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AJvYcCUfNalsyaflYkTjQqAVgoqQOuknrjsCZZevbZcxV+XghUg17kl2koruCceFNJOojqWj3vSK5nGQWssSX74KpxgWork= X-Gm-Message-State: AOJu0Yy+XdLjBIixCzGN0ofLjX+XL3pkGery5L/2F0fIJ4L9MitJ4IMH 9Q8aC50MEcgcymmfgngNGj/21kRz6BTIj/JNccoL5l8Ip3mhKKV3ImoVivowW9vwRCmCUZ2I8Sd kucZP07vIc2XtmHNCZxCe7cSlWsJTWQA+ZEoU X-Google-Smtp-Source: AGHT+IFo2TtSZPZuLnkj1tMjvn6g7EnzYXBWTOsR07hm4EyRVhgBVnitCvPmxvFvhbbg8S2ZupVM/Q6pqVNqiyIzEHw= X-Received: by 2002:ac2:4903:0:b0:513:cf12:2db3 with SMTP id n3-20020ac24903000000b00513cf122db3mr2103895lfi.61.1710869073113; Tue, 19 Mar 2024 10:24:33 -0700 (PDT) MIME-Version: 1.0 References: <000000000000e97f090614006d76@google.com> In-Reply-To: From: Lokesh Gidra Date: Tue, 19 Mar 2024 10:24:20 -0700 Message-ID: Subject: Re: [syzbot] [mm?] possible deadlock in move_pages To: David Hildenbrand Cc: syzbot , akpm@linux-foundation.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, syzkaller-bugs@googlegroups.com, Suren Baghdasaryan Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 62A0240003 X-Stat-Signature: uae78n1ran981upzen8hhwrahqjx187c X-Rspam-User: X-HE-Tag: 1710869075-502380 X-HE-Meta: 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 h28Z0y3i Bb2Pyy+SssViIgx2nVc8wH7Juabf+NRvJibfoCuY94bQQ7QBBOeFe1NwJeRcD+br1pPrOT6G24ZSlED7jmtVc9eRDyRYKH1vdxg4cmBPTdKxl9rKdy3zenVFbXVPYDGeKOldJgE8o/PaUeWXWUOJw3nWxZHiwsqan1mnXGvPiXULGbnoRAhlc+FhPf5C7LojmvG9DzPcRwPxu6Mj4vyPrnq+Oig2pQGU2O+FkI8DQSz1edfvCrNrZShVY5l0rH6hCCliDnIzJ+E8mqNmy7/ej4HslXi8/DRvOpE/ZzuMsDYOphKiouxSt/JmU+2NaAqWhnnBO3Kt4rfq5ZyJBFJRNDzYv5Q== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, Mar 19, 2024 at 6:37=E2=80=AFAM David Hildenbrand wrote: > > On 19.03.24 10:52, syzbot wrote: > > Hello, > > > > syzbot found the following issue on: > > > > HEAD commit: e5eb28f6d1af Merge tag 'mm-nonmm-stable-2024-03-14-09-3= 6' .. > > git tree: upstream > > console output: https://syzkaller.appspot.com/x/log.txt?x=3D160dc26e180= 000 > > kernel config: https://syzkaller.appspot.com/x/.config?x=3D4ffb854606e= 658d > > dashboard link: https://syzkaller.appspot.com/bug?extid=3D49056626fe41e= 01f2ba7 > > 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=3D10f467b91= 80000 > > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=3D173b7ac9180= 000 > > > > 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/vmli= nux-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 co= mmit: > > Reported-by: syzbot+49056626fe41e01f2ba7@syzkaller.appspotmail.com > > > > =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D > > 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+0xba= b/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+0xb6= f/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+0x8= df/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_page= s+0xb6f/0x4970 mm/userfaultfd.c:1583 > > > > stack backtrace: > > CPU: 2 PID: 5169 Comm: syz-executor258 Not tainted 6.8.0-syzkaller-0979= 1-ge5eb28f6d1af #0 > > Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-= 1.16.2-1 04/01/2014 > > Call Trace: > > > > __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 > > > > > > > > --- > > 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 syzkaller@googlegroups.com. > > > > 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 > 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_l= ock > critical section. > > Write-protect operation requires mmap_lock as it iterates over multi= ple > vmas. > > and > > commit 5e4c24a57b0c126686534b5b159a406c5dd02400 > Author: Lokesh Gidra > 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 critic= al > section. This ensures that if userspace requests event notification= for > non-cooperative operations (e.g. mremap), userfaultfd operations do= n'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 load= s 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 pe= r-vma > locks in fill/move ioctls. > > might responsible. > > CCin Lokesh Thanks for looping me in. Taking a look. > > -- > Cheers, > > David / dhildenb >