[PATCH 5/5] powerpc/powernv: Check sysparam size before creation

[Joel Stanley <joel@jms.id.au>]

The size of the sysparam sysfs files is determined from the device tree
at boot. However the buffer is hard coded to 64 bytes. If we encounter a
parameter that is larger than 64, or miss-parse the device tree, the
buffer will overflow when reading or writing to the parameter.

Check it at discovery time, and if the parameter is too large, do not
create a sysfs entry for it.

Signed-off-by: Joel Stanley <joel@jms.id.au>
---
 arch/powerpc/platforms/powernv/opal-sysparam.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/arch/powerpc/platforms/powernv/opal-sysparam.c b/arch/powerpc/platforms/powernv/opal-sysparam.c
index 4b3367b..14231a5 100644
--- a/arch/powerpc/platforms/powernv/opal-sysparam.c
+++ b/arch/powerpc/platforms/powernv/opal-sysparam.c
@@ -241,6 +241,12 @@ void __init opal_sys_param_init(void)
 
 	/* For each of the parameters, populate the parameter attributes */
 	for (i = 0; i < count; i++) {
+		if (size[i] > MAX_PARAM_DATA_LEN) {
+			pr_warn("SYSPARAM: Not creating parameter %d as size "
+				"exceeds buffer length\n", i);
+			continue;
+		}
+
 		sysfs_attr_init(&attr[i].kobj_attr.attr);
 		attr[i].param_id = id[i];
 		attr[i].param_size = size[i];
-- 
1.9.1