* Gautham R Shenoy ego@linux.vnet.ibm.com [2019-03-08 21:03:24]:

From: "Gautham R. Shenoy" ego@linux.vnet.ibm.com

In cpu_to_drc_index() in the case when FW_FEATURE_DRC_INFO is absent, we currently use of_read_property() to obtain the pointer to the array corresponding to the property "ibm,drc-indexes". The elements of this array are of type __be32, but are accessed without any conversion to the OS-endianness, which is buggy on a Little Endian OS.

Fix this by using of_property_read_u32_index() accessor function to safely read the elements of the array.

Fixes: commit e83636ac3334 ("pseries/drc-info: Search DRC properties for CPU indexes") Cc: stable@vger.kernel.org #v4.16+ Reported-by: Pavithra R. Prakash pavrampu@in.ibm.com Signed-off-by: Gautham R. Shenoy ego@linux.vnet.ibm.com

Reviewed-by: Vaidyanathan Srinivasan svaidy@linux.vnet.ibm.com

---

arch/powerpc/platforms/pseries/pseries_energy.c | 27 ++++++++++++++++--------- 1 file changed, 18 insertions(+), 9 deletions(-)

diff --git a/arch/powerpc/platforms/pseries/pseries_energy.c b/arch/powerpc/platforms/pseries/pseries_energy.c index 6ed2212..1c4d1ba 100644 --- a/arch/powerpc/platforms/pseries/pseries_energy.c +++ b/arch/powerpc/platforms/pseries/pseries_energy.c @@ -77,18 +77,27 @@ static u32 cpu_to_drc_index(int cpu)

ret = drc.drc_index_start + (thread_index * drc.sequential_inc);

} else {

• const __be32 *indexes;
  

• indexes = of_get_property(dn, "ibm,drc-indexes", NULL);
  

• if (indexes == NULL)
  

• 	goto err_of_node_put;
  

• u32 nr_drc_indexes, thread_drc_index;
  
  

  /*

•  * The first element indexes[0] is the number of drc_indexes
  

•  * returned in the list.  Hence thread_index+1 will get the
  

•  * drc_index corresponding to core number thread_index.
  

•  * The first element of ibm,drc-indexes array is the
  

•  * number of drc_indexes returned in the list.  Hence
  

•  * thread_index+1 will get the drc_index corresponding
  

•  * to core number thread_index.
  

  */

• ret = indexes[thread_index + 1];
  

• rc = of_property_read_u32_index(dn, "ibm,drc-indexes",
  

• 				0, &nr_drc_indexes);
  

• if (rc)
  

• 	goto err_of_node_put;
  

• WARN_ON(thread_index > nr_drc_indexes);
  

• rc = of_property_read_u32_index(dn, "ibm,drc-indexes",
  

• 				thread_index + 1,
  

• 				&thread_drc_index);
  

• if (rc)
  

• 	goto err_of_node_put;
  

• ret = thread_drc_index;
  

Oops! Good bugfix. We should use device tree accessors like this in all places for correct and safe code.

Thanks!

--Vaidy