Re: [PATCH v2] powerpc/64: Fix memcmp reading past the end of src/dest

On Thu, Feb 07, 2019 at 10:53:13PM +1100, Michael Ellerman wrote:

Chandan reported that fstests' generic/026 test hit a crash:

The instruction dump decodes as:
  subfic  r6,r5,8
  rlwinm  r6,r6,3,0,28
  ldbrx   r9,0,r3
  ldbrx   r10,0,r4	<-

Which shows us doing an 8 byte load from c00000062ac3fff9, which
crosses the page boundary at c00000062ac40000 and faults.

It's not OK for memcmp to read past the end of the source or
destination buffers.

It's not okay to access memory pages unsolicited.  Reading past the end
is fine per se.


Segher