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From: Ryusuke Konishi <konishi.ryusuke@gmail.com>
Date: Sun, 19 May 2024 04:16:31 +0900
Message-ID: <CAKFNMo=rpJ7WsqPL5G+Us_P8aaGSMn-LnS4HNdkoJk_hSWf20Q@mail.gmail.com>
Subject: Re: [syzbot] [nilfs?] possible deadlock in nilfs_transaction_begin
To: syzbot <syzbot+77c39f023a0cb2e4c149@syzkaller.appspotmail.com>
Cc: linux-kernel@vger.kernel.org, linux-nilfs@vger.kernel.org, 
	syzkaller-bugs@googlegroups.com
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On Sat, May 18, 2024 at 9:29=E2=80=AFPM syzbot
<syzbot+77c39f023a0cb2e4c149@syzkaller.appspotmail.com> wrote:
>
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit:    a5131c3fdf26 Merge tag 'x86-shstk-2024-05-13' of git://gi=
t..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=3D144c6e0498000=
0
> kernel config:  https://syzkaller.appspot.com/x/.config?x=3Dfdb182f40cdd6=
6f7
> dashboard link: https://syzkaller.appspot.com/bug?extid=3D77c39f023a0cb2e=
4c149
> compiler:       gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for D=
ebian) 2.40
> userspace arch: i386
>
> Unfortunately, I don't have any reproducer for this issue yet.
>
> Downloadable assets:
> disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/7=
bc7510fe41f/non_bootable_disk-a5131c3f.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/6d23116dab9c/vmlinu=
x-a5131c3f.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/dd8b9de9af4f/b=
zImage-a5131c3f.xz
>
> IMPORTANT: if you fix the issue, please add the following tag to the comm=
it:
> Reported-by: syzbot+77c39f023a0cb2e4c149@syzkaller.appspotmail.com
>
> NILFS (loop2): inode bitmap is inconsistent for reserved inodes
> NILFS (loop2): repaired inode bitmap for reserved inodes
> =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=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D
> WARNING: possible circular locking dependency detected
> 6.9.0-syzkaller-01768-ga5131c3fdf26 #0 Not tainted
> ------------------------------------------------------
> syz-executor.2/23478 is trying to acquire lock:
> ffffffff8d938460 (fs_reclaim){+.+.}-{0:0}, at: might_alloc include/linux/=
sched/mm.h:312 [inline]
> ffffffff8d938460 (fs_reclaim){+.+.}-{0:0}, at: prepare_alloc_pages.constp=
rop.0+0x155/0x560 mm/page_alloc.c:4346
>
> but task is already holding lock:
> ffff888026c5c2a0 (&nilfs->ns_segctor_sem){++++}-{3:3}, at: nilfs_transact=
ion_begin+0x326/0xa40 fs/nilfs2/segment.c:223
>
> which lock already depends on the new lock.
