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Date:   Thu, 16 Apr 2020 17:24:17 -0700 (PDT)
From:   Hugh Dickins <hughd@google.com>
To:     syzbot <syzbot+40b71e145e73f78f81ad@syzkaller.appspotmail.com>
cc:     Andrew Morton <akpm@linux-foundation.org>,
        Yang Shi <yang.shi@linux.alibaba.com>,
        Hugh Dickins <hughd@google.com>, linux-kernel@vger.kernel.org,
        linux-mm@kvack.org, syzkaller-bugs@googlegroups.com
Subject: Re: possible deadlock in user_shm_lock
In-Reply-To: <0000000000003712b305a331d3b1@google.com>
Message-ID: <alpine.LSU.2.11.2004161720350.16488@eggly.anvils>
References: <0000000000003712b305a331d3b1@google.com>
User-Agent: Alpine 2.11 (LSU 23 2013-08-11)
MIME-Version: 1.0
Content-Type: TEXT/PLAIN; charset=US-ASCII
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Mon, 13 Apr 2020, syzbot wrote:

> Hello,
> 
> syzbot found the following crash on:
> 
> HEAD commit:    ab6f762f printk: queue wake_up_klogd irq_work only if per-..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=17b90b2be00000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=23c5a352e32a1944
> dashboard link: https://syzkaller.appspot.com/bug?extid=40b71e145e73f78f81ad
> compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
> 
> Unfortunately, I don't have any reproducer for this crash yet.
> 
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+40b71e145e73f78f81ad@syzkaller.appspotmail.com
> 
> ========================================================
> WARNING: possible irq lock inversion dependency detected
> 5.6.0-syzkaller #0 Not tainted
> --------------------------------------------------------
> syz-executor.0/28978 just changed the state of lock:
> ffffffff89a5ee98 (shmlock_user_lock){+.+.}-{2:2}, at: spin_lock include/linux/spinlock.h:353 [inline]
> ffffffff89a5ee98 (shmlock_user_lock){+.+.}-{2:2}, at: user_shm_lock+0xab/0x230 mm/mlock.c:855
> but this lock was taken by another, SOFTIRQ-safe lock in the past:
>  (&xa->xa_lock#4){..-.}-{2:2}
> 
> 
> and interrupts could create inverse lock ordering between them.
> 
> 
> other info that might help us debug this:
> Chain exists of:
>   &xa->xa_lock#4 --> &info->lock --> shmlock_user_lock
> 
>  Possible interrupt unsafe locking scenario:
> 
>        CPU0                    CPU1
>        ----                    ----
>   lock(shmlock_user_lock);
>                                local_irq_disable();
>                                lock(&xa->xa_lock#4);
>                                lock(&info->lock);
>   <Interrupt>
>     lock(&xa->xa_lock#4);
> 
>  *** DEADLOCK ***
> 
> 1 lock held by syz-executor.0/28978:
>  #0: ffff88809ab12550 (&ids->rwsem){++++}-{3:3}, at: ipcget_new ipc/util.c:343 [inline]
>  #0: ffff88809ab12550 (&ids->rwsem){++++}-{3:3}, at: ipcget+0xc6/0xcb0 ipc/util.c:643
> 
> the shortest dependencies between 2nd lock and 1st lock:
>   -> (&xa->xa_lock#4){..-.}-{2:2} {
>      IN-SOFTIRQ-W at:
>                         lock_acquire+0x1f2/0x8f0 kernel/locking/lockdep.c:4923
>                         __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
>                         _raw_spin_lock_irqsave+0x8c/0xbf kernel/locking/spinlock.c:159
>                         test_clear_page_writeback+0x1d7/0x11e0 mm/page-writeback.c:2728
>                         end_page_writeback+0x239/0x520 mm/filemap.c:1317
>                         end_buffer_async_write+0x442/0x5c0 fs/buffer.c:384
>                         end_bio_bh_io_sync+0xe2/0x140 fs/buffer.c:3012
>                         bio_endio+0x473/0x820 block/bio.c:1422
>                         req_bio_endio block/blk-core.c:245 [inline]
>                         blk_update_request+0x3e1/0xdc0 block/blk-core.c:1472
>                         scsi_end_request+0x80/0x7b0 drivers/scsi/scsi_lib.c:575
>                         scsi_io_completion+0x1e7/0x1300 drivers/scsi/scsi_lib.c:959
>                         scsi_softirq_done+0x31e/0x3b0 drivers/scsi/scsi_lib.c:1454
