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  • * Re: possible deadlock in ovl_write_iter
           [not found] <00000000000074e10d0576cc48f1@google.com>
           [not found] ` <CAOQ4uxik7QbQVBQbaPWCxPG90HuJK=T0yckoyfe5NjLHhg898Q@mail.gmail.com>
    @ 2018-11-27  7:06 ` syzbot
      2018-11-27  7:44   ` Amir Goldstein
      2018-11-27 15:07   ` Amir Goldstein
      1 sibling, 2 replies; 7+ messages in thread
    From: syzbot @ 2018-11-27  7:06 UTC (permalink / raw)
      To: amir73il, linux-fsdevel, linux-kernel, linux-unionfs, miklos,
    	syzkaller-bugs
    
    syzbot has found a reproducer for the following crash on:
    
    HEAD commit:    6f8b52ba442c Merge tag 'hwmon-for-v4.20-rc5' of git://git...
    git tree:       upstream
    console output: https://syzkaller.appspot.com/x/log.txt?x=120f3905400000
    kernel config:  https://syzkaller.appspot.com/x/.config?x=c94f9f0c0363db4b
    dashboard link: https://syzkaller.appspot.com/bug?extid=695726bc473f9c36a4b6
    compiler:       gcc (GCC) 8.0.1 20180413 (experimental)
    syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=10cad225400000
    C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=13813093400000
    
    IMPORTANT: if you fix the bug, please add the following tag to the commit:
    Reported-by: syzbot+695726bc473f9c36a4b6@syzkaller.appspotmail.com
    
    overlayfs: filesystem on './file0' not supported as upperdir
    
    ======================================================
    WARNING: possible circular locking dependency detected
    4.20.0-rc4+ #351 Not tainted
    ------------------------------------------------------
    syz-executor338/5996 is trying to acquire lock:
    00000000b59bb66d (&ovl_i_mutex_key[depth]){+.+.}, at: inode_lock  
    include/linux/fs.h:757 [inline]
    00000000b59bb66d (&ovl_i_mutex_key[depth]){+.+.}, at:  
    ovl_write_iter+0x151/0xd10 fs/overlayfs/file.c:231
    
    but task is already holding lock:
    00000000e0274330 (&pipe->mutex/1){+.+.}, at: pipe_lock_nested fs/pipe.c:62  
    [inline]
    00000000e0274330 (&pipe->mutex/1){+.+.}, at: pipe_lock+0x6e/0x80  
    fs/pipe.c:70
    
    which lock already depends on the new lock.
    
    
    the existing dependency chain (in reverse order) is:
    
    -> #2 (&pipe->mutex/1){+.+.}:
            __mutex_lock_common kernel/locking/mutex.c:925 [inline]
            __mutex_lock+0x166/0x16f0 kernel/locking/mutex.c:1072
            mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:1087
            pipe_lock_nested fs/pipe.c:62 [inline]
            pipe_lock+0x6e/0x80 fs/pipe.c:70
            iter_file_splice_write+0x27d/0x1050 fs/splice.c:700
            do_splice_from fs/splice.c:851 [inline]
            do_splice+0x64a/0x1430 fs/splice.c:1147
            __do_sys_splice fs/splice.c:1414 [inline]
            __se_sys_splice fs/splice.c:1394 [inline]
            __x64_sys_splice+0x2c1/0x330 fs/splice.c:1394
            do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
            entry_SYSCALL_64_after_hwframe+0x49/0xbe
    
    -> #1 (sb_writers#3){.+.+}:
            percpu_down_read_preempt_disable include/linux/percpu-rwsem.h:36  
    [inline]
            percpu_down_read include/linux/percpu-rwsem.h:59 [inline]
            __sb_start_write+0x214/0x370 fs/super.c:1387
            sb_start_write include/linux/fs.h:1597 [inline]
            mnt_want_write+0x3f/0xc0 fs/namespace.c:360
            ovl_want_write+0x76/0xa0 fs/overlayfs/util.c:24
            ovl_setattr+0x10b/0xaf0 fs/overlayfs/inode.c:30
            notify_change+0xbde/0x1110 fs/attr.c:334
            do_truncate+0x1bd/0x2d0 fs/open.c:63
            handle_truncate fs/namei.c:3008 [inline]
            do_last fs/namei.c:3424 [inline]
            path_openat+0x375f/0x5150 fs/namei.c:3534
            do_filp_open+0x255/0x380 fs/namei.c:3564
            do_sys_open+0x568/0x700 fs/open.c:1063
            __do_sys_openat fs/open.c:1090 [inline]
            __se_sys_openat fs/open.c:1084 [inline]
            __x64_sys_openat+0x9d/0x100 fs/open.c:1084
            do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
            entry_SYSCALL_64_after_hwframe+0x49/0xbe
    
    -> #0 (&ovl_i_mutex_key[depth]){+.+.}:
            lock_acquire+0x1ed/0x520 kernel/locking/lockdep.c:3844
            down_write+0x8a/0x130 kernel/locking/rwsem.c:70
            inode_lock include/linux/fs.h:757 [inline]
            ovl_write_iter+0x151/0xd10 fs/overlayfs/file.c:231
            call_write_iter include/linux/fs.h:1857 [inline]
            new_sync_write fs/read_write.c:474 [inline]
            __vfs_write+0x6b8/0x9f0 fs/read_write.c:487
            __kernel_write+0x10c/0x370 fs/read_write.c:506
            write_pipe_buf+0x180/0x240 fs/splice.c:797
            splice_from_pipe_feed fs/splice.c:503 [inline]
            __splice_from_pipe+0x38b/0x7c0 fs/splice.c:627
            splice_from_pipe+0x1ec/0x340 fs/splice.c:662
            default_file_splice_write+0x3c/0x90 fs/splice.c:809
            do_splice_from fs/splice.c:851 [inline]
            do_splice+0x64a/0x1430 fs/splice.c:1147
            __do_sys_splice fs/splice.c:1414 [inline]
            __se_sys_splice fs/splice.c:1394 [inline]
            __x64_sys_splice+0x2c1/0x330 fs/splice.c:1394
            do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
            entry_SYSCALL_64_after_hwframe+0x49/0xbe
    
    other info that might help us debug this:
    
