diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 9bcdec3..366834b 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -3276,9 +3276,23 @@ void __init tcp_init(void)
 	sysctl_tcp_max_orphans = cnt / 2;
 	sysctl_max_syn_backlog = max(128, cnt / 256);
 
+	/*
+	 * Despite the sysctl name, those values are always used in the code.
+	 * CONFIG_PROC_SYSCTL only exposes it as a sysctl, allowing the admin
+	 * to tweak them. If this is not configured, we need to provide
+	 * a default value here
+	 */
+#ifdef CONFIG_PROC_SYSCTL
 	/* Set per-socket limits to no more than 1/128 the pressure threshold */
 	limit = ((unsigned long)init_net.ipv4.sysctl_tcp_mem[1])
 		<< (PAGE_SHIFT - 7);
+#else
+	limit = nr_free_buffer_pages() / 8;
+	limit = max(limit, 128UL);
+	init_net.ipv4.sysctl_tcp_mem[0] = limit / 4 * 3;
+	init_net.ipv4.sysctl_tcp_mem[1] = limit;
+	init_net.ipv4.sysctl_tcp_mem[2] = sysctl_tcp_mem[0] * 2;
+#endif
 	max_share = min(4UL*1024*1024, limit);
 
 	sysctl_tcp_wmem[0] = SK_MEM_QUANTUM;