Message-ID: <94eb2c05f6a018dc21055d39c05b@google.com>
Date:   Sun, 05 Nov 2017 02:25:00 -0800
From:   syzbot 
        <bot+f99f3a0db9007f4f4e32db54229a240c4fe57c15@...kaller.appspotmail.com>
To:     akpm@...ux-foundation.org, hannes@...xchg.org, jack@...e.cz,
        jlayton@...hat.com, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, npiggin@...il.com, rgoldwyn@...e.com,
        ross.zwisler@...ux.intel.com, syzkaller-bugs@...glegroups.com,
        viro@...iv.linux.org.uk
Subject: possible deadlock in generic_file_write_iter

Hello,

syzkaller hit the following crash on  
7a95bdb092c66b6473aa2fc848862ae557ab08f7
git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/master
compiler: gcc (GCC) 7.1.1 20170620
.config is attached
Raw console output is attached.
C reproducer is attached
syzkaller reproducer is attached. See https://goo.gl/kgGztJ
for information about syzkaller reproducers


======================================================
WARNING: possible circular locking dependency detected
4.13.0+ #84 Not tainted
------------------------------------------------------
loop0/2986 is trying to acquire lock:
  (&sb->s_type->i_mutex_key#9){++++}, at: [<ffffffff8186f9ec>] inode_lock  
include/linux/fs.h:712 [inline]
  (&sb->s_type->i_mutex_key#9){++++}, at: [<ffffffff8186f9ec>]  
generic_file_write_iter+0xdc/0x7a0 mm/filemap.c:3151

but now in release context of a crosslock acquired at the following:
  ((complete)&ret.event){+.+.}, at: [<ffffffff822a055e>]  
submit_bio_wait+0x15e/0x200 block/bio.c:953

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #4 ((complete)&ret.event){+.+.}:
        check_prevs_add kernel/locking/lockdep.c:2020 [inline]
        validate_chain kernel/locking/lockdep.c:2469 [inline]
        __lock_acquire+0x328f/0x4620 kernel/locking/lockdep.c:3498
        lock_acquire+0x1d5/0x580 kernel/locking/lockdep.c:4002
        complete_acquire include/linux/completion.h:39 [inline]
        __wait_for_common kernel/sched/completion.c:108 [inline]
        wait_for_common_io kernel/sched/completion.c:128 [inline]
        wait_for_completion_io+0xc8/0x770 kernel/sched/completion.c:176
        submit_bio_wait+0x15e/0x200 block/bio.c:953
        blkdev_issue_zeroout+0x13c/0x1d0 block/blk-lib.c:370
        sb_issue_zeroout include/linux/blkdev.h:1367 [inline]
        ext4_init_inode_table+0x4fd/0xdb1 fs/ext4/ialloc.c:1447
        ext4_run_li_request fs/ext4/super.c:2867 [inline]
        ext4_lazyinit_thread+0x81a/0xd40 fs/ext4/super.c:2961
        kthread+0x39c/0x470 kernel/kthread.c:231
        ret_from_fork+0x2a/0x40 arch/x86/entry/entry_64.S:431

-> #3 (&meta_group_info[i]->alloc_sem){++++}:
        check_prevs_add kernel/locking/lockdep.c:2020 [inline]
        validate_chain kernel/locking/lockdep.c:2469 [inline]
        __lock_acquire+0x328f/0x4620 kernel/locking/lockdep.c:3498
        lock_acquire+0x1d5/0x580 kernel/locking/lockdep.c:4002
        down_read+0x96/0x150 kernel/locking/rwsem.c:23
        __ext4_new_inode+0x26dc/0x4f00 fs/ext4/ialloc.c:1056
        ext4_symlink+0x2d9/0xae0 fs/ext4/namei.c:3118
        vfs_symlink+0x323/0x560 fs/namei.c:4116
        SYSC_symlinkat fs/namei.c:4143 [inline]
        SyS_symlinkat fs/namei.c:4123 [inline]
        SYSC_symlink fs/namei.c:4156 [inline]
        SyS_symlink+0x134/0x200 fs/namei.c:4154
        entry_SYSCALL_64_fastpath+0x1f/0xbe

-> #2 (jbd2_handle){.+.+}:
        check_prevs_add kernel/locking/lockdep.c:2020 [inline]
        validate_chain kernel/locking/lockdep.c:2469 [inline]
        __lock_acquire+0x328f/0x4620 kernel/locking/lockdep.c:3498
        lock_acquire+0x1d5/0x580 kernel/locking/lockdep.c:4002
        start_this_handle+0x4b8/0x1080 fs/jbd2/transaction.c:390
        jbd2__journal_start+0x389/0x9f0 fs/jbd2/transaction.c:444
        __ext4_journal_start_sb+0x15f/0x550 fs/ext4/ext4_jbd2.c:80
        __ext4_journal_start fs/ext4/ext4_jbd2.h:314 [inline]
        ext4_dirty_inode+0x56/0xa0 fs/ext4/inode.c:5859
        __mark_inode_dirty+0x912/0x1170 fs/fs-writeback.c:2096
        generic_update_time+0x1b2/0x270 fs/inode.c:1649
        update_time fs/inode.c:1665 [inline]
        touch_atime+0x26d/0x2f0 fs/inode.c:1737
        file_accessed include/linux/fs.h:2036 [inline]
        ext4_file_mmap+0x161/0x1b0 fs/ext4/file.c:350
        call_mmap include/linux/fs.h:1748 [inline]
        mmap_region+0xa99/0x15a0 mm/mmap.c:1690
        do_mmap+0x6a1/0xd50 mm/mmap.c:1468
        do_mmap_pgoff include/linux/mm.h:2150 [inline]
        vm_mmap_pgoff+0x1de/0x280 mm/util.c:333
        SYSC_mmap_pgoff mm/mmap.c:1518 [inline]
        SyS_mmap_pgoff+0x462/0x5f0 mm/mmap.c:1476
        SYSC_mmap arch/x86/kernel/sys_x86_64.c:99 [inline]
        SyS_mmap+0x16/0x20 arch/x86/kernel/sys_x86_64.c:90
        entry_SYSCALL_64_fastpath+0x1f/0xbe

