In preparation to enabling -Wvla, remove the use of stack VLA. In this particular case, variable buf_size is replaced with a constant expression that can be computed at preprocessing time. This avoids two VLA warnings. Also, as a consequence of the mentioned change, some code was slightly refactored. The use of stack Variable Length Arrays needs to be avoided, as they can be a vector for stack exhaustion, which can be both a runtime bug or a security flaw. Also, in general, as code evolves it is easy to lose track of how big a VLA can get. Thus, we can end up having runtime failures that are hard to debug. Also, fixed as part of the directive to remove all VLAs from the kernel: https://lkml.org/lkml/2018/3/7/621 Signed-off-by: Gustavo A. R. Silva <gustavo@xxxxxxxxxxxxxx> --- drivers/block/rbd.c | 15 +++++++-------- 1 file changed, 7 insertions(+), 8 deletions(-) diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c index 1e03b04..5133122 100644 --- a/drivers/block/rbd.c +++ b/drivers/block/rbd.c @@ -3091,20 +3091,20 @@ static int __rbd_notify_op_lock(struct rbd_device *rbd_dev, { struct ceph_osd_client *osdc = &rbd_dev->rbd_client->client->osdc; struct rbd_client_id cid = rbd_get_cid(rbd_dev); - int buf_size = 4 + 8 + 8 + CEPH_ENCODING_START_BLK_LEN; - char buf[buf_size]; + char buf[4 + 8 + 8 + CEPH_ENCODING_START_BLK_LEN]; void *p = buf; dout("%s rbd_dev %p notify_op %d\n", __func__, rbd_dev, notify_op); /* encode *LockPayload NotifyMessage (op + ClientId) */ - ceph_start_encoding(&p, 2, 1, buf_size - CEPH_ENCODING_START_BLK_LEN); + ceph_start_encoding(&p, 2, 1, + sizeof(buf) - CEPH_ENCODING_START_BLK_LEN); ceph_encode_32(&p, notify_op); ceph_encode_64(&p, cid.gid); ceph_encode_64(&p, cid.handle); return ceph_osdc_notify(osdc, &rbd_dev->header_oid, - &rbd_dev->header_oloc, buf, buf_size, + &rbd_dev->header_oloc, buf, sizeof(buf), RBD_NOTIFY_TIMEOUT, preply_pages, preply_len); } @@ -3610,19 +3610,18 @@ static void __rbd_acknowledge_notify(struct rbd_device *rbd_dev, u64 notify_id, u64 cookie, s32 *result) { struct ceph_osd_client *osdc = &rbd_dev->rbd_client->client->osdc; - int buf_size = 4 + CEPH_ENCODING_START_BLK_LEN; - char buf[buf_size]; + char buf[4 + CEPH_ENCODING_START_BLK_LEN]; + int buf_size = 0; int ret; if (result) { void *p = buf; + buf_size = sizeof(buf); /* encode ResponseMessage */ ceph_start_encoding(&p, 1, 1, buf_size - CEPH_ENCODING_START_BLK_LEN); ceph_encode_32(&p, *result); - } else { - buf_size = 0; } ret = ceph_osdc_notify_ack(osdc, &rbd_dev->header_oid, -- 2.7.4
