0: ffff888015086a20 (&mm->mmap_lock){++++}-{3:3}, at: move_pages+0x8df/0x4970 mm/userfaultfd.c:1583
> #1: ffff88802a6d2580 (&vma->vm_lock->lock){++++}-{3:3}, at: uffd_move_lock mm/userfaultfd.c:1445 [inline]
> #1: ffff88802a6d2580 (&vma->vm_lock->lock){++++}-{3:3}, at: move_pages+0xb6f/0x4970 mm/userfaultfd.c:1583
>
> stack backtrace:
> CPU: 2 PID: 5169 Comm: syz-executor258 Not tainted 6.8.0-syzkaller-09791-ge5eb28f6d1af #0
> Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
> Call Trace:
> <TASK>
> __dump_stack lib/dump_stack.c:88 [inline]
> dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:114
> check_deadlock kernel/locking/lockdep.c:3062 [inline]
> validate_chain kernel/locking/lockdep.c:3856 [inline]
> __lock_acquire+0x20e6/0x3b30 kernel/locking/lockdep.c:5137
> lock_acquire kernel/locking/lockdep.c:5754 [inline]
> lock_acquire+0x1b1/0x540 kernel/locking/lockdep.c:5719
> down_read+0x9a/0x330 kernel/locking/rwsem.c:1526
> uffd_move_lock mm/userfaultfd.c:1447 [inline]
> move_pages+0xbab/0x4970 mm/userfaultfd.c:1583
> userfaultfd_move fs/userfaultfd.c:2008 [inline]
> userfaultfd_ioctl+0x5e1/0x60e0 fs/userfaultfd.c:2126
> vfs_ioctl fs/ioctl.c:51 [inline]
> __do_sys_ioctl fs/ioctl.c:904 [inline]
> __se_sys_ioctl fs/ioctl.c:890 [inline]
> __x64_sys_ioctl+0x193/0x220 fs/ioctl.c:890
> do_syscall_x64 arch/x86/entry/common.c:52 [inline]
> do_syscall_64+0xd2/0x260 arch/x86/entry/common.c:83
> entry_SYSCALL_64_after_hwframe+0x6d/0x75
> RIP: 0033:0x7fd48da20329
> Code: 48 83 c4 28 c3 e8 37 17 00 00 0f 1f 80 00 00 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 b8 ff ff ff f7 d8 64 89 01 48
> RSP: 002b:00007ffd1244f8e8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
> RAX: ffffffffffffffda RBX: 00007ffd1244fab8 RCX: 00007fd48da20329
> RDX: 00000000200000c0 RSI: 00000000c028aa05 RDI: 0000000000000003
> RBP: 00007fd48da93610 R08: 00007ffd1244fab8 R09: 00007ffd1244fab8
> R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000001
> R13: 00007ffd1244faa8 R14: 0000000000000001 R15: 0000000000000001
> </TASK>
>
>
> ---
> This report is generated by a bot. It may contain errors.
> See https://goo.gl/tpsmEJ for more information about syzbot.
> syzbot engineers can be reached at [email protected].
>
> syzbot will keep track of this issue. See:
> https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
>
> If the report is already addressed, let syzbot know by replying with:
> #syz fix: exact-commit-title
>
> 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.
>
> If you want to overwrite report's subsystems, reply with:
> #syz set subsystems: new-subsystem
> (See the list of subsystem names on the web dashboard)
>
> If the report is a duplicate of another one, reply with:
> #syz dup: exact-subject-of-another-report
>
> If you want to undo deduplication, reply with:
> #syz undup
>
Possibly
commit 867a43a34ff8a38772212045262b2c9b77807ea3
Author: Lokesh Gidra <[email protected]>
Date: Thu Feb 15 10:27:56 2024 -0800
userfaultfd: use per-vma locks in userfaultfd operations
All userfaultfd operations, except write-protect, opportunistically use
per-vma locks to lock vmas. On failure, attempt again inside mmap_lock
critical section.
