pseries/drmem: Check for zero filled ibm, dynamic-memory property.

[Michael Ellerman]

On Fri, 2018-02-16 at 03:27:41 UTC, Nathan Fontenot wrote:
> Some versions of QEMU will produce an ibm,dynamic-reconfiguration-memory
> node with a ibm,dynamic-memory property that is zero-filled. This causes
> the drmem code to oops trying to parse this property.
> 
> The fix for this is to validate that the property does contain LMB
> entries before trying to parse it and bail if the count is zero.
> 
> Oops: Kernel access of bad area, sig: 11 [#1]
...
> 
> The ibm,dynamic-reconfiguration-memory device tree property
> generated that causes this:
> 
> ibm,dynamic-reconfiguration-memory {
>         ibm,lmb-size = <0x0 0x10000000>;
>         ibm,memory-flags-mask = <0xff>;
>         ibm,dynamic-memory = <0x0 0x0 0x0 0x0 0x0 0x0>;
>         linux,phandle = <0x7e57eed8>;
>         ibm,associativity-lookup-arrays = <0x1 0x4 0x0 0x0 0x0 0x0>;
>         ibm,memory-preservation-time = <0x0>;
> };
> 
> Signed-off-by: Nathan Fontenot <nfont at linux.vnet.ibm.com>
> Reviewed-by: Cyril Bur <cyrilbur at gmail.com>
> Tested-by: Daniel Black <daniel at linux.vnet.ibm.com>

Applied to powerpc fixes, thanks.

https://git.kernel.org/powerpc/c/2c10636a0b9c689450e85f99455839

cheers