From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-f49.google.com (mail-wm0-f49.google.com [74.125.82.49]) by kanga.kvack.org (Postfix) with ESMTP id ACA02828DE for ; Fri, 8 Jan 2016 11:58:54 -0500 (EST) Received: by mail-wm0-f49.google.com with SMTP id f206so143393924wmf.0 for ; Fri, 08 Jan 2016 08:58:54 -0800 (PST) Received: from mail-wm0-x235.google.com (mail-wm0-x235.google.com. [2a00:1450:400c:c09::235]) by mx.google.com with ESMTPS id ln5si24118017wjb.38.2016.01.08.08.58.53 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 08 Jan 2016 08:58:53 -0800 (PST) Received: by mail-wm0-x235.google.com with SMTP id f206so142382845wmf.0 for ; Fri, 08 Jan 2016 08:58:53 -0800 (PST) MIME-Version: 1.0 From: Dmitry Vyukov Date: Fri, 8 Jan 2016 17:58:33 +0100 Message-ID: Subject: mm: possible deadlock in mm_take_all_locks Content-Type: text/plain; charset=UTF-8 Sender: owner-linux-mm@kvack.org List-ID: To: Peter Zijlstra , Ingo Molnar , LKML , Andrew Morton , "Kirill A. Shutemov" , Oleg Nesterov , Chen Gang , "linux-mm@kvack.org" Cc: syzkaller , Kostya Serebryany , Alexander Potapenko , Eric Dumazet , Sasha Levin Hello, I've hit the following deadlock warning while running syzkaller fuzzer on commit b06f3a168cdcd80026276898fd1fee443ef25743. As far as I understand this is a false positive, because both call stacks are protected by mm_all_locks_mutex. What would be a way to annotate such locking discipline? ====================================================== [ INFO: possible circular locking dependency detected ] 4.4.0-rc8+ #211 Not tainted ------------------------------------------------------- syz-executor/11520 is trying to acquire lock: (&mapping->i_mmap_rwsem){++++..}, at: [< inline >] vm_lock_mapping mm/mmap.c:3159 (&mapping->i_mmap_rwsem){++++..}, at: [] mm_take_all_locks+0x1bd/0x5f0 mm/mmap.c:3207 but task is already holding lock: (&hugetlbfs_i_mmap_rwsem_key){+.+...}, at: [< inline >] vm_lock_mapping mm/mmap.c:3159 (&hugetlbfs_i_mmap_rwsem_key){+.+...}, at: [] mm_take_all_locks+0x1bd/0x5f0 mm/mmap.c:3207 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #1 (&hugetlbfs_i_mmap_rwsem_key){+.+...}: [] lock_acquire+0x1dc/0x430 kernel/locking/lockdep.c:3585 [] _down_write_nest_lock+0x49/0xa0 kernel/locking/rwsem.c:129 [< inline >] vm_lock_mapping mm/mmap.c:3159 [] mm_take_all_locks+0x1bd/0x5f0 mm/mmap.c:3207 [] do_mmu_notifier_register+0x328/0x420 mm/mmu_notifier.c:267 [] mmu_notifier_register+0x22/0x30 mm/mmu_notifier.c:317 [< inline >] kvm_init_mmu_notifier arch/x86/kvm/../../../virt/kvm/kvm_main.c:474 [< inline >] kvm_create_vm arch/x86/kvm/../../../virt/kvm/kvm_main.c:592 [< inline >] kvm_dev_ioctl_create_vm arch/x86/kvm/../../../virt/kvm/kvm_main.c:2966 [] kvm_dev_ioctl+0x72a/0x920 arch/x86/kvm/../../../virt/kvm/kvm_main.c:2995 [< inline >] vfs_ioctl fs/ioctl.c:43 [] do_vfs_ioctl+0x681/0xe40 fs/ioctl.c:607 [< inline >] SYSC_ioctl fs/ioctl.c:622 [] SyS_ioctl+0x8f/0xc0 fs/ioctl.c:613 [] entry_SYSCALL_64_fastpath+0x16/0x7a arch/x86/entry/entry_64.S:185 -> #0 (&mapping->i_mmap_rwsem){++++..