>                         blk_done_softirq+0x2db/0x440 block/blk-softirq.c:37
>                         __do_softirq+0x26c/0x9f7 kernel/softirq.c:292
>                         invoke_softirq kernel/softirq.c:373 [inline]
>                         irq_exit+0x192/0x1d0 kernel/softirq.c:413
>                         exiting_irq arch/x86/include/asm/apic.h:546 [inline]
>                         do_IRQ+0xda/0x270 arch/x86/kernel/irq.c:263
>                         ret_from_intr+0x0/0x2b
>                         arch_local_irq_enable arch/x86/include/asm/paravirt.h:769 [inline]
>                         __raw_spin_unlock_irq include/linux/spinlock_api_smp.h:168 [inline]
>                         _raw_spin_unlock_irq+0x4b/0x80 kernel/locking/spinlock.c:199
>                         do_exit+0x57b/0x2dd0 kernel/exit.c:774
>                         call_usermodehelper_exec_async+0x507/0x710 kernel/umh.c:125
>                         ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352
>      INITIAL USE at:
>                        lock_acquire+0x1f2/0x8f0 kernel/locking/lockdep.c:4923
>                        __raw_spin_lock_irq include/linux/spinlock_api_smp.h:128 [inline]
>                        _raw_spin_lock_irq+0x5b/0x80 kernel/locking/spinlock.c:167
>                        spin_lock_irq include/linux/spinlock.h:378 [inline]
>                        __add_to_page_cache_locked+0x607/0xe00 mm/filemap.c:855
>                        add_to_page_cache_lru+0x1aa/0x700 mm/filemap.c:921
>                        do_read_cache_page+0x9ab/0x1810 mm/filemap.c:2755
>                        read_mapping_page include/linux/pagemap.h:397 [inline]
>                        read_part_sector+0xf6/0x600 block/partitions/core.c:643
>                        adfspart_check_ICS+0x9d/0xc80 block/partitions/acorn.c:360
>                        check_partition block/partitions/core.c:140 [inline]
>                        blk_add_partitions+0x474/0xe50 block/partitions/core.c:571
>                        bdev_disk_changed+0x1fb/0x380 fs/block_dev.c:1544
>                        __blkdev_get+0xb15/0x1530 fs/block_dev.c:1647
>                        blkdev_get+0x41/0x2b0 fs/block_dev.c:1749
>                        register_disk block/genhd.c:763 [inline]
>                        __device_add_disk+0xa4f/0x1170 block/genhd.c:853
>                        add_disk include/linux/genhd.h:294 [inline]
>                        brd_init+0x297/0x463 drivers/block/brd.c:533
>                        do_one_initcall+0x10a/0x7d0 init/main.c:1157
>                        do_initcall_level init/main.c:1230 [inline]
>                        do_initcalls init/main.c:1246 [inline]
>                        do_basic_setup init/main.c:1266 [inline]
>                        kernel_init_freeable+0x501/0x5ae init/main.c:1450
>                        kernel_init+0xd/0x1bb init/main.c:1357
>                        ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352
>    }
>    ... key      at: [<ffffffff8c681e60>] __key.18009+0x0/0x40
>    ... acquired at:
>    __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
>    _raw_spin_lock_irqsave+0x8c/0xbf kernel/locking/spinlock.c:159
>    shmem_uncharge+0x24/0x270 mm/shmem.c:341
>    __split_huge_page mm/huge_memory.c:2613 [inline]
>    split_huge_page_to_list+0x274b/0x33b0 mm/huge_memory.c:2886
>    split_huge_page include/linux/huge_mm.h:204 [inline]
>    shmem_punch_compound+0x13e/0x1e0 mm/shmem.c:814
>    shmem_undo_range+0x5f1/0x1b80 mm/shmem.c:870
>    shmem_truncate_range+0x27/0xa0 mm/shmem.c:980
>    shmem_setattr+0x8b6/0xc80 mm/shmem.c:1039
>    notify_change+0xb6d/0x1020 fs/attr.c:336
>    do_truncate+0x134/0x1f0 fs/open.c:64
>    do_sys_ftruncate+0x4a5/0x570 fs/open.c:195
>    do_syscall_64+0xf6/0x7d0 arch/x86/entry/common.c:295
>    entry_SYSCALL_64_after_hwframe+0x49/0xb3
> 
>  -> (&info->lock){....}-{2:2} {
