[for-next][PATCH 4/5] tracing: Handle tracing_map_alloc_elts() error path correctly

[Steven Rostedt]

From: Tom Zanussi <tom.zanussi@xxxxxxxxxxxxxxx>

If tracing_map_elt_alloc() fails, it will return ERR_PTR() instead of
NULL, so change the check to IS_ERROR().  We also need to set the
failed entry in the map->elts array to NULL instead of ERR_PTR() so
tracing_map_free_elts() doesn't try freeing an ERR_PTR().

tracing_map_free_elts() should also zero out what it frees so a
reentrant call won't find previously freed elements.

Link: http://lkml.kernel.org/r/f29d03b00bce3aac8cf151a8a30e6c83e5fee66d.1461610073.git.tom.zanussi@xxxxxxxxxxxxxxx

Signed-off-by: Tom Zanussi <tom.zanussi@xxxxxxxxxxxxxxx>
Signed-off-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
---
 kernel/trace/tracing_map.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/kernel/trace/tracing_map.c b/kernel/trace/tracing_map.c
index e7dfc5eec669..0a689bbb78ef 100644
--- a/kernel/trace/tracing_map.c
+++ b/kernel/trace/tracing_map.c
@@ -366,10 +366,13 @@ static void tracing_map_free_elts(struct tracing_map *map)
 	if (!map->elts)
 		return;
 
-	for (i = 0; i < map->max_elts; i++)
+	for (i = 0; i < map->max_elts; i++) {
 		tracing_map_elt_free(*(TRACING_MAP_ELT(map->elts, i)));
+		*(TRACING_MAP_ELT(map->elts, i)) = NULL;
+	}
 
 	tracing_map_array_free(map->elts);
+	map->elts = NULL;
 }
 
 static int tracing_map_alloc_elts(struct tracing_map *map)
@@ -383,7 +386,8 @@ static int tracing_map_alloc_elts(struct tracing_map *map)
 
 	for (i = 0; i < map->max_elts; i++) {
 		*(TRACING_MAP_ELT(map->elts, i)) = tracing_map_elt_alloc(map);
-		if (!(*(TRACING_MAP_ELT(map->elts, i)))) {
+		if (IS_ERR(*(TRACING_MAP_ELT(map->elts, i)))) {
+			*(TRACING_MAP_ELT(map->elts, i)) = NULL;
 			tracing_map_free_elts(map);
 
 			return -ENOMEM;
-- 
2.8.0.rc3