[PATCH] arc: validate DT CPU map strings before parsing them

[Pengpeng Hou]

arc_get_cpu_map() fetches the possible-cpus or present-cpus property
from the flat DT and immediately passes the raw pointer to
cpulist_parse(). That parser expects a NUL-terminated text buffer, but
this path does not prove that the DT property is terminated within its
declared bounds.

Reject unterminated CPU-map properties before handing them to
cpulist_parse().

Signed-off-by: Pengpeng Hou <pengpeng at iscas.ac.cn>
---
 arch/arc/kernel/smp.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/arch/arc/kernel/smp.c b/arch/arc/kernel/smp.c
index b2f2c59279a6..e0f8218e9172 100644
--- a/arch/arc/kernel/smp.c
+++ b/arch/arc/kernel/smp.c
@@ -22,6 +22,7 @@
 #include <linux/irqdomain.h>
 #include <linux/export.h>
 #include <linux/of_fdt.h>
+#include <linux/string.h>
 
 #include <asm/mach_desc.h>
 #include <asm/setup.h>
@@ -43,11 +44,15 @@ static int __init arc_get_cpu_map(const char *name, struct cpumask *cpumask)
 {
 	unsigned long dt_root = of_get_flat_dt_root();
 	const char *buf;
+	int len;
 
-	buf = of_get_flat_dt_prop(dt_root, name, NULL);
+	buf = of_get_flat_dt_prop(dt_root, name, &len);
 	if (!buf)
 		return -EINVAL;
 
+	if (!memchr(buf, '\0', len))
+		return -EINVAL;
+
 	if (cpulist_parse(buf, cpumask))
 		return -EINVAL;
 
-- 
2.50.1 (Apple Git-155)