>     INITIAL USE at:
>                      lock_acquire+0x1f2/0x8f0 kernel/locking/lockdep.c:4923
>                      __raw_spin_lock_irq include/linux/spinlock_api_smp.h:128 [inline]
>                      _raw_spin_lock_irq+0x5b/0x80 kernel/locking/spinlock.c:167
>                      spin_lock_irq include/linux/spinlock.h:378 [inline]
>                      shmem_getpage_gfp+0x937/0x2a10 mm/shmem.c:1882
>                      shmem_getpage mm/shmem.c:154 [inline]
>                      shmem_write_begin+0x102/0x1e0 mm/shmem.c:2483
>                      generic_perform_write+0x20a/0x4e0 mm/filemap.c:3302
>                      __generic_file_write_iter+0x24c/0x610 mm/filemap.c:3431
>                      generic_file_write_iter+0x3f3/0x630 mm/filemap.c:3463
>                      call_write_iter include/linux/fs.h:1907 [inline]
>                      new_sync_write+0x4a2/0x700 fs/read_write.c:484
>                      __vfs_write+0xc9/0x100 fs/read_write.c:497
>                      vfs_write+0x268/0x5d0 fs/read_write.c:559
>                      ksys_write+0x12d/0x250 fs/read_write.c:612
>                      do_syscall_64+0xf6/0x7d0 arch/x86/entry/common.c:295
>                      entry_SYSCALL_64_after_hwframe+0x49/0xb3
>   }
>   ... key      at: [<ffffffff8c66eb00>] __key.56434+0x0/0x40
>   ... acquired at:
>    __raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline]
>    _raw_spin_lock+0x2a/0x40 kernel/locking/spinlock.c:151
>    spin_lock include/linux/spinlock.h:353 [inline]
>    user_shm_lock+0xab/0x230 mm/mlock.c:855
>    shmem_lock+0x1dd/0x2d0 mm/shmem.c:2184
>    shmctl_do_lock+0x73f/0x8f0 ipc/shm.c:1111
>    ksys_shmctl.constprop.0+0x203/0x350 ipc/shm.c:1188
>    do_syscall_64+0xf6/0x7d0 arch/x86/entry/common.c:295
>    entry_SYSCALL_64_after_hwframe+0x49/0xb3
> 
> -> (shmlock_user_lock){+.+.}-{2:2} {
>    HARDIRQ-ON-W at:
>                     lock_acquire+0x1f2/0x8f0 kernel/locking/lockdep.c:4923
>                     __raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline]
>                     _raw_spin_lock+0x2a/0x40 kernel/locking/spinlock.c:151
>                     spin_lock include/linux/spinlock.h:353 [inline]
>                     user_shm_lock+0xab/0x230 mm/mlock.c:855
>                     hugetlb_file_setup+0x4e1/0x677 fs/hugetlbfs/inode.c:1416
>                     newseg+0x460/0xe60 ipc/shm.c:652
>                     ipcget_new ipc/util.c:344 [inline]
>                     ipcget+0xf0/0xcb0 ipc/util.c:643
>                     ksys_shmget ipc/shm.c:742 [inline]
>                     __do_sys_shmget ipc/shm.c:747 [inline]
>                     __se_sys_shmget ipc/shm.c:745 [inline]
>                     __x64_sys_shmget+0x139/0x1a0 ipc/shm.c:745
>                     do_syscall_64+0xf6/0x7d0 arch/x86/entry/common.c:295
>                     entry_SYSCALL_64_after_hwframe+0x49/0xb3
>    SOFTIRQ-ON-W at:
>                     lock_acquire+0x1f2/0x8f0 kernel/locking/lockdep.c:4923
>                     __raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline]
>                     _raw_spin_lock+0x2a/0x40 kernel/locking/spinlock.c:151
>                     spin_lock include/linux/spinlock.h:353 [inline]
>                     user_shm_lock+0xab/0x230 mm/mlock.c:855
>                     hugetlb_file_setup+0x4e1/0x677 fs/hugetlbfs/inode.c:1416
>                     newseg+0x460/0xe60 ipc/shm.c:652
>                     ipcget_new ipc/util.c:344 [inline]
>                     ipcget+0xf0/0xcb0 ipc/util.c:643
>                     ksys_shmget ipc/shm.c:742 [inline]
>                     __do_sys_shmget ipc/shm.c:747 [inline]
>                     __se_sys_shmget ipc/shm.c:745 [inline]
>                     __x64_sys_shmget+0x139/0x1a0 ipc/shm.c:745
>                     do_syscall_64+0xf6/0x7d0 arch/x86/entry/common.c:295
>                     entry_SYSCALL_64_after_hwframe+0x49/0xb3
>    INITIAL USE at:
