crypto: user - make NETLINK_CRYPTO work inside netns

Currently, NETLINK_CRYPTO works only in the init network namespace. It
doesn't make much sense to cut it out of the other network namespaces,
so do the minor plumbing work necessary to make it work in any network
namespace. Code inspired by net/core/sock_diag.c.

Tested using kcapi-dgst from libkcapi [1]:
Before:
    # unshare -n kcapi-dgst -c sha256 </dev/null | wc -c
    libkcapi - Error: Netlink error: sendmsg failed
    libkcapi - Error: Netlink error: sendmsg failed
    libkcapi - Error: NETLINK_CRYPTO: cannot obtain cipher information for hmac(sha512) (is required crypto_user.c patch missing? see documentation)
    0

After:
    # unshare -n kcapi-dgst -c sha256 </dev/null | wc -c
    32

[1] https://github.com/smuellerDD/libkcapi

Signed-off-by: Ondrej Mosnacek <omosnace@redhat.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

1 files changed, 3 insertions, 0 deletions

diff --git a/include/net/net_namespace.h b/include/net/net_namespace.h
index 4a9da951a794..85bc1de5dece 100644
--- a/include/net/net_namespace.h
+++ b/include/net/net_namespace.h
@@ -171,6 +171,9 @@ struct net {
 #ifdef CONFIG_XDP_SOCKETS
 	struct netns_xdp	xdp;
 #endif
+#if IS_ENABLED(CONFIG_CRYPTO_USER)
+	struct sock		*crypto_nlsk;
+#endif
 	struct sock		*diag_nlsk;
 	atomic_t		fnhe_genid;
 } __randomize_layout;