-> #1 (&mm->mmap_sem){++++}:
        check_prevs_add kernel/locking/lockdep.c:2020 [inline]
        validate_chain kernel/locking/lockdep.c:2469 [inline]
        __lock_acquire+0x328f/0x4620 kernel/locking/lockdep.c:3498
        lock_acquire+0x1d5/0x580 kernel/locking/lockdep.c:4002
        __might_fault+0x13a/0x1d0 mm/memory.c:4502
        _copy_to_user+0x2c/0xc0 lib/usercopy.c:24
        copy_to_user include/linux/uaccess.h:154 [inline]
        filldir+0x1a7/0x320 fs/readdir.c:196
        dir_emit_dot include/linux/fs.h:3314 [inline]
        dir_emit_dots include/linux/fs.h:3325 [inline]
        dcache_readdir+0x12d/0x5e0 fs/libfs.c:192
        iterate_dir+0x4b2/0x5d0 fs/readdir.c:51
        SYSC_getdents fs/readdir.c:231 [inline]
        SyS_getdents+0x225/0x450 fs/readdir.c:212
        entry_SYSCALL_64_fastpath+0x1f/0xbe

-> #0 (&sb->s_type->i_mutex_key#9){++++}:
        down_write+0x87/0x120 kernel/locking/rwsem.c:53
        inode_lock include/linux/fs.h:712 [inline]
        generic_file_write_iter+0xdc/0x7a0 mm/filemap.c:3151
        call_write_iter include/linux/fs.h:1743 [inline]
        do_iter_readv_writev+0x531/0x7f0 fs/read_write.c:650
        do_iter_write+0x15a/0x540 fs/read_write.c:929
        vfs_iter_write+0x77/0xb0 fs/read_write.c:942

other info that might help us debug this:

Chain exists of:
   &sb->s_type->i_mutex_key#9 --> &meta_group_info[i]->alloc_sem -->  
(complete)&ret.event

  Possible unsafe locking scenario by crosslock:

        CPU0                    CPU1
        ----                    ----
   lock(&meta_group_info[i]->alloc_sem);
   lock((complete)&ret.event);
                                lock(&sb->s_type->i_mutex_key#9);
                                unlock((complete)&ret.event);

  *** DEADLOCK ***

1 lock held by loop0/2986:
  #0:  (&x->wait#14){..-.}, at: [<ffffffff815263f8>] complete+0x18/0x80  
kernel/sched/completion.c:34

stack backtrace:
CPU: 1 PID: 2986 Comm: loop0 Not tainted 4.13.0+ #84
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
Call Trace:
  __dump_stack lib/dump_stack.c:16 [inline]
  dump_stack+0x194/0x257 lib/dump_stack.c:52
  print_circular_bug+0x503/0x710 kernel/locking/lockdep.c:1259
  check_prev_add+0x865/0x1520 kernel/locking/lockdep.c:1894
  commit_xhlock kernel/locking/lockdep.c:5015 [inline]
  commit_xhlocks kernel/locking/lockdep.c:5059 [inline]
  lock_commit_crosslock+0xe73/0x1d10 kernel/locking/lockdep.c:5098
  complete_release_commit include/linux/completion.h:49 [inline]
  complete+0x24/0x80 kernel/sched/completion.c:39
  submit_bio_wait_endio+0x9c/0xd0 block/bio.c:930
  bio_endio+0x2f8/0x8d0 block/bio.c:1843
  req_bio_endio block/blk-core.c:204 [inline]
  blk_update_request+0x2a6/0xe20 block/blk-core.c:2743
  blk_mq_end_request+0x54/0x120 block/blk-mq.c:509
  lo_complete_rq+0xbe/0x1f0 drivers/block/loop.c:463
  __blk_mq_complete_request+0x38f/0x6c0 block/blk-mq.c:550
  blk_mq_complete_request+0x4f/0x60 block/blk-mq.c:570
  loop_handle_cmd drivers/block/loop.c:1710 [inline]
  loop_queue_work+0x26b/0x3900 drivers/block/loop.c:1719
  kthread_worker_fn+0x340/0x9b0 kernel/kthread.c:635


---
This bug is generated by a dumb bot. It may contain errors.
See https://goo.gl/tpsmEJ for details.
Direct all questions to syzkaller@...glegroups.com.
Please credit me with: Reported-by: syzbot <syzkaller@...glegroups.com>

syzbot will keep track of this bug report.
Once a fix for this bug is committed, please reply to this email with:
#syz fix: exact-commit-title
To mark this as a duplicate of another syzbot report, please reply with:
#syz dup: exact-subject-of-another-report
If it's a one-off invalid bug report, please reply with:
#syz invalid
Note: if the crash happens again, it will cause creation of a new bug  
report.
Note: all commands must start from beginning of the line.

View attachment "config.txt" of type "text/plain" (123749 bytes)

Download attachment "raw.log" of type "application/octet-stream" (7887 bytes)

View attachment "repro.txt" of type "text/plain" (1018 bytes)

Download attachment "repro.c" of type "application/octet-stream" (2684 bytes)

Powered by blists - more mailing lists