[SPARC64]: Fix MD property lifetime bugs.

Property values cannot be referenced outside of
mdesc_grab()/mdesc_release() pairs.  The only major
offender was the VIO bus layer, easily fixed.

Add some commentary to mdesc.h describing these rules.

Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 25 insertions, 4 deletions

diff --git a/include/asm-sparc64/mdesc.h b/include/asm-sparc64/mdesc.h
index bbb0c0bed48..dc372df23fb 100644
--- a/include/asm-sparc64/mdesc.h
+++ b/include/asm-sparc64/mdesc.h
@@ -23,8 +23,28 @@ extern u64 mdesc_node_by_name(struct mdesc_handle *handle,
 	     (__node) != MDESC_NODE_NULL; \
 	     __node = mdesc_node_by_name(__hdl, __node, __name))
 
+/* Access to property values returned from mdesc_get_property() are
+ * only valid inside of a mdesc_grab()/mdesc_release() sequence.
+ * Once mdesc_release() is called, the memory backed up by these
+ * pointers may reference freed up memory.
+ *
+ * Therefore callers must make copies of any property values
+ * they need.
+ *
+ * These same rules apply to mdesc_node_name().
+ */
 extern const void *mdesc_get_property(struct mdesc_handle *handle,
 				      u64 node, const char *name, int *lenp);
+extern const char *mdesc_node_name(struct mdesc_handle *hp, u64 node);
+
+/* MD arc iteration, the standard sequence is:
+ *
+ *	unsigned long arc;
+ *	mdesc_for_each_arc(arc, handle, node, MDESC_ARC_TYPE_{FWD,BACK}) {
+ *		unsigned long target = mdesc_arc_target(handle, arc);
+ *		...
+ *	}
+ */
 
 #define MDESC_ARC_TYPE_FWD	"fwd"
 #define MDESC_ARC_TYPE_BACK	"back"
@@ -38,8 +58,6 @@ extern u64 mdesc_next_arc(struct mdesc_handle *handle, u64 from,
 
 extern u64 mdesc_arc_target(struct mdesc_handle *hp, u64 arc);
 
-extern const char *mdesc_node_name(struct mdesc_handle *hp, u64 node);
-
 extern void mdesc_update(void);
 
 extern void sun4v_mdesc_init(void);
diff --git a/include/asm-sparc64/vio.h b/include/asm-sparc64/vio.h
index a8a53e6fc25..83c96422e9d 100644
--- a/include/asm-sparc64/vio.h
+++ b/include/asm-sparc64/vio.h
@@ -264,12 +264,15 @@ static inline u32 vio_dring_avail(struct vio_dring_state *dr,
 		((dr->prod - dr->cons) & (ring_size - 1)));
 }
 
+#define VIO_MAX_TYPE_LEN	64
+#define VIO_MAX_COMPAT_LEN	64
+
 struct vio_dev {
 	u64			mp;
 	struct device_node	*dp;
 
-	const char		*type;
-	const char		*compat;
+	char			type[VIO_MAX_TYPE_LEN];
+	char			compat[VIO_MAX_COMPAT_LEN];
 	int			compat_len;
 
 	unsigned long		channel_id;