>                    lock_acquire+0x1f2/0x8f0 kernel/locking/lockdep.c:4923
>                    __raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline]
>                    _raw_spin_lock+0x2a/0x40 kernel/locking/spinlock.c:151
>                    spin_lock include/linux/spinlock.h:353 [inline]
>                    user_shm_lock+0xab/0x230 mm/mlock.c:855
>                    shmem_lock+0x1dd/0x2d0 mm/shmem.c:2184
>                    shmctl_do_lock+0x73f/0x8f0 ipc/shm.c:1111
>                    ksys_shmctl.constprop.0+0x203/0x350 ipc/shm.c:1188
>                    do_syscall_64+0xf6/0x7d0 arch/x86/entry/common.c:295
>                    entry_SYSCALL_64_after_hwframe+0x49/0xb3
>  }
>  ... key      at: [<ffffffff89a5ee98>] shmlock_user_lock+0x18/0x5c0
>  ... acquired at:
>    mark_lock_irq kernel/locking/lockdep.c:3585 [inline]
>    mark_lock+0x624/0xf10 kernel/locking/lockdep.c:3935
>    mark_usage kernel/locking/lockdep.c:3852 [inline]
>    __lock_acquire+0x990/0x4e00 kernel/locking/lockdep.c:4298
>    lock_acquire+0x1f2/0x8f0 kernel/locking/lockdep.c:4923
>    __raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline]
>    _raw_spin_lock+0x2a/0x40 kernel/locking/spinlock.c:151
>    spin_lock include/linux/spinlock.h:353 [inline]
>    user_shm_lock+0xab/0x230 mm/mlock.c:855
>    hugetlb_file_setup+0x4e1/0x677 fs/hugetlbfs/inode.c:1416
>    newseg+0x460/0xe60 ipc/shm.c:652
>    ipcget_new ipc/util.c:344 [inline]
>    ipcget+0xf0/0xcb0 ipc/util.c:643
>    ksys_shmget ipc/shm.c:742 [inline]
>    __do_sys_shmget ipc/shm.c:747 [inline]
>    __se_sys_shmget ipc/shm.c:745 [inline]
>    __x64_sys_shmget+0x139/0x1a0 ipc/shm.c:745
>    do_syscall_64+0xf6/0x7d0 arch/x86/entry/common.c:295
>    entry_SYSCALL_64_after_hwframe+0x49/0xb3
> 
> 
> stack backtrace:
> CPU: 0 PID: 28978 Comm: syz-executor.0 Not tainted 5.6.0-syzkaller #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> Call Trace:
>  __dump_stack lib/dump_stack.c:77 [inline]
>  dump_stack+0x188/0x20d lib/dump_stack.c:118
>  print_irq_inversion_bug kernel/locking/lockdep.c:3448 [inline]
>  check_usage_backwards.cold+0x1d/0x26 kernel/locking/lockdep.c:3499
>  mark_lock_irq kernel/locking/lockdep.c:3585 [inline]
>  mark_lock+0x624/0xf10 kernel/locking/lockdep.c:3935
>  mark_usage kernel/locking/lockdep.c:3852 [inline]
>  __lock_acquire+0x990/0x4e00 kernel/locking/lockdep.c:4298
>  lock_acquire+0x1f2/0x8f0 kernel/locking/lockdep.c:4923
>  __raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline]
>  _raw_spin_lock+0x2a/0x40 kernel/locking/spinlock.c:151
>  spin_lock include/linux/spinlock.h:353 [inline]
>  user_shm_lock+0xab/0x230 mm/mlock.c:855
>  hugetlb_file_setup+0x4e1/0x677 fs/hugetlbfs/inode.c:1416
>  newseg+0x460/0xe60 ipc/shm.c:652
>  ipcget_new ipc/util.c:344 [inline]
>  ipcget+0xf0/0xcb0 ipc/util.c:643
>  ksys_shmget ipc/shm.c:742 [inline]
>  __do_sys_shmget ipc/shm.c:747 [inline]
>  __se_sys_shmget ipc/shm.c:745 [inline]
>  __x64_sys_shmget+0x139/0x1a0 ipc/shm.c:745
>  do_syscall_64+0xf6/0x7d0 arch/x86/entry/common.c:295
>  entry_SYSCALL_64_after_hwframe+0x49/0xb3
> RIP: 0033:0x45c889
> Code: ad b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 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 0f 83 7b b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00
> RSP: 002b:00007f8090c57c78 EFLAGS: 00000246 ORIG_RAX: 000000000000001d
> RAX: ffffffffffffffda RBX: 00007f8090c586d4 RCX: 000000000045c889
> RDX: 0000000078000e02 RSI: 0000000000003000 RDI: 0400000000000000
> RBP: 000000000076bf00 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000020ff2000 R11: 0000000000000246 R12: 00000000ffffffff
> R13: 0000000000000b5d R14: 00000000004cd951 R15: 000000000076bf0c
> 
> 
> ---
> This bug 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 bug report. See:
> https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

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