Re: BUG: unable to handle kernel NULL pointer dereference in rcu_core

[Zhouyi Zhou]

Hi

On Mon, Feb 27, 2023 at 2:30 PM Sanan Hasanov
<sanan.hasanov@xxxxxxxxxxxxxxx> wrote:
>
> Good day, dear maintainers,
>
> We found a bug using a modified kernel configuration file used by syzbot.
>
> We enhanced the coverage of the configuration file using our tool, klocalizer.
>
> Kernel Branch: 6.2.0-next-20230221
> Kernel config: https://drive.google.com/file/d/1QKAQV11zjOwISifUc-skRBoTo3EXhutY/view?usp=share_link
> C Reproducer: Unfortunately, there is no reproducer yet.
I downloaded 6.2.0-next-20230221 (wget
https://kernel.source.codeaurora.cn/pub/scm/linux/kernel/git/next/linux-next.git/snapshot/linux-next-next-20230221.tar.gz)
and compile the kernel using above kernel config, and started syzkaller:
http://154.220.3.120:56700/

Hope I can reproduce the bug and chase down the cause of the bug.

You are welcome ;-)
Thanks
Zhouyi
>
> Thank you!
>
> Best regards,
> Sanan Hasanov
>
> BUG: kernel NULL pointer dereference, address: 0000000000000000
> #PF: supervisor instruction fetch in kernel mode
> #PF: error_code(0x0010) - not-present page
> PGD 53756067 P4D 53756067 PUD 0
> Oops: 0010 [#1] PREEMPT SMP KASAN
> CPU: 7 PID: 0 Comm: swapper/7 Not tainted 6.2.0-next-20230221 #1
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014
> RIP: 0010:0x0
> Code: Unable to access opcode bytes at 0xffffffffffffffd6.
> RSP: 0018:ffffc900003f8e48 EFLAGS: 00010246
> RAX: 0000000000000000 RBX: ffff888100833900 RCX: 00000000b9582f6c
> RDX: 1ffff11020106853 RSI: ffffffff816b2769 RDI: ffff888043f64708
> RBP: 000000000000000c R08: 0000000000000000 R09: ffffffff900b895f
> R10: fffffbfff201712b R11: 000000000008e001 R12: dffffc0000000000
> R13: ffffc900003f8ec8 R14: ffff888043f64708 R15: 000000000000000b
> FS:  0000000000000000(0000) GS:ffff888119f80000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: ffffffffffffffd6 CR3: 0000000054e64000 CR4: 0000000000350ee0
> Call Trace:
>  <IRQ>
>  rcu_core+0x85d/0x1960
>  __do_softirq+0x2e5/0xae2
>  __irq_exit_rcu+0x11d/0x190
>  irq_exit_rcu+0x9/0x20
>  sysvec_apic_timer_interrupt+0x97/0xc0
>  </IRQ>
>  <TASK>
>  asm_sysvec_apic_timer_interrupt+0x1a/0x20
> RIP: 0010:default_idle+0xf/0x20
> Code: 89 07 49 c7 c0 08 00 00 00 4d 29 c8 4c 01 c7 4c 29 c2 e9 76 ff ff ff cc cc cc cc f3 0f 1e fa eb 07 0f 00 2d e3 8a 34 00 fb f4 <fa> c3 66 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 f3 0f 1e fa 65
> RSP: 0018:ffffc9000017fe00 EFLAGS: 00000202
> RAX: 0000000000dfbea1 RBX: dffffc0000000000 RCX: ffffffff89b1da9c
> RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000000
> RBP: 0000000000000007 R08: 0000000000000001 R09: ffff888119fb6c23
> R10: ffffed10233f6d84 R11: dffffc0000000000 R12: 0000000000000003
> R13: ffff888100833900 R14: ffffffff8e112850 R15: 0000000000000000
>  default_idle_call+0x67/0xa0
>  do_idle+0x361/0x440
>  cpu_startup_entry+0x18/0x20
>  start_secondary+0x256/0x300
>  secondary_startup_64_no_verify+0xce/0xdb
>  </TASK>
> Modules linked in:
> CR2: 0000000000000000
> ---[ end trace 0000000000000000 ]---
> RIP: 0010:0x0
> Code: Unable to access opcode bytes at 0xffffffffffffffd6.
> RSP: 0018:ffffc900003f8e48 EFLAGS: 00010246
>
> RAX: 0000000000000000 RBX: ffff888100833900 RCX: 00000000b9582f6c
> RDX: 1ffff11020106853 RSI: ffffffff816b2769 RDI: ffff888043f64708
> RBP: 000000000000000c R08: 0000000000000000 R09: ffffffff900b895f
> R10: fffffbfff201712b R11: 000000000008e001 R12: dffffc0000000000
> R13: ffffc900003f8ec8 R14: ffff888043f64708 R15: 000000000000000b
> FS:  0000000000000000(0000) GS:ffff888119f80000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: ffffffffffffffd6 CR3: 0000000054e64000 CR4: 0000000000350ee0
> ----------------
> Code disassembly (best guess):
>    0:   89 07                   mov    %eax,(%rdi)
>    2:   49 c7 c0 08 00 00 00    mov    $0x8,%r8
>    9:   4d 29 c8                sub    %r9,%r8
>    c:   4c 01 c7                add    %r8,%rdi
>    f:   4c 29 c2                sub    %r8,%rdx
>   12:   e9 76 ff ff ff          jmp    0xffffff8d
>   17:   cc                      int3
>   18:   cc                      int3
>   19:   cc                      int3
>   1a:   cc                      int3
>   1b:   f3 0f 1e fa             endbr64
>   1f:   eb 07                   jmp    0x28
>   21:   0f 00 2d e3 8a 34 00    verw   0x348ae3(%rip)        # 0x348b0b
>   28:   fb                      sti
>   29:   f4                      hlt
> * 2a:   fa                      cli <-- trapping instruction
>   2b:   c3                      ret
>   2c:   66 66 2e 0f 1f 84 00    data16 cs nopw 0x0(%rax,%rax,1)
>   33:   00 00 00 00
>   37:   0f 1f 40 00             nopl   0x0(%rax)
>   3b:   f3 0f 1e fa             endbr64
>   3f:   65                      gs
>