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From:   "Gautham R. Shenoy" <ego@linux.vnet.ibm.com>
To:     Michael Bringmann <mwb@linux.vnet.ibm.com>,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Paul Mackerras <paulus@samba.org>,
        Michael Ellerman <mpe@ellerman.id.au>,
        Vaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com>
Cc:     linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org,
        "Pavithra R. Prakash" <pavrampu@in.ibm.com>,
        "Gautham R. Shenoy" <ego@linux.vnet.ibm.com>,
        <stable@vger.kernel.org>
Subject: [PATCH] pseries/energy: Use OF accessor functions to read ibm,drc-indexes
Date:   Fri,  8 Mar 2019 21:03:24 +0530
Message-Id: <1552059204-18626-1-git-send-email-ego@linux.vnet.ibm.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

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>
---
 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;
 	}
 
 	rc = 0;
-- 
1.9.4