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SubjectRe: [lkp-robot] [net] 98cd1552ea: BUG:unable_to_handle_kernel
On Sun, Aug 13, 2017 at 11:10 PM, kernel test robot
<xiaolong.ye@intel.com> wrote:
> FYI, we noticed the following commit:
>
> commit: 98cd1552ea27e512c7e99e2aa76042a26e4fb25c ("net: dsa: Mock-up driver")
> https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git master
>
> in testcase: trinity
> with following parameters:
>
> runtime: 300s
>
> test-description: Trinity is a linux system call fuzz tester.
> test-url: http://codemonkey.org.uk/projects/trinity/
>
> on test machine: qemu-system-x86_64 -enable-kvm -cpu host -smp 2 -m 1G
>
> caused below changes (please refer to attached dmesg/kmsg for entire log/backtrace):
>
> +-----------------------------------------------------+------------+------------+
> | | 772c3bdad1 | 98cd1552ea |
> +-----------------------------------------------------+------------+------------+
> | boot_successes | 0 | 0 |
> | boot_failures | 30 | 30 |
> | WARNING:at_arch/x86/mm/dump_pagetables.c:#note_page | 30 | 30 |
> | invoked_oom-killer:gfp_mask=0x | 28 | 13 |
> | Mem-Info | 28 | 13 |
> | Out_of_memory:Kill_process | 28 | 13 |
> | BUG:unable_to_handle_kernel | 0 | 16 |
> | Oops:#[##] | 0 | 16 |
> | Kernel_panic-not_syncing:Fatal_exception | 0 | 16 |
> +-----------------------------------------------------+------------+------------+
>
> [ 9.603869] BUG: unable to handle kernel NULL pointer dereference at 00000000000001f0\

The code disassembly is

0: 55 push %rbp
1: 48 89 e5 mov %rsp,%rbp
4: 41 55 push %r13
6: 41 54 push %r12
8: 41 89 f4 mov %esi,%r12d
b: 53 push %rbx
c: 48 8b 87 10 03 00 00 mov 0x310(%rdi),%rax
13: 31 db xor %ebx,%ebx
15:* 4c 8b a8 f0 01 00 00 mov 0x1f0(%rax),%r13 <--
trapping instruction

which seems to be

struct dsa_switch_tree *dst = dev->dsa_ptr;
struct dsa_port *cpu_dp = dsa_get_cpu_port(dst);

where 'dst' is NULL (the "dsa_get_cpu_port() function is just an
inline that returns "dst->cpu_dp").

So 'dev' is not NULL, but dev->dsa_ptr definitely is.

Linus

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