Patch "ARM: 8616/1: dt: Respect property size when parsing CPUs" has been added to the 4.4-stable tree

[<gregkh@linuxfoundation.org>]

This is a note to let you know that I've just added the patch titled

    ARM: 8616/1: dt: Respect property size when parsing CPUs

to the 4.4-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     arm-8616-1-dt-respect-property-size-when-parsing-cpus.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From ba6dea4f7cedb4b1c17e36f4087675d817c2e24b Mon Sep 17 00:00:00 2001
From: Robin Murphy <robin.murphy@arm.com>
Date: Mon, 26 Sep 2016 16:50:55 +0100
Subject: ARM: 8616/1: dt: Respect property size when parsing CPUs

From: Robin Murphy <robin.murphy@arm.com>

commit ba6dea4f7cedb4b1c17e36f4087675d817c2e24b upstream.

Whilst MPIDR values themselves are less than 32 bits, it is still
perfectly valid for a DT to have #address-cells > 1 in the CPUs node,
resulting in the "reg" property having leading zero cell(s). In that
situation, the big-endian nature of the data conspires with the current
behaviour of only reading the first cell to cause the kernel to think
all CPUs have ID 0, and become resoundingly unhappy as a consequence.

Take the full property length into account when parsing CPUs so as to
be correct under any circumstances.

Cc: Russell King <linux@armlinux.org.uk>
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 arch/arm/kernel/devtree.c |   14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

--- a/arch/arm/kernel/devtree.c
+++ b/arch/arm/kernel/devtree.c
@@ -87,6 +87,8 @@ void __init arm_dt_init_cpu_maps(void)
 		return;
 
 	for_each_child_of_node(cpus, cpu) {
+		const __be32 *cell;
+		int prop_bytes;
 		u32 hwid;
 
 		if (of_node_cmp(cpu->type, "cpu"))
@@ -98,7 +100,8 @@ void __init arm_dt_init_cpu_maps(void)
 		 * properties is considered invalid to build the
 		 * cpu_logical_map.
 		 */
-		if (of_property_read_u32(cpu, "reg", &hwid)) {
+		cell = of_get_property(cpu, "reg", &prop_bytes);
+		if (!cell || prop_bytes < sizeof(*cell)) {
 			pr_debug(" * %s missing reg property\n",
 				     cpu->full_name);
 			of_node_put(cpu);
@@ -106,10 +109,15 @@ void __init arm_dt_init_cpu_maps(void)
 		}
 
 		/*
-		 * 8 MSBs must be set to 0 in the DT since the reg property
+		 * Bits n:24 must be set to 0 in the DT since the reg property
 		 * defines the MPIDR[23:0].
 		 */
-		if (hwid & ~MPIDR_HWID_BITMASK) {
+		do {
+			hwid = be32_to_cpu(*cell++);
+			prop_bytes -= sizeof(*cell);
+		} while (!hwid && prop_bytes > 0);
+
+		if (prop_bytes || (hwid & ~MPIDR_HWID_BITMASK)) {
 			of_node_put(cpu);
 			return;
 		}


Patches currently in stable-queue which might be from robin.murphy@arm.com are

queue-4.4/arm-8616-1-dt-respect-property-size-when-parsing-cpus.patch