>
>
> the existing dependency chain (in reverse order) is:
>
> -> #2 (&nilfs->ns_segctor_sem){++++}-{3:3}:
>        down_read+0x9a/0x330 kernel/locking/rwsem.c:1526
>        nilfs_transaction_begin+0x326/0xa40 fs/nilfs2/segment.c:223
>        nilfs_create+0xb7/0x320 fs/nilfs2/namei.c:82
>        lookup_open.isra.0+0x10a1/0x13c0 fs/namei.c:3505
>        open_last_lookups fs/namei.c:3574 [inline]
>        path_openat+0x92f/0x2990 fs/namei.c:3804
>        do_filp_open+0x1dc/0x430 fs/namei.c:3834
>        do_sys_openat2+0x17a/0x1e0 fs/open.c:1406
>        do_sys_open fs/open.c:1421 [inline]
>        __do_compat_sys_openat fs/open.c:1481 [inline]
>        __se_compat_sys_openat fs/open.c:1479 [inline]
>        __ia32_compat_sys_openat+0x16e/0x210 fs/open.c:1479
>        do_syscall_32_irqs_on arch/x86/entry/common.c:165 [inline]
>        __do_fast_syscall_32+0x75/0x120 arch/x86/entry/common.c:386
>        do_fast_syscall_32+0x32/0x80 arch/x86/entry/common.c:411
>        entry_SYSENTER_compat_after_hwframe+0x84/0x8e
>
> -> #1 (sb_internal#5){.+.+}-{0:0}:
>        percpu_down_read include/linux/percpu-rwsem.h:51 [inline]
>        __sb_start_write include/linux/fs.h:1661 [inline]
>        sb_start_intwrite include/linux/fs.h:1844 [inline]
>        nilfs_transaction_begin+0x21b/0xa40 fs/nilfs2/segment.c:220
>        nilfs_dirty_inode+0x1a4/0x270 fs/nilfs2/inode.c:1153
>        __mark_inode_dirty+0x1f0/0xe70 fs/fs-writeback.c:2486
>        mark_inode_dirty_sync include/linux/fs.h:2426 [inline]
>        iput.part.0+0x5b/0x7f0 fs/inode.c:1764
>        iput+0x5c/0x80 fs/inode.c:1757
>        dentry_unlink_inode+0x295/0x440 fs/dcache.c:400
>        __dentry_kill+0x1d0/0x600 fs/dcache.c:603
>        shrink_kill fs/dcache.c:1048 [inline]
>        shrink_dentry_list+0x140/0x5d0 fs/dcache.c:1075
>        prune_dcache_sb+0xeb/0x150 fs/dcache.c:1156
>        super_cache_scan+0x32a/0x550 fs/super.c:221
>        do_shrink_slab+0x44f/0x11c0 mm/shrinker.c:435
>        shrink_slab_memcg mm/shrinker.c:548 [inline]
>        shrink_slab+0xa87/0x1310 mm/shrinker.c:626
>        shrink_one+0x493/0x7c0 mm/vmscan.c:4774
>        shrink_many mm/vmscan.c:4835 [inline]
>        lru_gen_shrink_node+0x89f/0x1750 mm/vmscan.c:4935
>        shrink_node mm/vmscan.c:5894 [inline]
>        kswapd_shrink_node mm/vmscan.c:6704 [inline]
>        balance_pgdat+0x10d1/0x1a10 mm/vmscan.c:6895
>        kswapd+0x5ea/0xbf0 mm/vmscan.c:7164
>        kthread+0x2c1/0x3a0 kernel/kthread.c:388
>        ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:147
>        ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
>
> -> #0 (fs_reclaim){+.+.}-{0:0}:
>        check_prev_add kernel/locking/lockdep.c:3134 [inline]
>        check_prevs_add kernel/locking/lockdep.c:3253 [inline]
>        validate_chain kernel/locking/lockdep.c:3869 [inline]
>        __lock_acquire+0x2478/0x3b30 kernel/locking/lockdep.c:5137
>        lock_acquire kernel/locking/lockdep.c:5754 [inline]
>        lock_acquire+0x1b1/0x560 kernel/locking/lockdep.c:5719
>        __fs_reclaim_acquire mm/page_alloc.c:3698 [inline]
>        fs_reclaim_acquire+0x102/0x160 mm/page_alloc.c:3712
>        might_alloc include/linux/sched/mm.h:312 [inline]
