Re: [syzbot] BUG: spinlock bad magic in erofs_pcpubuf_growsize

[Gao Xiang]

(avoid Cc such many people...)

On 2021/4/10 01:59, syzbot wrote:
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit:    9c54130c Add linux-next specific files for 20210406
> git tree:       linux-next
> console output: https://syzkaller.appspot.com/x/log.txt?x=1654617ed00000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=d125958c3995ddcd
> dashboard link: https://syzkaller.appspot.com/bug?extid=d6a0e4b80bd39f54c2f6
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=101a5786d00000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1147dd0ed00000
>
> The issue was bisected to:
>
> commit 997acaf6b4b59c6a9c259740312a69ea549cc684
> Author: Mark Rutland <mark.rutland@xxxxxxx>
> Date:   Mon Jan 11 15:37:07 2021 +0000
>
>      lockdep: report broken irq restoration
>
> bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=11d8d7aad00000
> final oops:     https://syzkaller.appspot.com/x/report.txt?x=13d8d7aad00000
> console output: https://syzkaller.appspot.com/x/log.txt?x=15d8d7aad00000
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+d6a0e4b80bd39f54c2f6@xxxxxxxxxxxxxxxxxxxxxxxxx
> Fixes: 997acaf6b4b5 ("lockdep: report broken irq restoration")
>
> loop0: detected capacity change from 0 to 31
> BUG: spinlock bad magic on CPU#1, syz-executor062/8434
>   lock: 0xffff8880b9c31d60, .magic: 00000000, .owner: <none>/-1, .owner_cpu: 0
> CPU: 1 PID: 8434 Comm: syz-executor062 Not tainted 5.12.0-rc6-next-20210406-syzkaller #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> Call Trace:
>   __dump_stack lib/dump_stack.c:79 [inline]
>   dump_stack+0x141/0x1d7 lib/dump_stack.c:120
>   debug_spin_lock_before kernel/locking/spinlock_debug.c:83 [inline]
>   do_raw_spin_lock+0x216/0x2b0 kernel/locking/spinlock_debug.c:112
>   erofs_pcpubuf_growsize+0x36f/0x620 fs/erofs/pcpubuf.c:83

This issue only existed in some linux-next (2021/04/06 ~ 2021/04/06) and
Linux upstream never hitted such issue, so:

#syz test: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/ v6.3-rc6

#syz invalid

Thanks,
Gao Xiang

>   z_erofs_load_lz4_config+0x1ef/0x3e0 fs/erofs/decompressor.c:64
>   erofs_read_superblock fs/erofs/super.c:331 [inline]
>   erofs_fc_fill_super+0xe84/0x1d10 fs/erofs/super.c:499
>   get_tree_bdev+0x440/0x760 fs/super.c:1293
>   vfs_get_tree+0x89/0x2f0 fs/super.c:1498
>   do_new_mount fs/namespace.c:2905 [inline]
>   path_mount+0x132a/0x1fa0 fs/namespace.c:3235
>   do_mount fs/namespace.c:3248 [inline]
>   __do_sys_mount fs/namespace.c:3456 [inline]
>   __se_sys_mount fs/namespace.c:3433 [inline]
>   __x64_sys_mount+0x27f/0x300 fs/namespace.c:3433
>   do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
>   entry_SYSCALL_64_after_hwframe+0x44/0xae
> RIP: 0033:0x444f7a
> Code: 83 c4 08 5b 5d c3 66 2e 0f 1f 84 00 00 00 00 00 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 49 89 ca b8 a5 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 c0 ff ff ff f7 d8 64 89 01 48
> RSP: 002b:00007ffe1fa3c2a8 EFLAGS: 00000286 ORIG_RAX: 00000000000000a5
> RAX: ffffffffffffffda RBX: 00007ffe1fa3c300 RCX: 0000000000444f7a
> RDX: 0000000020000000 RSI: 0000000020000100 RDI: 00007ffe1fa3c2c0
> RBP: 00007ffe1fa3c2c0 R08: 00007ffe1fa3c300 R09:
>
>
> ---
> 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@xxxxxxxxxxxxxxxx.
>
> syzbot will keep track of this issue. See:
> https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
> For information about bisection process see: https://goo.gl/tpsmEJ#bisection
> syzbot can test patches for this issue, for details see:
> https://goo.gl/tpsmEJ#testing-patches