RDS: Copy rds_iovecs into kernel memory instead of rereading from userspace
Change rds_rdma_pages to take a passed-in rds_iovec array instead of doing copy_from_user itself. Change rds_cmsg_rdma_args to copy rds_iovec array once only. This eliminates the possibility of userspace changing it after our sanity checks. Implement stack-based storage for small numbers of iovecs, based on net/socket.c, to save an alloc in the extremely common case. Although this patch reduces iovec copies in cmsg_rdma_args to 1, we still do another one in rds_rdma_extra_size. Getting rid of that one will be trickier, so it'll be a separate patch. Signed-off-by: NAndy Grover <andy.grover@oracle.com> Signed-off-by: NDavid S. Miller <davem@davemloft.net>
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