linux-kernel - [PATCH 3.12 44/84] ARM: 8616/1: dt: Respect property size when parsing CPUs

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Date:   Mon, 17 Oct 2016 09:51:31 +0200
From:   Jiri Slaby <jslaby@...e.cz>
To:     stable@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, Robin Murphy <robin.murphy@....com>,
        Russell King <linux@...linux.org.uk>,
        Russell King <rmk+kernel@....linux.org.uk>,
        Jiri Slaby <jslaby@...e.cz>
Subject: [PATCH 3.12 44/84] ARM: 8616/1: dt: Respect property size when parsing CPUs

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

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

===============

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@...linux.org.uk>
Signed-off-by: Robin Murphy <robin.murphy@....com>
Signed-off-by: Russell King <rmk+kernel@....linux.org.uk>
Signed-off-by: Jiri Slaby <jslaby@...e.cz>
---
 arch/arm/kernel/devtree.c | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/arch/arm/kernel/devtree.c b/arch/arm/kernel/devtree.c
index 41960fb0daff..68ff9e6473be 100644
--- a/arch/arm/kernel/devtree.c
+++ b/arch/arm/kernel/devtree.c
@@ -90,6 +90,8 @@ 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"))
@@ -101,17 +103,23 @@ 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);
 			return;
 		}
 
 		/*
-		 * 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))
 			return;
 
 		/*
-- 
2.10.1