Write-protect operation requires mmap_lock as it iterates over multiple
vmas.
and
commit 5e4c24a57b0c126686534b5b159a406c5dd02400
Author: Lokesh Gidra <[email protected]>
Date: Thu Feb 15 10:27:54 2024 -0800
userfaultfd: protect mmap_changing with rw_sem in userfaulfd_ctx
Increments and loads to mmap_changing are always in mmap_lock critical
section. This ensures that if userspace requests event notification for
non-cooperative operations (e.g. mremap), userfaultfd operations don't
occur concurrently.
This can be achieved by using a separate read-write semaphore in
userfaultfd_ctx such that increments are done in write-mode and loads in
read-mode, thereby eliminating the dependency on mmap_lock for this
purpose.
This is a preparatory step before we replace mmap_lock usage with per-vma
locks in fill/move ioctls.
might responsible.
CCin Lokesh
--
Cheers,
David / dhildenb
On Tue, Mar 19, 2024 at 6:37 AM David Hildenbrand <[email protected]> wrote:
>
> On 19.03.24 10:52, syzbot wrote:
> > Hello,
> >
> > syzbot found the following issue on:
> >
> > HEAD commit: e5eb28f6d1af Merge tag 'mm-nonmm-stable-2024-03-14-09-36' ..
> > git tree: upstream
> > console output: https://syzkaller.appspot.com/x/log.txt?x=160dc26e180000
> > kernel config: https://syzkaller.appspot.com/x/.config?x=4ffb854606e658d
> > dashboard link: https://syzkaller.appspot.com/bug?extid=49056626fe41e01f2ba7
> > compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
> > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=10f467b9180000
> > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=173b7ac9180000
> >
> > Downloadable assets:
> > disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/7bc7510fe41f/non_bootable_disk-e5eb28f6.raw.xz
> > vmlinux: https://storage.googleapis.com/syzbot-assets/a5c7ad05d6b2/vmlinux-e5eb28f6.xz
> > kernel image: https://storage.googleapis.com/syzbot-assets/531cb1917612/bzImage-e5eb28f6.xz
> >
> > IMPORTANT: if you fix the issue, please add the following tag to the commit:
> > Reported-by: [email protected]
> >
> > ============================================
> > WARNING: possible recursive locking detected
> > 6.8.0-syzkaller-09791-ge5eb28f6d1af #0 Not tainted
> > --------------------------------------------
> > syz-executor258/5169 is trying to acquire lock:
> > ffff88802a6d23d0 (&vma->vm_lock->lock){++++}-{3:3}, at: uffd_move_lock mm/userfaultfd.c:1447 [inline]
> > ffff88802a6d23d0 (&vma->vm_lock->lock){++++}-{3:3}, at: move_pages+0xbab/0x4970 mm/userfaultfd.c:1583
> >
> > but task is already holding lock:
> > ffff88802a6d2580 (&vma->vm_lock->lock){++++}-{3:3}, at: uffd_move_lock mm/userfaultfd.c:1445 [inline]
> > ffff88802a6d2580 (&vma->vm_lock->lock){++++}-{3:3}, at: move_pages+0xb6f/0x4970 mm/userfaultfd.c:1583
> >
> > other info that might help us debug this:
> > Possible unsafe locking scenario:
> >
> > CPU0
> > ----
> > lock(&vma->vm_lock->lock);
> > lock(&vma->vm_lock->lock);
> >
> > *** DEADLOCK ***
> >
> > May be due to missing lock nesting notation
> >
> > 2 locks held by syz-executor258/5169:
> > #0: ffff888015086a20 (&mm->mmap_lock){++++}-{3:3}, at: mmap_read_lock include/linux/mmap_lock.h:146 [inline]
> > #0: ffff888015086a20 (&mm->mmap_lock){++++}-{3:3}, at: uffd_move_lock mm/userfaultfd.c:1438 [inline]
> > #0: ffff888015086a20 (&mm->mmap_lock){++++}-{3:3}, at: move_pages+0x8df/0x4970 mm/userfaultfd.c:1583
