linux-kernel - [PATCH v7 1/9] net/compat: Add missing sock updates for SCM

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Date:   Thu,  9 Jul 2020 11:26:34 -0700
From:   Kees Cook <keescook@...omium.org>
To:     linux-kernel@...r.kernel.org
Cc:     Kees Cook <keescook@...omium.org>, stable@...r.kernel.org,
        Sargun Dhillon <sargun@...gun.me>,
        Christian Brauner <christian@...uner.io>,
        Tycho Andersen <tycho@...ho.ws>,
        David Laight <David.Laight@...LAB.COM>,
        Christoph Hellwig <hch@....de>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Aleksa Sarai <cyphar@...har.com>,
        Matt Denton <mpdenton@...gle.com>,
        Jann Horn <jannh@...gle.com>, Chris Palmer <palmer@...gle.com>,
        Robert Sesek <rsesek@...gle.com>,
        Giuseppe Scrivano <gscrivan@...hat.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Andy Lutomirski <luto@...capital.net>,
        Will Drewry <wad@...omium.org>, Shuah Khan <shuah@...nel.org>,
        netdev@...r.kernel.org, containers@...ts.linux-foundation.org,
        linux-api@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-kselftest@...r.kernel.org
Subject: [PATCH v7 1/9] net/compat: Add missing sock updates for SCM_RIGHTS

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: stable@...r.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 <keescook@...omium.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