net, sk_msg: Don't use RCU_INIT_POINTER on sk_user_data

sparse reports an error due to use of RCU_INIT_POINTER helper to assign to
sk_user_data pointer, which is not tagged with __rcu:

net/core/sock.c:1875:25: error: incompatible types in comparison expression (different address spaces):
net/core/sock.c:1875:25:    void [noderef] <asn:4> *
net/core/sock.c:1875:25:    void *

... and rightfully so. sk_user_data is not always treated as a pointer to
an RCU-protected data. When it is used to point at an RCU-protected object,
we access it with __sk_user_data to inform sparse about it.

In this case, when the child socket does not inherit sk_user_data from the
parent, there is no reason to treat it as an RCU-protected pointer.

Use a regular assignment to clear the pointer value.

Fixes: f1ff5ce2cd5e ("net, sk_msg: Clear sk_user_data pointer on clone if tagged")
Reported-by: kbuild test robot <lkp@intel.com>
Signed-off-by: Jakub Sitnicki <jakub@cloudflare.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20200402125524.851439-1-jakub@cloudflare.com

diff --git a/net/core/sock.c b/net/core/sock.c
index da32d9b6d09f86172ba5e40a1fdd053d505ec445..0510826bf8609706da2444dbfdc273d0494b6dc9 100644 (file)
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -1872,7 +1872,7 @@ struct sock *sk_clone_lock(const struct sock *sk, const gfp_t priority)
                 * as not suitable for copying when cloning.
                 */
                if (sk_user_data_is_nocopy(newsk))
-                       RCU_INIT_POINTER(newsk->sk_user_data, NULL);
+                       newsk->sk_user_data = NULL;
 
                newsk->sk_err      = 0;
                newsk->sk_err_soft = 0;