[PATCH] RDMA/nldev: add check for null return from call to nlmsg_put

[Colin King]

From: Colin Ian King <colin.k...@canonical.com>

It is possible that nlmsg_put can return a null pointer, currently
this will lead to a null pointer dereference when passing a null
nlh pointer to nlmsg_end.  Fix this by adding a null pointer check.

Addresses-Coverity: ("Dereference null return value")
Fixes: cb7e0e130503 ("RDMA/core: Add interface to read device namespace sharing 
mode")
Signed-off-by: Colin Ian King <colin.k...@canonical.com>
---
 drivers/infiniband/core/nldev.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/infiniband/core/nldev.c b/drivers/infiniband/core/nldev.c
index 69188cbbd99b..4dc43b6c5a28 100644
--- a/drivers/infiniband/core/nldev.c
+++ b/drivers/infiniband/core/nldev.c
@@ -1367,6 +1367,10 @@ static int nldev_sys_get_doit(struct sk_buff *skb, 
struct nlmsghdr *nlh,
                        RDMA_NL_GET_TYPE(RDMA_NL_NLDEV,
                                         RDMA_NLDEV_CMD_SYS_GET),
                        0, 0);
+       if (!nlh) {
+               nlmsg_free(msg);
+               return -EMSGSIZE;
+       }
 
        err = nla_put_u8(msg, RDMA_NLDEV_SYS_ATTR_NETNS_MODE,
                         (u8)ib_devices_shared_netns);
-- 
2.20.1