linux-kernel - [PATCH 4.19 118/134] powerpc/pseries/energy: Use OF accessor functions to read ibm,drc-indexes

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Message-Id: <20190401170055.366596536@linuxfoundation.org>
Date:   Mon,  1 Apr 2019 19:02:34 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        "Pavithra R. Prakash" <pavrampu@...ibm.com>,
        "Gautham R. Shenoy" <ego@...ux.vnet.ibm.com>,
        Vaidyanathan Srinivasan <svaidy@...ux.vnet.ibm.com>,
        Michael Ellerman <mpe@...erman.id.au>
Subject: [PATCH 4.19 118/134] powerpc/pseries/energy: Use OF accessor functions to read ibm,drc-indexes

4.19-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Gautham R. Shenoy <ego@...ux.vnet.ibm.com>

commit ce9afe08e71e3f7d64f337a6e932e50849230fc2 upstream.

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: e83636ac3334 ("pseries/drc-info: Search DRC properties for CPU indexes")
Cc: stable@...r.kernel.org # v4.16+
Reported-by: Pavithra R. Prakash <pavrampu@...ibm.com>
Signed-off-by: Gautham R. Shenoy <ego@...ux.vnet.ibm.com>
Reviewed-by: Vaidyanathan Srinivasan <svaidy@...ux.vnet.ibm.com>
[mpe: Make the WARN_ON a WARN_ON_ONCE so it's not retriggerable]
Signed-off-by: Michael Ellerman <mpe@...erman.id.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

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

--- 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_ONCE(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;