net/rds: Whitelist rdma_cookie and rx_tstamp for usercopy

Add the RDMA cookie and RX timestamp to the usercopy whitelist.

After the introduction of hardened usercopy whitelisting
(https://lwn.net/Articles/727322/), a warning is displayed when the
RDMA cookie or RX timestamp is copied to userspace:

kernel: WARNING: CPU: 3 PID: 5750 at
mm/usercopy.c:81 usercopy_warn+0x8e/0xa6
[...]
kernel: Call Trace:
kernel: __check_heap_object+0xb8/0x11b
kernel: __check_object_size+0xe3/0x1bc
kernel: put_cmsg+0x95/0x115
kernel: rds_recvmsg+0x43d/0x620 [rds]
kernel: sock_recvmsg+0x43/0x4a
kernel: ___sys_recvmsg+0xda/0x1e6
kernel: ? __handle_mm_fault+0xcae/0xf79
kernel: __sys_recvmsg+0x51/0x8a
kernel: SyS_recvmsg+0x12/0x1c
kernel: do_syscall_64+0x79/0x1ae

When the whitelisting feature was introduced, the memory for the RDMA
cookie and RX timestamp in RDS was not added to the whitelist, causing
the warning above.

Signed-off-by: Dag Moxnes <[e-mail]>
Tested-by: Jenny <[e-mail]>
Acked-by: Santosh Shilimkar <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

net/rds/ib_recv.c

···
 	si_meminfo(&si);
 	rds_ib_sysctl_max_recv_allocation = si.totalram / 3 * PAGE_SIZE / RDS_FRAG_SIZE;
 
-	rds_ib_incoming_slab = kmem_cache_create("rds_ib_incoming",
-					sizeof(struct rds_ib_incoming),
-					0, SLAB_HWCACHE_ALIGN, NULL);
+	rds_ib_incoming_slab =
+		kmem_cache_create_usercopy("rds_ib_incoming",
+					   sizeof(struct rds_ib_incoming),
+					   0, SLAB_HWCACHE_ALIGN,
+					   offsetof(struct rds_ib_incoming,
+						    ii_inc.i_usercopy),
+					   sizeof(struct rds_inc_usercopy),
+					   NULL);
 	if (!rds_ib_incoming_slab)
 		goto out;
 

net/rds/rds.h

···
 #define	RDS_MSG_RX_END		2
 #define	RDS_MSG_RX_CMSG		3
 
+/* The following values are whitelisted for usercopy */
+struct rds_inc_usercopy {
+	rds_rdma_cookie_t	rdma_cookie;
+	ktime_t			rx_tstamp;
+};
+
 struct rds_incoming {
 	refcount_t		i_refcount;
 	struct list_head	i_item;
···
 	unsigned long		i_rx_jiffies;
 	struct in6_addr		i_saddr;
 
-	rds_rdma_cookie_t	i_rdma_cookie;
-	ktime_t			i_rx_tstamp;
+	struct rds_inc_usercopy i_usercopy;
 	u64			i_rx_lat_trace[RDS_RX_MAX_TRACES];
 };
 

net/rds/recv.c

···
 	INIT_LIST_HEAD(&inc->i_item);
 	inc->i_conn = conn;
 	inc->i_saddr = *saddr;
-	inc->i_rdma_cookie = 0;
-	inc->i_rx_tstamp = ktime_set(0, 0);
+	inc->i_usercopy.rdma_cookie = 0;
+	inc->i_usercopy.rx_tstamp = ktime_set(0, 0);
 
 	memset(inc->i_rx_lat_trace, 0, sizeof(inc->i_rx_lat_trace));
 }
···
 	inc->i_conn = cp->cp_conn;
 	inc->i_conn_path = cp;
 	inc->i_saddr = *saddr;
-	inc->i_rdma_cookie = 0;
-	inc->i_rx_tstamp = ktime_set(0, 0);
+	inc->i_usercopy.rdma_cookie = 0;
+	inc->i_usercopy.rx_tstamp = ktime_set(0, 0);
 }
 EXPORT_SYMBOL_GPL(rds_inc_path_init);
 
···
 		case RDS_EXTHDR_RDMA_DEST:
 			/* We ignore the size for now. We could stash it
 			 * somewhere and use it for error checking. */
-			inc->i_rdma_cookie = rds_rdma_make_cookie(
+			inc->i_usercopy.rdma_cookie = rds_rdma_make_cookie(
 					be32_to_cpu(buffer.rdma_dest.h_rdma_rkey),
 					be32_to_cpu(buffer.rdma_dest.h_rdma_offset));
 
···
 				      be32_to_cpu(inc->i_hdr.h_len),
 				      inc->i_hdr.h_dport);
 		if (sock_flag(sk, SOCK_RCVTSTAMP))
-			inc->i_rx_tstamp = ktime_get_real();
+			inc->i_usercopy.rx_tstamp = ktime_get_real();
 		rds_inc_addref(inc);
 		inc->i_rx_lat_trace[RDS_MSG_RX_END] = local_clock();
 		list_add_tail(&inc->i_item, &rs->rs_recv_queue);
···
 {
 	int ret = 0;
 
-	if (inc->i_rdma_cookie) {
+	if (inc->i_usercopy.rdma_cookie) {
 		ret = put_cmsg(msg, SOL_RDS, RDS_CMSG_RDMA_DEST,
-				sizeof(inc->i_rdma_cookie), &inc->i_rdma_cookie);
+				sizeof(inc->i_usercopy.rdma_cookie),
+				&inc->i_usercopy.rdma_cookie);
 		if (ret)
 			goto out;
 	}
 
-	if ((inc->i_rx_tstamp != 0) &&
+	if ((inc->i_usercopy.rx_tstamp != 0) &&
 	    sock_flag(rds_rs_to_sk(rs), SOCK_RCVTSTAMP)) {
-		struct __kernel_old_timeval tv = ns_to_kernel_old_timeval(inc->i_rx_tstamp);
+		struct __kernel_old_timeval tv =
+			ns_to_kernel_old_timeval(inc->i_usercopy.rx_tstamp);
 
 		if (!sock_flag(rds_rs_to_sk(rs), SOCK_TSTAMP_NEW)) {
 			ret = put_cmsg(msg, SOL_SOCKET, SO_TIMESTAMP_OLD,