>        prepare_alloc_pages.constprop.0+0x155/0x560 mm/page_alloc.c:4346
>        __alloc_pages+0x194/0x2460 mm/page_alloc.c:4564
>        alloc_pages_mpol+0x275/0x610 mm/mempolicy.c:2264
>        folio_alloc+0x1e/0x40 mm/mempolicy.c:2342
>        filemap_alloc_folio+0x3ba/0x490 mm/filemap.c:984
>        __filemap_get_folio+0x527/0xa90 mm/filemap.c:1926
>        pagecache_get_page+0x2c/0x260 mm/folio-compat.c:93
>        block_write_begin+0x38/0x4a0 fs/buffer.c:2209
>        nilfs_write_begin+0x9f/0x1a0 fs/nilfs2/inode.c:262
>        page_symlink+0x356/0x450 fs/namei.c:5236
>        nilfs_symlink+0x23c/0x3c0 fs/nilfs2/namei.c:153
>        vfs_symlink fs/namei.c:4489 [inline]
>        vfs_symlink+0x3e8/0x630 fs/namei.c:4473
>        do_symlinkat+0x263/0x310 fs/namei.c:4515
>        __do_sys_symlink fs/namei.c:4536 [inline]
>        __se_sys_symlink fs/namei.c:4534 [inline]
>        __ia32_sys_symlink+0x78/0xa0 fs/namei.c:4534
>        do_syscall_32_irqs_on arch/x86/entry/common.c:165 [inline]
>        __do_fast_syscall_32+0x75/0x120 arch/x86/entry/common.c:386
>        do_fast_syscall_32+0x32/0x80 arch/x86/entry/common.c:411
>        entry_SYSENTER_compat_after_hwframe+0x84/0x8e
>
> other info that might help us debug this:
>
> Chain exists of:
>   fs_reclaim --> sb_internal#5 --> &nilfs->ns_segctor_sem
>
>  Possible unsafe locking scenario:
>
>        CPU0                    CPU1
>        ----                    ----
>   rlock(&nilfs->ns_segctor_sem);
>                                lock(sb_internal#5);
>                                lock(&nilfs->ns_segctor_sem);
>   lock(fs_reclaim);
>
>  *** DEADLOCK ***
>
> 4 locks held by syz-executor.2/23478:
>  #0: ffff888000c0c420 (sb_writers#32){.+.+}-{0:0}, at: filename_create+0x=
10d/0x530 fs/namei.c:3893
>  #1: ffff88804b284f88 (&type->i_mutex_dir_key#23/1){+.+.}-{3:3}, at: inod=
e_lock_nested include/linux/fs.h:826 [inline]
>  #1: ffff88804b284f88 (&type->i_mutex_dir_key#23/1){+.+.}-{3:3}, at: file=
name_create+0x1c2/0x530 fs/namei.c:3900
>  #2: ffff888000c0c610 (sb_internal#5){.+.+}-{0:0}, at: nilfs_symlink+0x11=
4/0x3c0 fs/nilfs2/namei.c:140
>  #3: ffff888026c5c2a0 (&nilfs->ns_segctor_sem){++++}-{3:3}, at: nilfs_tra=
nsaction_begin+0x326/0xa40 fs/nilfs2/segment.c:223
>
> stack backtrace:
> CPU: 2 PID: 23478 Comm: syz-executor.2 Not tainted 6.9.0-syzkaller-01768-=
ga5131c3fdf26 #0
> Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.=
16.2-1 04/01/2014
> Call Trace:
>  <TASK>
>  __dump_stack lib/dump_stack.c:88 [inline]
>  dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:114
>  check_noncircular+0x31a/0x400 kernel/locking/lockdep.c:2187
>  check_prev_add kernel/locking/lockdep.c:3134 [inline]
>  check_prevs_add kernel/locking/lockdep.c:3253 [inline]
>  validate_chain kernel/locking/lockdep.c:3869 [inline]
>  __lock_acquire+0x2478/0x3b30 kernel/locking/lockdep.c:5137
>  lock_acquire kernel/locking/lockdep.c:5754 [inline]
>  lock_acquire+0x1b1/0x560 kernel/locking/lockdep.c:5719
>  __fs_reclaim_acquire mm/page_alloc.c:3698 [inline]
>  fs_reclaim_acquire+0x102/0x160 mm/page_alloc.c:3712
>  might_alloc include/linux/sched/mm.h:312 [inline]
>  prepare_alloc_pages.constprop.0+0x155/0x560 mm/page_alloc.c:4346
