Merge branch 'af_unix-fix-a-null-deref-in-sk_diag_dump_uid'

Kuniyuki Iwashima says:

====================
af_unix: Fix a NULL deref in sk_diag_dump_uid().

The first patch fixes a NULL deref when we dump a AF_UNIX socket's UID,
and the second patch adds a repro/test for such a case.
====================

Link: https://lore.kernel.org/r/20221127012412.37969-1-kuniyu@amazon.comSigned-off-by: Paolo Abeni <pabeni@redhat.com>

net/unix/diag.c

@@ -114,14 +114,16 @@ static int sk_diag_show_rqlen(struct sock *sk, struct sk_buff *nlskb)
 	return nla_put(nlskb, UNIX_DIAG_RQLEN, sizeof(rql), &rql);
 }
 
-static int sk_diag_dump_uid(struct sock *sk, struct sk_buff *nlskb)
+static int sk_diag_dump_uid(struct sock *sk, struct sk_buff *nlskb,
+			    struct user_namespace *user_ns)
 {
-	uid_t uid = from_kuid_munged(sk_user_ns(nlskb->sk), sock_i_uid(sk));
+	uid_t uid = from_kuid_munged(user_ns, sock_i_uid(sk));
 	return nla_put(nlskb, UNIX_DIAG_UID, sizeof(uid_t), &uid);
 }
 
 static int sk_diag_fill(struct sock *sk, struct sk_buff *skb, struct unix_diag_req *req,
-		u32 portid, u32 seq, u32 flags, int sk_ino)
+			struct user_namespace *user_ns,
+			u32 portid, u32 seq, u32 flags, int sk_ino)
 {
 	struct nlmsghdr *nlh;
 	struct unix_diag_msg *rep;
@@ -167,7 +169,7 @@ static int sk_diag_fill(struct sock *sk, struct sk_buff *skb, struct unix_diag_r
 		goto out_nlmsg_trim;
 
 	if ((req->udiag_show & UDIAG_SHOW_UID) &&
-	    sk_diag_dump_uid(sk, skb))
+	    sk_diag_dump_uid(sk, skb, user_ns))
 		goto out_nlmsg_trim;
 
 	nlmsg_end(skb, nlh);
@@ -179,7 +181,8 @@ static int sk_diag_fill(struct sock *sk, struct sk_buff *skb, struct unix_diag_r
 }
 
 static int sk_diag_dump(struct sock *sk, struct sk_buff *skb, struct unix_diag_req *req,
-		u32 portid, u32 seq, u32 flags)
+			struct user_namespace *user_ns,
+			u32 portid, u32 seq, u32 flags)
 {
 	int sk_ino;
 
@@ -190,7 +193,7 @@ static int sk_diag_dump(struct sock *sk, struct sk_buff *skb, struct unix_diag_r
 	if (!sk_ino)
 		return 0;
 
-	return sk_diag_fill(sk, skb, req, portid, seq, flags, sk_ino);
+	return sk_diag_fill(sk, skb, req, user_ns, portid, seq, flags, sk_ino);
 }
 
 static int unix_diag_dump(struct sk_buff *skb, struct netlink_callback *cb)
@@ -214,7 +217,7 @@ static int unix_diag_dump(struct sk_buff *skb, struct netlink_callback *cb)
 				goto next;
 			if (!(req->udiag_states & (1 << sk->sk_state)))
 				goto next;
-			if (sk_diag_dump(sk, skb, req,
+			if (sk_diag_dump(sk, skb, req, sk_user_ns(skb->sk),
 					 NETLINK_CB(cb->skb).portid,
 					 cb->nlh->nlmsg_seq,
 					 NLM_F_MULTI) < 0) {
@@ -282,7 +285,8 @@ static int unix_diag_get_exact(struct sk_buff *in_skb,
 	if (!rep)
 		goto out;
 
-	err = sk_diag_fill(sk, rep, req, NETLINK_CB(in_skb).portid,
+	err = sk_diag_fill(sk, rep, req, sk_user_ns(NETLINK_CB(in_skb).sk),
+			   NETLINK_CB(in_skb).portid,
 			   nlh->nlmsg_seq, 0, req->udiag_ino);
 	if (err < 0) {
 		nlmsg_free(rep);

tools/testing/selftests/net/.gitignore

 # SPDX-License-Identifier: GPL-2.0-only
 bind_bhash
 cmsg_sender
+diag_uid
 fin_ack_lat
 gro
 hwtstamp_config

tools/testing/selftests/net/af_unix/Makefile

-TEST_GEN_PROGS := test_unix_oob unix_connect
+TEST_GEN_PROGS := diag_uid test_unix_oob unix_connect
 
