[PATCH 4.16 19/52] RDMA/ucma: Allow resolving address w/o specifying source address

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

4.16-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Roland Dreier <roland@purestorage.com>

commit 09abfe7b5b2f442a85f4c4d59ecf582ad76088d7 upstream.

The RDMA CM will select a source device and address by consulting
the routing table if no source address is passed into
rdma_resolve_address().  Userspace will ask for this by passing an
all-zero source address in the RESOLVE_IP command.  Unfortunately
the new check for non-zero address size rejects this with EINVAL,
which breaks valid userspace applications.

Fix this by explicitly allowing a zero address family for the source.

Fixes: 2975d5de6428 ("RDMA/ucma: Check AF family prior resolving address")
Cc: <stable@vger.kernel.org>
Signed-off-by: Roland Dreier <roland@purestorage.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/infiniband/core/ucma.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/infiniband/core/ucma.c
+++ b/drivers/infiniband/core/ucma.c
@@ -678,7 +678,7 @@ static ssize_t ucma_resolve_ip(struct uc
 	if (copy_from_user(&cmd, inbuf, sizeof(cmd)))
 		return -EFAULT;
 
-	if (!rdma_addr_size_in6(&cmd.src_addr) ||
+	if ((cmd.src_addr.sin6_family && !rdma_addr_size_in6(&cmd.src_addr)) ||
 	    !rdma_addr_size_in6(&cmd.dst_addr))
 		return -EINVAL;