elevator: fix truncation of icq_cache_name
authorEric Biggers <ebiggers@google.com>
Sat, 3 Jun 2017 03:35:51 +0000 (20:35 -0700)
committerJens Axboe <axboe@fb.com>
Tue, 6 Jun 2017 17:20:47 +0000 (11:20 -0600)
commit9bd2bbc01d17ddd567cc0f81f77fe1163e497462
tree9bdbba0442abc5693474b607a9a79c2e826d636e
parentd964f04a8fde84d978eff0d96561faa6e8de24de
elevator: fix truncation of icq_cache_name

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>
include/linux/elevator.h