[PATCH v7 1/9] net/compat: Add missing sock updates for SCM_RIGHTS

[Kees Cook]

Add missed sock updates to compat path via a new helper, which will be
used more in coming patches. (The net/core/scm.c code is left as-is here
to assist with -stable backports for the compat path.)

Cc: sta...@vger.kernel.org
Fixes: 48a87cc26c13 ("net: netprio: fd passed in SCM_RIGHTS datagram not set 
correctly")
Fixes: d84295067fc7 ("net: net_cls: fd passed in SCM_RIGHTS datagram not set 
correctly")
Signed-off-by: Kees Cook <keesc...@chromium.org>
---
 include/net/sock.h |  4 ++++
 net/compat.c       |  1 +
 net/core/sock.c    | 21 +++++++++++++++++++++
 3 files changed, 26 insertions(+)

diff --git a/include/net/sock.h b/include/net/sock.h
index c53cc42b5ab9..2be67f1ee8b1 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -890,6 +890,8 @@ static inline int sk_memalloc_socks(void)
 {
        return static_branch_unlikely(&memalloc_socks_key);
 }
+
+void __receive_sock(struct file *file);
 #else
 
 static inline int sk_memalloc_socks(void)
@@ -897,6 +899,8 @@ static inline int sk_memalloc_socks(void)
        return 0;
 }
 
+static inline void __receive_sock(struct file *file)
+{ }
 #endif
 
 static inline gfp_t sk_gfp_mask(const struct sock *sk, gfp_t gfp_mask)
diff --git a/net/compat.c b/net/compat.c
index 5e3041a2c37d..2937b816107d 100644
--- a/net/compat.c
+++ b/net/compat.c
@@ -309,6 +309,7 @@ void scm_detach_fds_compat(struct msghdr *kmsg, struct 
scm_cookie *scm)
                        break;
                }
                /* Bump the usage count and install the file. */
+               __receive_sock(fp[i]);
                fd_install(new_fd, get_file(fp[i]));
        }
 
diff --git a/net/core/sock.c b/net/core/sock.c
index 6c4acf1f0220..bde394979041 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -2840,6 +2840,27 @@ int sock_no_mmap(struct file *file, struct socket *sock, 
struct vm_area_struct *
 }
 EXPORT_SYMBOL(sock_no_mmap);
 
+/*
+ * When a file is received (via SCM_RIGHTS, etc), we must bump the
+ * various sock-based usage counts.
+ */
+void __receive_sock(struct file *file)
+{
+       struct socket *sock;
+       int error;
+
+       /*
+        * The resulting value of "error" is ignored here since we only
+        * need to take action when the file is a socket and testing
+        * "sock" for NULL is sufficient.
+        */
+       sock = sock_from_file(file, &error);
+       if (sock) {
+               sock_update_netprioidx(&sock->sk->sk_cgrp_data);
+               sock_update_classid(&sock->sk->sk_cgrp_data);
+       }
+}
+
 ssize_t sock_no_sendpage(struct socket *sock, struct page *page, int offset, 
size_t size, int flags)
 {
        ssize_t res;
-- 
2.25.1