> > #1: ffff88802a6d2580 (&vma->vm_lock->lock){++++}-{3:3}, at: uffd_move_lock mm/userfaultfd.c:1445 [inline]
> > #1: ffff88802a6d2580 (&vma->vm_lock->lock){++++}-{3:3}, at: move_pages+0xb6f/0x4970 mm/userfaultfd.c:1583
> >
> > stack backtrace:
> > CPU: 2 PID: 5169 Comm: syz-executor258 Not tainted 6.8.0-syzkaller-09791-ge5eb28f6d1af #0
> > Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
> > Call Trace:
> > <TASK>
> > __dump_stack lib/dump_stack.c:88 [inline]
> > dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:114
> > check_deadlock kernel/locking/lockdep.c:3062 [inline]
> > validate_chain kernel/locking/lockdep.c:3856 [inline]
> > __lock_acquire+0x20e6/0x3b30 kernel/locking/lockdep.c:5137
> > lock_acquire kernel/locking/lockdep.c:5754 [inline]
> > lock_acquire+0x1b1/0x540 kernel/locking/lockdep.c:5719
> > down_read+0x9a/0x330 kernel/locking/rwsem.c:1526
> > uffd_move_lock mm/userfaultfd.c:1447 [inline]
> > move_pages+0xbab/0x4970 mm/userfaultfd.c:1583
> > userfaultfd_move fs/userfaultfd.c:2008 [inline]
> > userfaultfd_ioctl+0x5e1/0x60e0 fs/userfaultfd.c:2126
> > vfs_ioctl fs/ioctl.c:51 [inline]
> > __do_sys_ioctl fs/ioctl.c:904 [inline]
> > __se_sys_ioctl fs/ioctl.c:890 [inline]
> > __x64_sys_ioctl+0x193/0x220 fs/ioctl.c:890
> > do_syscall_x64 arch/x86/entry/common.c:52 [inline]
> > do_syscall_64+0xd2/0x260 arch/x86/entry/common.c:83
> > entry_SYSCALL_64_after_hwframe+0x6d/0x75
> > RIP: 0033:0x7fd48da20329
> > Code: 48 83 c4 28 c3 e8 37 17 00 00 0f 1f 80 00 00 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 b8 ff ff ff f7 d8 64 89 01 48
> > RSP: 002b:00007ffd1244f8e8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
> > RAX: ffffffffffffffda RBX: 00007ffd1244fab8 RCX: 00007fd48da20329
> > RDX: 00000000200000c0 RSI: 00000000c028aa05 RDI: 0000000000000003
> > RBP: 00007fd48da93610 R08: 00007ffd1244fab8 R09: 00007ffd1244fab8
> > R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000001
> > R13: 00007ffd1244faa8 R14: 0000000000000001 R15: 0000000000000001
> > </TASK>
> >
> >
> > ---
> > This report is generated by a bot. It may contain errors.
> > See https://goo.gl/tpsmEJ for more information about syzbot.
> > syzbot engineers can be reached at [email protected].
> >
> > syzbot will keep track of this issue. See:
> > https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
> >
> > If the report is already addressed, let syzbot know by replying with:
> > #syz fix: exact-commit-title
> >
> > 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.
> >
> > If you want to overwrite report's subsystems, reply with:
> > #syz set subsystems: new-subsystem
> > (See the list of subsystem names on the web dashboard)
> >
> > If the report is a duplicate of another one, reply with:
> > #syz dup: exact-subject-of-another-report
> >
> > If you want to undo deduplication, reply with:
> > #syz undup
> >
>
> Possibly
>
> commit 867a43a34ff8a38772212045262b2c9b77807ea3
> Author: Lokesh Gidra <[email protected]>
> Date: Thu Feb 15 10:27:56 2024 -0800
>
> userfaultfd: use per-vma locks in userfaultfd operations
>
> All userfaultfd operations, except write-protect, opportunistically use
> per-vma locks to lock vmas. On failure, attempt again inside mmap_lock
> critical section.
>
> Write-protect operation requires mmap_lock as it iterates over multiple
> vmas.
