Re: [powerpc/powervm]Oops: Kernel access of bad area, sig: 11 [#1] while running stress-ng

vrbagal1 [off-list ref] writes:

On 2018-07-10 13:37, Nicholas Piggin wrote:

quoted

On Tue, 10 Jul 2018 11:58:40 +0530
vrbagal1 [off-list ref] wrote:

quoted

Hi,

Observing kernel oops on Power9(ZZ) box, running on PowerVM, while
running stress-ng.


Kernel: 4.18.0-rc4
Machine: Power9 ZZ (PowerVM)
Test: Stress-ng

Attached is .config file

Traces:

  [12251.245209] Oops: Kernel access of bad area, sig: 11 [#1]

Can you post the lines above this? Otherwise we don't know what address
it tried to access (without decoding the instructions and 
reconstructing
it from registers at least, which the XFS devs wouldn't be inclined to
do).

ah my bad.

  [12251.245179] Unable to handle kernel paging request for data at address 0x6000000060000000
  [12251.245199] Faulting instruction address: 0xc000000000319e2c

Which matches the regs & disassembly:

r4 = 6000000060000000 
r9 = 0
ldx     r9,r4,r9	<- pop

So object was 0x6000000060000000.

That looks like two nops, ie. we got some code?

And there's only one caller of prefetch_freepointer() in slab_alloc_node():

	prefetch_freepointer(s, next_object);


So slab corruption is looking likely.

Do you have slub_debug=FZP on the kernel command line?

cheers