 include ../../lib.mk

tools/testing/selftests/net/af_unix/diag_uid.c

+// SPDX-License-Identifier: GPL-2.0
+/* Copyright Amazon.com Inc. or its affiliates. */
+
+#define _GNU_SOURCE
+#include <sched.h>
+
+#include <unistd.h>
+#include <linux/netlink.h>
+#include <linux/rtnetlink.h>
+#include <linux/sock_diag.h>
+#include <linux/unix_diag.h>
+#include <sys/socket.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <sys/un.h>
+
+#include "../../kselftest_harness.h"
+
+FIXTURE(diag_uid)
+{
+	int netlink_fd;
+	int unix_fd;
+	__u32 inode;
+	__u64 cookie;
+};
+
+FIXTURE_VARIANT(diag_uid)
+{
+	int unshare;
+	int udiag_show;
+};
+
+FIXTURE_VARIANT_ADD(diag_uid, uid)
+{
+	.unshare = 0,
+	.udiag_show = UDIAG_SHOW_UID
+};
+
+FIXTURE_VARIANT_ADD(diag_uid, uid_unshare)
+{
+	.unshare = CLONE_NEWUSER,
+	.udiag_show = UDIAG_SHOW_UID
+};
+
+FIXTURE_SETUP(diag_uid)
+{
+	struct stat file_stat;
+	socklen_t optlen;
+	int ret;
+
+	if (variant->unshare)
+		ASSERT_EQ(unshare(variant->unshare), 0);
+
+	self->netlink_fd = socket(AF_NETLINK, SOCK_RAW, NETLINK_SOCK_DIAG);
+	ASSERT_NE(self->netlink_fd, -1);
+
+	self->unix_fd = socket(AF_UNIX, SOCK_STREAM, 0);
+	ASSERT_NE(self->unix_fd, -1);
+
+	ret = fstat(self->unix_fd, &file_stat);
+	ASSERT_EQ(ret, 0);
+
+	self->inode = file_stat.st_ino;
+
+	optlen = sizeof(self->cookie);
+	ret = getsockopt(self->unix_fd, SOL_SOCKET, SO_COOKIE, &self->cookie, &optlen);
+	ASSERT_EQ(ret, 0);
+}
+
+FIXTURE_TEARDOWN(diag_uid)
+{
+	close(self->netlink_fd);
+	close(self->unix_fd);
+}
+
+int send_request(struct __test_metadata *_metadata,
+		 FIXTURE_DATA(diag_uid) *self,
+		 const FIXTURE_VARIANT(diag_uid) *variant)
+{
+	struct {
+		struct nlmsghdr nlh;
+		struct unix_diag_req udr;
+	} req = {
+		.nlh = {
+			.nlmsg_len = sizeof(req),
+			.nlmsg_type = SOCK_DIAG_BY_FAMILY,
+			.nlmsg_flags = NLM_F_REQUEST
+		},
+		.udr = {
+			.sdiag_family = AF_UNIX,
+			.udiag_ino = self->inode,
+			.udiag_cookie = {
+				(__u32)self->cookie,
+				(__u32)(self->cookie >> 32)
+			},
+			.udiag_show = variant->udiag_show
+		}
+	};
+	struct sockaddr_nl nladdr = {
+		.nl_family = AF_NETLINK
+	};
+	struct iovec iov = {
+		.iov_base = &req,
+		.iov_len = sizeof(req)
+	};
+	struct msghdr msg = {
+		.msg_name = &nladdr,
+		.msg_namelen = sizeof(nladdr),
+		.msg_iov = &iov,
+		.msg_iovlen = 1
+	};
+
+	return sendmsg(self->netlink_fd, &msg, 0);
+}
+
+void render_response(struct __test_metadata *_metadata,
+		     struct unix_diag_req *udr, __u32 len)
+{
+	unsigned int rta_len = len - NLMSG_LENGTH(sizeof(*udr));
+	struct rtattr *attr;
+	uid_t uid;
+
+	ASSERT_GT(len, sizeof(*udr));
+	ASSERT_EQ(udr->sdiag_family, AF_UNIX);
+
+	attr = (struct rtattr *)(udr + 1);
+	ASSERT_NE(RTA_OK(attr, rta_len), 0);
+	ASSERT_EQ(attr->rta_type, UNIX_DIAG_UID);
+
+	uid = *(uid_t *)RTA_DATA(attr);
+	ASSERT_EQ(uid, getuid());
+}
+
+void receive_response(struct __test_metadata *_metadata,
+		      FIXTURE_DATA(diag_uid) *self)
+{
+	long buf[8192 / sizeof(long)];
+	struct sockaddr_nl nladdr = {
+		.nl_family = AF_NETLINK
+	};
+	struct iovec iov = {
+		.iov_base = buf,
+		.iov_len = sizeof(buf)
+	};
+	struct msghdr msg = {
+		.msg_name = &nladdr,
+		.msg_namelen = sizeof(nladdr),
+		.msg_iov = &iov,
+		.msg_iovlen = 1
+	};
+	struct unix_diag_req *udr;
+	struct nlmsghdr *nlh;
+	int ret;
+
+	ret = recvmsg(self->netlink_fd, &msg, 0);
+	ASSERT_GT(ret, 0);
+
+	nlh = (struct nlmsghdr *)buf;
+	ASSERT_NE(NLMSG_OK(nlh, ret), 0);
+	ASSERT_EQ(nlh->nlmsg_type, SOCK_DIAG_BY_FAMILY);
+
+	render_response(_metadata, NLMSG_DATA(nlh), nlh->nlmsg_len);
+
+	nlh = NLMSG_NEXT(nlh, ret);
+	ASSERT_EQ(NLMSG_OK(nlh, ret), 0);
+}
+
+TEST_F(diag_uid, 1)
+{
+	int ret;
+
+	ret = send_request(_metadata, self, variant);
+	ASSERT_GT(ret, 0);
+
+	receive_response(_metadata, self);
+}
+
+TEST_HARNESS_MAIN