>
> and
>
> commit 5e4c24a57b0c126686534b5b159a406c5dd02400
> Author: Lokesh Gidra <[email protected]>
> Date: Thu Feb 15 10:27:54 2024 -0800
>
> userfaultfd: protect mmap_changing with rw_sem in userfaulfd_ctx
>
> Increments and loads to mmap_changing are always in mmap_lock critical
> section. This ensures that if userspace requests event notification for
> non-cooperative operations (e.g. mremap), userfaultfd operations don't
> occur concurrently.
>
> This can be achieved by using a separate read-write semaphore in
> userfaultfd_ctx such that increments are done in write-mode and loads in
> read-mode, thereby eliminating the dependency on mmap_lock for this
> purpose.
>
> This is a preparatory step before we replace mmap_lock usage with per-vma
> locks in fill/move ioctls.
>
> might responsible.
>
> CCin Lokesh
Thanks for looping me in. Taking a look.
>
> --
> Cheers,
>
> David / dhildenb
>
On Tue, Mar 19, 2024 at 10:24 AM Lokesh Gidra <[email protected]> wrote:
>
> On Tue, Mar 19, 2024 at 6:37 AM David Hildenbrand <[email protected]> wrote:
> >
> > On 19.03.24 10:52, syzbot wrote:
> > > Hello,
> > >
> > > syzbot found the following issue on:
> > >
> > > HEAD commit: e5eb28f6d1af Merge tag 'mm-nonmm-stable-2024-03-14-09-36' ..
> > > git tree: upstream
> > > console output: https://syzkaller.appspot.com/x/log.txt?x=160dc26e180000
> > > kernel config: https://syzkaller.appspot.com/x/.config?x=4ffb854606e658d
> > > dashboard link: https://syzkaller.appspot.com/bug?extid=49056626fe41e01f2ba7
> > > compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
> > > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=10f467b9180000
> > > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=173b7ac9180000
> > >
> > > Downloadable assets:
> > > disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/7bc7510fe41f/non_bootable_disk-e5eb28f6.raw.xz
> > > vmlinux: https://storage.googleapis.com/syzbot-assets/a5c7ad05d6b2/vmlinux-e5eb28f6.xz
> > > kernel image: https://storage.googleapis.com/syzbot-assets/531cb1917612/bzImage-e5eb28f6.xz
> > >
> > > IMPORTANT: if you fix the issue, please add the following tag to the commit:
> > > Reported-by: [email protected]
> > >
> > > ============================================
> > > WARNING: possible recursive locking detected
> > > 6.8.0-syzkaller-09791-ge5eb28f6d1af #0 Not tainted
> > > --------------------------------------------
> > > syz-executor258/5169 is trying to acquire lock:
> > > ffff88802a6d23d0 (&vma->vm_lock->lock){++++}-{3:3}, at: uffd_move_lock mm/userfaultfd.c:1447 [inline]
> > > ffff88802a6d23d0 (&vma->vm_lock->lock){++++}-{3:3}, at: move_pages+0xbab/0x4970 mm/userfaultfd.c:1583
> > >
> > > but task is already holding lock:
> > > ffff88802a6d2580 (&vma->vm_lock->lock){++++}-{3:3}, at: uffd_move_lock mm/userfaultfd.c:1445 [inline]
> > > ffff88802a6d2580 (&vma->vm_lock->lock){++++}-{3:3}, at: move_pages+0xb6f/0x4970 mm/userfaultfd.c:1583
> > >
> > > other info that might help us debug this:
> > > Possible unsafe locking scenario:
> > >
> > > CPU0
> > > ----
> > > lock(&vma->vm_lock->lock);
> > > lock(&vma->vm_lock->lock);
> > >
> > > *** DEADLOCK ***
> > >
> > > May be due to missing lock nesting notation
> > >
> > > 2 locks held by syz-executor258/5169:
> > > #0: ffff888015086a20 (&mm->mmap_lock){++++}-{3:3}, at: mmap_read_lock include/linux/mmap_lock.h:146 [inline]
> > > #0: ffff888015086a20 (&mm->mmap_lock){++++}-{3:3}, at: uffd_move_lock mm/userfaultfd.c:1438 [inline]
