[BLOCK] fix string handling in elv_iosched_store
elv_iosched_store doesn't terminate string passed from userspace if
it's too long. Also, if the written length is zero (probably not
possible), it accesses elevator_name[-1]. This patch fixes both bugs.
Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Jens Axboe <axboe@suse.de>
diff --git a/block/elevator.c b/block/elevator.c
index 73aa46b..cacfff7 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -762,13 +762,15 @@
ssize_t elv_iosched_store(request_queue_t *q, const char *name, size_t count)
{
char elevator_name[ELV_NAME_MAX];
+ size_t len;
struct elevator_type *e;
- memset(elevator_name, 0, sizeof(elevator_name));
- strncpy(elevator_name, name, sizeof(elevator_name));
+ elevator_name[sizeof(elevator_name) - 1] = '\0';
+ strncpy(elevator_name, name, sizeof(elevator_name) - 1);
+ len = strlen(elevator_name);
- if (elevator_name[strlen(elevator_name) - 1] == '\n')
- elevator_name[strlen(elevator_name) - 1] = '\0';
+ if (len && elevator_name[len - 1] == '\n')
+ elevator_name[len - 1] = '\0';
e = elevator_get(elevator_name);
if (!e) {