23.06.2020 00:03, Eric Blake wrote:
> When snprintf returns the same value as the buffer size, the final
> byte was truncated to ensure a NUL terminator. Fortunately, such long
> export names are unusual enough, with no real impact other than what
> is displayed to the user.
>
> Fixes: 5c86bdf12089
Oh, I remember myself checking snprintf spec when reviewing this, but
still I missed this thing :(
> Reported-by: Max Reitz <mreitz@redhat.com>
> Signed-off-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
> ---
> block/nbd.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/block/nbd.c b/block/nbd.c
> index eed160c5cda1..8301fcac0589 100644
> --- a/block/nbd.c
> +++ b/block/nbd.c
> @@ -2009,7 +2009,7 @@ static void nbd_refresh_filename(BlockDriverState *bs)
> len = snprintf(bs->exact_filename, sizeof(bs->exact_filename),
> "nbd://%s:%s", host, port);
> }
> - if (len > sizeof(bs->exact_filename)) {
> + if (len >= sizeof(bs->exact_filename)) {
> /* Name is too long to represent exactly, so leave it empty. */
> bs->exact_filename[0] = '\0';
> }
>
Hmm, interesting, that in case of len=0 (no one branch was executed from previous
if-else-if, which seems possible) we do nothing. Shouldn't this if actually be
if (!len || len >= sizeof(bs->exact_filename)) {
/* Name is too long or we have nothing to report */
bs->exact_filename[0] = '\0';
}
Probably not, as bdrv_refresh_filename() does it anyway prior to calling drv->bdrv_refresh_filename().
--
Best regards,
Vladimir