>  __alloc_pages+0x194/0x2460 mm/page_alloc.c:4564
>  alloc_pages_mpol+0x275/0x610 mm/mempolicy.c:2264
>  folio_alloc+0x1e/0x40 mm/mempolicy.c:2342
>  filemap_alloc_folio+0x3ba/0x490 mm/filemap.c:984
>  __filemap_get_folio+0x527/0xa90 mm/filemap.c:1926
>  pagecache_get_page+0x2c/0x260 mm/folio-compat.c:93
>  block_write_begin+0x38/0x4a0 fs/buffer.c:2209
>  nilfs_write_begin+0x9f/0x1a0 fs/nilfs2/inode.c:262
>  page_symlink+0x356/0x450 fs/namei.c:5236
>  nilfs_symlink+0x23c/0x3c0 fs/nilfs2/namei.c:153
>  vfs_symlink fs/namei.c:4489 [inline]
>  vfs_symlink+0x3e8/0x630 fs/namei.c:4473
>  do_symlinkat+0x263/0x310 fs/namei.c:4515
>  __do_sys_symlink fs/namei.c:4536 [inline]
>  __se_sys_symlink fs/namei.c:4534 [inline]
>  __ia32_sys_symlink+0x78/0xa0 fs/namei.c:4534
>  do_syscall_32_irqs_on arch/x86/entry/common.c:165 [inline]
>  __do_fast_syscall_32+0x75/0x120 arch/x86/entry/common.c:386
>  do_fast_syscall_32+0x32/0x80 arch/x86/entry/common.c:411
>  entry_SYSENTER_compat_after_hwframe+0x84/0x8e
> RIP: 0023:0xf734f579
> Code: b8 01 10 06 03 74 b4 01 10 07 03 74 b0 01 10 08 03 74 d8 01 00 00 0=
0 00 00 00 00 00 00 00 00 00 00 51 52 55 89 e5 0f 34 cd 80 <5d> 5a 59 c3 90=
 90 90 90 8d b4 26 00 00 00 00 8d b4 26 00 00 00 00
> RSP: 002b:00000000f5f415ac EFLAGS: 00000292 ORIG_RAX: 0000000000000053
> RAX: ffffffffffffffda RBX: 0000000020000340 RCX: 0000000020000100
> RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
> RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000292 R12: 0000000000000000
> R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
>  </TASK>
> ----------------
> Code disassembly (best guess), 2 bytes skipped:
>    0:   10 06                   adc    %al,(%rsi)
>    2:   03 74 b4 01             add    0x1(%rsp,%rsi,4),%esi
>    6:   10 07                   adc    %al,(%rdi)
>    8:   03 74 b0 01             add    0x1(%rax,%rsi,4),%esi
>    c:   10 08                   adc    %cl,(%rax)
>    e:   03 74 d8 01             add    0x1(%rax,%rbx,8),%esi
>   1e:   00 51 52                add    %dl,0x52(%rcx)
>   21:   55                      push   %rbp
>   22:   89 e5                   mov    %esp,%ebp
>   24:   0f 34                   sysenter
>   26:   cd 80                   int    $0x80
> * 28:   5d                      pop    %rbp <-- trapping instruction
>   29:   5a                      pop    %rdx
>   2a:   59                      pop    %rcx
>   2b:   c3                      ret
>   2c:   90                      nop
>   2d:   90                      nop
>   2e:   90                      nop
>   2f:   90                      nop
>   30:   8d b4 26 00 00 00 00    lea    0x0(%rsi,%riz,1),%esi
>   37:   8d b4 26 00 00 00 00    lea    0x0(%rsi,%riz,1),%esi
>
>
> ---
> 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 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

This issue seems to be the same as the report below, but I don't have
time to look into it in detail right now, so I'll put it on hold.

https://syzkaller.appspot.com/bug?extid=3Dca73f5a22aec76875d85

It looks like the GFP flags in the symlink's page cache allocation are
causing the circular lock dependency.

Ryusuke Konishi