> > > #0: ffff888015086a20 (&mm->mmap_lock){++++}-{3:3}, at: move_pages+0x8df/0x4970 mm/userfaultfd.c:1583
> > > #1: ffff88802a6d2580 (&vma->vm_lock->lock){++++}-{3:3}, at: uffd_move_lock mm/userfaultfd.c:1445 [inline]
> > > #1: ffff88802a6d2580 (&vma->vm_lock->lock){++++}-{3:3}, at: move_pages+0xb6f/0x4970 mm/userfaultfd.c:1583
> > >
> > > stack backtrace:
> > > CPU: 2 PID: 5169 Comm: syz-executor258 Not tainted 6.8.0-syzkaller-09791-ge5eb28f6d1af #0
> > > Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
> > > Call Trace:
> > > <TASK>
> > > __dump_stack lib/dump_stack.c:88 [inline]
> > > dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:114
> > > check_deadlock kernel/locking/lockdep.c:3062 [inline]
> > > validate_chain kernel/locking/lockdep.c:3856 [inline]
> > > __lock_acquire+0x20e6/0x3b30 kernel/locking/lockdep.c:5137
> > > lock_acquire kernel/locking/lockdep.c:5754 [inline]
> > > lock_acquire+0x1b1/0x540 kernel/locking/lockdep.c:5719
> > > down_read+0x9a/0x330 kernel/locking/rwsem.c:1526
> > > uffd_move_lock mm/userfaultfd.c:1447 [inline]
> > > move_pages+0xbab/0x4970 mm/userfaultfd.c:1583
> > > userfaultfd_move fs/userfaultfd.c:2008 [inline]
> > > userfaultfd_ioctl+0x5e1/0x60e0 fs/userfaultfd.c:2126
> > > vfs_ioctl fs/ioctl.c:51 [inline]
> > > __do_sys_ioctl fs/ioctl.c:904 [inline]
> > > __se_sys_ioctl fs/ioctl.c:890 [inline]
> > > __x64_sys_ioctl+0x193/0x220 fs/ioctl.c:890
> > > do_syscall_x64 arch/x86/entry/common.c:52 [inline]
> > > do_syscall_64+0xd2/0x260 arch/x86/entry/common.c:83
> > > entry_SYSCALL_64_after_hwframe+0x6d/0x75
> > > RIP: 0033:0x7fd48da20329
> > > Code: 48 83 c4 28 c3 e8 37 17 00 00 0f 1f 80 00 00 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 b8 ff ff ff f7 d8 64 89 01 48
> > > RSP: 002b:00007ffd1244f8e8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
> > > RAX: ffffffffffffffda RBX: 00007ffd1244fab8 RCX: 00007fd48da20329
> > > RDX: 00000000200000c0 RSI: 00000000c028aa05 RDI: 0000000000000003
> > > RBP: 00007fd48da93610 R08: 00007ffd1244fab8 R09: 00007ffd1244fab8
> > > R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000001
> > > R13: 00007ffd1244faa8 R14: 0000000000000001 R15: 0000000000000001
> > > </TASK>
> > >
> > >
> > > ---
> > > This report is generated by a bot. It may contain errors.
> > > See https://goo.gl/tpsmEJ for more information about syzbot.
> > > syzbot engineers can be reached at [email protected].
> > >
> > > syzbot will keep track of this issue. See:
> > > https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
> > >
> > > If the report is already addressed, let syzbot know by replying with:
> > > #syz fix: exact-commit-title
> > >
> > > 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.
> > >
> > > If you want to overwrite report's subsystems, reply with:
> > > #syz set subsystems: new-subsystem
> > > (See the list of subsystem names on the web dashboard)
> > >
> > > If the report is a duplicate of another one, reply with:
> > > #syz dup: exact-subject-of-another-report
> > >
> > > If you want to undo deduplication, reply with:
> > > #syz undup
> > >
> >
> > Possibly
> >
> > commit 867a43a34ff8a38772212045262b2c9b77807ea3
> > Author: Lokesh Gidra <[email protected]>
> > Date: Thu Feb 15 10:27:56 2024 -0800
> >
> > userfaultfd: use per-vma locks in userfaultfd operations
> >
> > All userfaultfd operations, except write-protect, opportunistically use
> > per-vma locks to lock vmas. On failure, attempt again inside mmap_lock
> > critical section.
