Re: [syzbot] WARNING in c_start

[Borislav Petkov]

On Fri, Oct 14, 2022 at 02:16:42PM -0700, syzbot wrote:
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    9c9155a3509a Merge tag 'drm-next-2022-10-14' of git://anon..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=1030f562880000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=557e715ffce7a200
> dashboard link: https://syzkaller.appspot.com/bug?extid=d0fd2bf0dd6da72496dd
> compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
> 
> Unfortunately, I don't have any reproducer for this issue yet.
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+d0fd2bf0dd6da72496dd@xxxxxxxxxxxxxxxxxxxxxxxxx
> 
> ------------[ cut here ]------------
> WARNING: CPU: 1 PID: 3671 at include/linux/cpumask.h:110 cpu_max_bits_warn include/linux/cpumask.h:110 [inline]
> WARNING: CPU: 1 PID: 3671 at include/linux/cpumask.h:110 cpumask_check include/linux/cpumask.h:117 [inline]
> WARNING: CPU: 1 PID: 3671 at include/linux/cpumask.h:110 cpumask_next include/linux/cpumask.h:178 [inline]
> WARNING: CPU: 1 PID: 3671 at include/linux/cpumask.h:110 c_start+0x152/0x1b0 arch/x86/kernel/cpu/proc.c:156
> Modules linked in:
> CPU: 1 PID: 3671 Comm: syz-fuzzer Not tainted 6.0.0-syzkaller-11990-g9c9155a3509a #0
> Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.14.0-2 04/01/2014
> RIP: 0010:cpu_max_bits_warn include/linux/cpumask.h:110 [inline]
> RIP: 0010:cpumask_check include/linux/cpumask.h:117 [inline]
> RIP: 0010:cpumask_next include/linux/cpumask.h:178 [inline]
> RIP: 0010:c_start+0x152/0x1b0 arch/x86/kernel/cpu/proc.c:156
> Code: a0 68 99 8b e8 3f 97 4b 00 5b 5d 4c 89 e0 41 5c 41 5d c3 e8 30 97 4b 00 45 31 e4 5b 4c 89 e0 5d 41 5c 41 5d c3 e8 1e 97 4b 00 <0f> 0b e9 1e ff ff ff 48 c7 c7 40 54 e1 8d e8 fb 19 97 00 e9 6b ff
> RSP: 0018:ffffc90002f27c70 EFLAGS: 00010293
> RAX: 0000000000000000 RBX: ffffffff8de15440 RCX: 0000000000000000
> RDX: ffff88801b3b6100 RSI: ffffffff812ffc02 RDI: 0000000000000004
> RBP: 0000000000000008 R08: 0000000000000004 R09: 0000000000000008
> R10: 0000000000000008 R11: 0000000000000001 R12: ffff88801c29c278
> R13: 0000000000000008 R14: ffff888023b17b3c R15: 0000000000000000
> FS:  000000c00004e890(0000) GS:ffff88802c800000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00007fe53b98da00 CR3: 000000001b4cb000 CR4: 0000000000150ef0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
>  <TASK>
>  seq_read_iter+0x2c6/0x1280 fs/seq_file.c:225
>  proc_reg_read_iter+0x111/0x2d0 fs/proc/inode.c:301
>  call_read_iter include/linux/fs.h:2185 [inline]
>  new_sync_read fs/read_write.c:389 [inline]
>  vfs_read+0x67d/0x930 fs/read_write.c:470
>  ksys_read+0x127/0x250 fs/read_write.c:613
>  do_syscall_x64 arch/x86/entry/common.c:50 [inline]
>  do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
>  entry_SYSCALL_64_after_hwframe+0x63/0xcd
> RIP: 0033:0x4ae09b
> Code: e8 ea 57 fb ff eb 88 cc cc cc cc cc cc cc cc e8 fb 9b fb ff 48 8b 7c 24 10 48 8b 74 24 18 48 8b 54 24 20 48 8b 44 24 08 0f 05 <48> 3d 01 f0 ff ff 76 20 48 c7 44 24 28 ff ff ff ff 48 c7 44 24 30
> RSP: 002b:000000c0007233b8 EFLAGS: 00000212 ORIG_RAX: 0000000000000000
> RAX: ffffffffffffffda RBX: 000000c00003e800 RCX: 00000000004ae09b
> RDX: 0000000000000b49 RSI: 000000c0004fe4b7 RDI: 0000000000000003
> RBP: 000000c000723408 R08: 0000000000000001 R09: 000000c000074480
> R10: 0000000000000b49 R11: 0000000000000212 R12: 000000c000723570
> R13: 0000000000000000 R14: 000000c0000001a0 R15: 00007fe53942c2f3
>  </TASK>
> 
> 
> ---
> 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.

Let's see if the bot understands fetching patches from mailing lists:

# syz test: https://lore.kernel.org/r/20221014155845.1986223-3-ajones@xxxxxxxxxxxxxxxx

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette