On Fri, Mar 30, 2018 at 9:17 PM, Gustavo A. R. Silva <gustavo@xxxxxxxxxxxxxx> wrote: > 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, Already fixed: https://github.com/ceph/ceph-client/commit/2474e77e75215a3cad3b652d2f55ba5b123cb119 Thanks, Ilya