> >
> > Write-protect operation requires mmap_lock as it iterates over multiple
> > vmas.
> >
> > and
> >
> > commit 5e4c24a57b0c126686534b5b159a406c5dd02400
> > Author: Lokesh Gidra <[email protected]>
> > Date: Thu Feb 15 10:27:54 2024 -0800
> >
> > userfaultfd: protect mmap_changing with rw_sem in userfaulfd_ctx
> >
> > Increments and loads to mmap_changing are always in mmap_lock critical
> > section. This ensures that if userspace requests event notification for
> > non-cooperative operations (e.g. mremap), userfaultfd operations don't
> > occur concurrently.
> >
> > This can be achieved by using a separate read-write semaphore in
> > userfaultfd_ctx such that increments are done in write-mode and loads in
> > read-mode, thereby eliminating the dependency on mmap_lock for this
> > purpose.
> >
> > This is a preparatory step before we replace mmap_lock usage with per-vma
> > locks in fill/move ioctls.
> >
> > might responsible.
> >
I tried reproducing the issue with the provided reproducer locally and
with few additional checks:
down_read(&(*dst_vmap)->vm_lock->lock);
if (*dst_vmap != *src_vmap) {
BUG_ON((*src_vmap)->vm_lock == (*dst_vmap)->vm_lock);
BUG_ON(&(*src_vmap)->vm_lock->lock == &(*dst_vmap)->vm_lock->lock);
BUG_ON(rwsem_is_locked(&(*src_vmap)->vm_lock->lock));
down_read(&(*src_vmap)->vm_lock->lock);
}
None of the BUG_ONs are causing pani but the following down_read() is
reporting the deadlock as above. Even if I change the if condition to
if (&(*dst_vmap)->vm_lock->lock != &(*src_vmap)->vm_lock->lock)
I still get the deadlock trace. Possibly a bug in lockdep?
> > CCin Lokesh
>
> Thanks for looping me in. Taking a look.
> >
> > --
> > Cheers,
> >
> > David / dhildenb
> >
On Tue, 19 Mar 2024 02:52:16 -0700
> syzbot found the following issue on:
>
> HEAD commit: e5eb28f6d1af Merge tag 'mm-nonmm-stable-2024-03-14-09-36' ..
> git tree: upstream
> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=173b7ac9180000
#syz test https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git e5eb28f6d1af
--- x/mm/userfaultfd.c
+++ y/mm/userfaultfd.c
@@ -1442,9 +1442,9 @@ static int uffd_move_lock(struct mm_stru
* See comment in lock_vma() as to why not using
* vma_start_read() here.
*/
- down_read(&(*dst_vmap)->vm_lock->lock);
+ down_read_nested(&(*dst_vmap)->vm_lock->lock, 1);
if (*dst_vmap != *src_vmap)
- down_read(&(*src_vmap)->vm_lock->lock);
+ down_read_nested(&(*src_vmap)->vm_lock->lock, 2);
}
mmap_read_unlock(mm);
return err;
--
Hello,
syzbot has tested the proposed patch and the reproducer did not trigger any issue:
Reported-and-tested-by: [email protected]
Tested on:
commit: e5eb28f6 Merge tag 'mm-nonmm-stable-2024-03-14-09-36' ..
git tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
console output: https://syzkaller.appspot.com/x/log.txt?x=10b7afc1180000
kernel config: https://syzkaller.appspot.com/x/.config?x=4ffb854606e658d
dashboard link: https://syzkaller.appspot.com/bug?extid=49056626fe41e01f2ba7
compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
patch: https://syzkaller.appspot.com/x/patch.diff?x=17d44231180000
Note: testing is done by a robot and is best-effort only.