}: [< inline >] check_prev_add kernel/locking/lockdep.c:1853 [< inline >] check_prevs_add kernel/locking/lockdep.c:1958 [< inline >] validate_chain kernel/locking/lockdep.c:2144 [] __lock_acquire+0x320d/0x4720 kernel/locking/lockdep.c:3206 [< inline >] __lock_release kernel/locking/lockdep.c:3432 [] lock_release+0x697/0xce0 kernel/locking/lockdep.c:3604 [] up_write+0x1a/0x60 kernel/locking/rwsem.c:91 [< inline >] i_mmap_unlock_write include/linux/fs.h:504 [< inline >] vm_unlock_mapping mm/mmap.c:3254 [] mm_drop_all_locks+0x266/0x320 mm/mmap.c:3278 [] do_mmu_notifier_register+0x286/0x420 mm/mmu_notifier.c:292 [] mmu_notifier_register+0x22/0x30 mm/mmu_notifier.c:317 [< inline >] kvm_init_mmu_notifier arch/x86/kvm/../../../virt/kvm/kvm_main.c:474 [< inline >] kvm_create_vm arch/x86/kvm/../../../virt/kvm/kvm_main.c:592 [< inline >] kvm_dev_ioctl_create_vm arch/x86/kvm/../../../virt/kvm/kvm_main.c:2966 [] kvm_dev_ioctl+0x72a/0x920 arch/x86/kvm/../../../virt/kvm/kvm_main.c:2995 [< inline >] vfs_ioctl fs/ioctl.c:43 [] do_vfs_ioctl+0x681/0xe40 fs/ioctl.c:607 [< inline >] SYSC_ioctl fs/ioctl.c:622 [] SyS_ioctl+0x8f/0xc0 fs/ioctl.c:613 [] entry_SYSCALL_64_fastpath+0x16/0x7a arch/x86/entry/entry_64.S:185 other info that might help us debug this: Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&hugetlbfs_i_mmap_rwsem_key); lock(&mapping->i_mmap_rwsem); lock(&hugetlbfs_i_mmap_rwsem_key); lock(&mapping->i_mmap_rwsem); *** DEADLOCK *** 3 locks held by syz-executor/11520: #0: (&mm->mmap_sem){++++++}, at: [] do_mmu_notifier_register+0x320/0x420 mm/mmu_notifier.c:266 #1: (mm_all_locks_mutex){+.+...}, at: [] mm_take_all_locks+0x47/0x5f0 mm/mmap.c:3201 #2: (&hugetlbfs_i_mmap_rwsem_key){+.+...}, at: [< inline >] vm_lock_mapping mm/mmap.c:3159 #2: (&hugetlbfs_i_mmap_rwsem_key){+.+...}, at: [] mm_take_all_locks+0x1bd/0x5f0 mm/mmap.c:3207 stack backtrace: CPU: 2 PID: 11520 Comm: syz-executor Not tainted 4.4.0-rc8+ #211 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011 00000000ffffffff ffff88003613fa10 ffffffff82907ccd ffffffff88911190 ffffffff88911190 ffffffff889321c0 ffff88003613fa60 ffffffff8143cb68 ffff880034bbaf00 ffff880034bbb73a 0000000000000000 ffff880034bbb718 Call Trace: [< inline >] __dump_stack lib/dump_stack.c:15 [] dump_stack+0x6f/0xa2 lib/dump_stack.c:50 [] print_circular_bug+0x288/0x340 kernel/locking/lockdep.c:1226 [< inline >] check_prev_add kernel/locking/lockdep.c:1853 [< inline >] check_prevs_add kernel/locking/lockdep.c:1958 [< inline >] validate_chain kernel/locking/lockdep.c:2144 [] __lock_acquire+0x320d/0x4720 kernel/locking/lockdep.c:3206 [< inline >] __lock_release kernel/locking/lockdep.c:3432 [] lock_release+0x697/0xce0 kernel/locking/lockdep.c:3604 [] up_write+0x1a/0x60 kernel/locking/rwsem.c:91 [< inline >] i_mmap_unlock_write include/linux/fs.h:504 [< inline >] vm_unlock_mapping mm/mmap.c:3254 [] mm_drop_all_locks+0x266/0x320 mm/mmap.c:3278 [] do_mmu_notifier_register+0x286/0x420 mm/mmu_notifier.c:292 [] mmu_notifier_register+0x22/0x30 mm/mmu_notifier.c:317 [< inline >] kvm_init_mmu_notifier arch/x86/kvm/../../../virt/kvm/kvm_main.c:474 [< inline >] kvm_create_vm arch/x86/kvm/../../../virt/kvm/kvm_main.c:592 [< inline >] kvm_dev_ioctl_create_vm arch/x86/kvm/../../../virt/kvm/kvm_main.c:2966 [] kvm_dev_ioctl+0x72a/0x920 arch/x86/kvm/../../../virt/kvm/kvm_main.c:2995 [< inline >] vfs_ioctl fs/ioctl.c:43 [] do_vfs_ioctl+0x681/0xe40 fs/ioctl.c:607 [< inline >] SYSC_ioctl fs/ioctl.c:622 [] SyS_ioctl+0x8f/0xc0 fs/ioctl.c:613 [] entry_SYSCALL_64_fastpath+0x16/0x7a arch/x86/entry/entry_64.S:185 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org