[PATCH 4.4 100/158] elevator: fix truncation of icq_cache_name

Greg Kroah-Hartman
2019-08-02T09:33:51Z

From: Eric Biggers <ebiggers@google.com>

commit 9bd2bbc01d17ddd567cc0f81f77fe1163e497462 upstream.

gcc 7.1 reports the following warning:

block/elevator.c: In function ‘elv_register’:
block/elevator.c:898:5: warning: ‘snprintf’ output may be truncated before the last format character [-Wformat-truncation=]
"%s_io_cq", e->elevator_name);
^~~~~~~~~~
block/elevator.c:897:3: note: ‘snprintf’ output between 7 and 22 bytes into a destination of size 21
snprintf(e->icq_cache_name, sizeof(e->icq_cache_name),
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
"%s_io_cq", e->elevator_name);
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

The bug is that the name of the icq_cache is 6 characters longer than
the elevator name, but only ELV_NAME_MAX + 5 characters were reserved
for it --- so in the case of a maximum-length elevator name, the 'q'
character in "_io_cq" would be truncated by snprintf(). Fix it by
reserving ELV_NAME_MAX + 6 characters instead.

Signed-off-by: Eric Biggers <ebiggers@google.com>
Reviewed-by: Bart Van Assche <Bart.VanAssche@sandisk.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
include/linux/elevator.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/include/linux/elevator.h
+++ b/include/linux/elevator.h
@@ -97,7 +97,7 @@ struct elevator_type
struct module *elevator_owner;

/* managed by elevator core */
- char icq_cache_name[ELV_NAME_MAX + 5]; /* elvname + "_io_cq" */
+ char icq_cache_name[ELV_NAME_MAX + 6]; /* elvname + "_io_cq" */
struct list_head list;
};