tree a1194d334760f049164a46ceac026e5628f1a2b0
parent 738459e3f88538f2ece263424dafe5d91799e46b
author Greg Kurz <gkurz@linux.vnet.ibm.com> 1414738211 +0100
committer Herbert Xu <herbert@gondor.apana.org.au> 1415286622 +0800

hwrng: pseries - port to new read API and fix stack corruption

The add_early_randomness() function in drivers/char/hw_random/core.c passes
a 16-byte buffer to pseries_rng_data_read(). Unfortunately, plpar_hcall()
returns four 64-bit values and trashes 16 bytes on the stack.

This bug has been lying around for a long time. It got unveiled by:

commit d3cc7996473a7bdd33256029988ea690754e4e2a
Author: Amit Shah <amit.shah@redhat.com>
Date:   Thu Jul 10 15:42:34 2014 +0530

    hwrng: fetch randomness only after device init

It may trig a oops while loading or unloading the pseries-rng module for both
PowerVM and PowerKVM guests.

This patch does two things:
- pass an intermediate well sized buffer to plpar_hcall(). This is acceptalbe
  since we're not on a hot path.
- move to the new read API so that we know the return buffer size for sure.

Cc: stable@vger.kernel.org
Signed-off-by: Greg Kurz <gkurz@linux.vnet.ibm.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>