    Chain exists of:
       &ovl_i_mutex_key[depth] --> sb_writers#3 --> &pipe->mutex/1
    
      Possible unsafe locking scenario:
    
            CPU0                    CPU1
            ----                    ----
       lock(&pipe->mutex/1);
                                    lock(sb_writers#3);
                                    lock(&pipe->mutex/1);
       lock(&ovl_i_mutex_key[depth]);
    
      *** DEADLOCK ***
    
    2 locks held by syz-executor338/5996:
      #0: 00000000024e7b73 (sb_writers#8){.+.+}, at: file_start_write  
    include/linux/fs.h:2810 [inline]
      #0: 00000000024e7b73 (sb_writers#8){.+.+}, at: do_splice+0xd2e/0x1430  
    fs/splice.c:1146
      #1: 00000000e0274330 (&pipe->mutex/1){+.+.}, at: pipe_lock_nested  
    fs/pipe.c:62 [inline]
      #1: 00000000e0274330 (&pipe->mutex/1){+.+.}, at: pipe_lock+0x6e/0x80  
    fs/pipe.c:70
    
    stack backtrace:
    CPU: 0 PID: 5996 Comm: syz-executor338 Not tainted 4.20.0-rc4+ #351
    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+0x244/0x39d lib/dump_stack.c:113
      print_circular_bug.isra.35.cold.54+0x1bd/0x27d  
    kernel/locking/lockdep.c:1221
      check_prev_add kernel/locking/lockdep.c:1863 [inline]
      check_prevs_add kernel/locking/lockdep.c:1976 [inline]
      validate_chain kernel/locking/lockdep.c:2347 [inline]
      __lock_acquire+0x3399/0x4c20 kernel/locking/lockdep.c:3341
      lock_acquire+0x1ed/0x520 kernel/locking/lockdep.c:3844
      down_write+0x8a/0x130 kernel/locking/rwsem.c:70
      inode_lock include/linux/fs.h:757 [inline]
      ovl_write_iter+0x151/0xd10 fs/overlayfs/file.c:231
      call_write_iter include/linux/fs.h:1857 [inline]
      new_sync_write fs/read_write.c:474 [inline]
      __vfs_write+0x6b8/0x9f0 fs/read_write.c:487
      __kernel_write+0x10c/0x370 fs/read_write.c:506
      write_pipe_buf+0x180/0x240 fs/splice.c:797
      splice_from_pipe_feed fs/splice.c:503 [inline]
      __splice_from_pipe+0x38b/0x7c0 fs/splice.c:627
      splice_from_pipe+0x1ec/0x340 fs/splice.c:662
      default_file_splice_write+0x3c/0x90 fs/splice.c:809
      do_splice_from fs/splice.c:851 [inline]
      do_splice+0x64a/0x1430 fs/splice.c:1147
      __do_sys_splice fs/splice.c:1414 [inline]
      __se_sys_splice fs/splice.c:1394 [inline]
      __x64_sys_splice+0x2c1/0x330 fs/splice.c:1394
      do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
      entry_SYSCALL_64_after_hwframe+0x49/0xbe
    RIP: 0033:0x445ad9
    Code: e8 5c b7 02 00 48 83 c4 18 c3 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 0f 83 2b 12 fc ff c3 66 2e 0f 1f 84 00 00 00 00
    RSP: 002b:00007f18e3f71cd8 EFLAGS: 00000216 ORIG_RAX: 0000000000000113
    RAX: ffffffffffffffda RBX: 00000000006dac78 RCX: 0000000000445ad9
    RDX: 000000000000000a RSI: 0000000000000000 RDI: 0000000000000007
    RBP: 00000000006dac70 R08: 000100000000000a R09: 0000000000000007
    R10: 0000000000000000 R11: 0000000000000216 R12: 00000000006dac7c
    R13: 00007ffde0706e9f R14: 00007f18e3f729c0 R15: 00000000006dad4c
    
    ^ permalink raw reply	[flat|nested] 7+ messages in thread

  • end of thread, other threads:[~2018-11-28  3:11 UTC | newest]
    
    Thread overview: 7+ messages (download: mbox.gz / follow: Atom feed)
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         [not found] <00000000000074e10d0576cc48f1@google.com>
         [not found] ` <CAOQ4uxik7QbQVBQbaPWCxPG90HuJK=T0yckoyfe5NjLHhg898Q@mail.gmail.com>
    2018-09-27  3:51   ` possible deadlock in ovl_write_iter Amir Goldstein
    2018-11-27  7:06 ` syzbot
    2018-11-27  7:44   ` Amir Goldstein
    2018-11-27 14:12     ` Dmitry Vyukov
    2018-11-27 15:07   ` Amir Goldstein
    2018-11-27 15:48     ` Dmitry Vyukov
    2018-11-27 16:13       ` Amir Goldstein
    

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