Re: [linux-next][Oops] CPU toggle resulted in kernel crash

[Michael Ellerman]

Kees Cook <keescook@xxxxxxxxxxxx> writes:

> On Thu, Oct 5, 2017 at 10:21 AM, Abdul Haleem
> <abdhalee@xxxxxxxxxxxxxxxxxx> wrote:
>> Hi,
>>
>> CPU off on in a loop for single cpu results in kernel panic for
>> 4.14.0-rc2-next-20170929
>>
>> Machine: Power 8 PowerVM LPAR
>> Kernel: 4.14.0-rc2-next-20170929
>> gcc: 5.1.1
>> config : attached
>>
>> Steps to recreate:
>> -----------------
>> The issue is not reproducible all the time.
>>
>> The trace occurred when CPU toggle operation for cpu14 in a loop for 10
>> iterations.
>>
>> the Faulting instruction address: 0xc00000000035465c
>> maps to:
>>
>> 0xc00000000035465c is in deactivate_slab (mm/slub.c:261).
>> 256
>> 257     /* Returns the freelist pointer recorded at location ptr_addr. */
>> 258     static inline void *freelist_dereference(const struct kmem_cache *s,
>> 259                                              void *ptr_addr)
>> 260     {
>> 261             return freelist_ptr(s, (void *)*(unsigned long *)(ptr_addr),
>> 262                                 (unsigned long)ptr_addr);
>> 263     }
>> 264
>> 265     static inline void *get_freepointer(struct kmem_cache *s, void *object)
>
> This looks like slub cache corruption (a NULL pointer dereference for
> the heap freelist).

Abdul, try turning on CONFIG_SLUB_DEBUG, and booting with slub_debug=FZP
on the command line.

cheers