neigh: prevent overflowing params in /proc/sys/net/ipv4/neigh/

Without this patch, the fields app_solicit, gc_thresh1, gc_thresh2,
gc_thresh3, proxy_qlen, ucast_solicit, mcast_solicit could have
assumed negative values when setting large numbers.
Signed-off-by: Francesco Fusco <ffusco@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/core/neighbour.c

@@ -2767,6 +2767,7 @@ EXPORT_SYMBOL(neigh_app_ns);
 
 #ifdef CONFIG_SYSCTL
 static int zero;
+static int int_max = INT_MAX;
 static int unres_qlen_max = INT_MAX / SKB_TRUESIZE(ETH_FRAME_LEN);
 
 static int proc_unres_qlen(struct ctl_table *ctl, int write,
@@ -2819,19 +2820,25 @@ static struct neigh_sysctl_table {
 			.procname	= "mcast_solicit",
 			.maxlen		= sizeof(int),
 			.mode		= 0644,
-			.proc_handler	= proc_dointvec,
+			.extra1 	= &zero,
+			.extra2		= &int_max,
+			.proc_handler	= proc_dointvec_minmax,
 		},
 		[NEIGH_VAR_UCAST_PROBE] = {
 			.procname	= "ucast_solicit",
 			.maxlen		= sizeof(int),
 			.mode		= 0644,
-			.proc_handler	= proc_dointvec,
+			.extra1 	= &zero,
+			.extra2		= &int_max,
+			.proc_handler	= proc_dointvec_minmax,
 		},
 		[NEIGH_VAR_APP_PROBE] = {
 			.procname	= "app_solicit",
 			.maxlen		= sizeof(int),
 			.mode		= 0644,
-			.proc_handler	= proc_dointvec,
+			.extra1 	= &zero,
+			.extra2		= &int_max,
+			.proc_handler	= proc_dointvec_minmax,
 		},
 		[NEIGH_VAR_RETRANS_TIME] = {
 			.procname	= "retrans_time",
@@ -2874,7 +2881,9 @@ static struct neigh_sysctl_table {
 			.procname	= "proxy_qlen",
 			.maxlen		= sizeof(int),
 			.mode		= 0644,
-			.proc_handler	= proc_dointvec,
+			.extra1 	= &zero,
+			.extra2		= &int_max,
+			.proc_handler	= proc_dointvec_minmax,
 		},
 		[NEIGH_VAR_ANYCAST_DELAY] = {
 			.procname	= "anycast_delay",
@@ -2916,19 +2925,25 @@ static struct neigh_sysctl_table {
 			.procname	= "gc_thresh1",
 			.maxlen		= sizeof(int),
 			.mode		= 0644,
-			.proc_handler	= proc_dointvec,
+			.extra1 	= &zero,
+			.extra2		= &int_max,
+			.proc_handler	= proc_dointvec_minmax,
 		},
 		[NEIGH_VAR_GC_THRESH2] = {
 			.procname	= "gc_thresh2",
 			.maxlen		= sizeof(int),
 			.mode		= 0644,
-			.proc_handler	= proc_dointvec,
+			.extra1 	= &zero,
+			.extra2		= &int_max,
+			.proc_handler	= proc_dointvec_minmax,
 		},
 		[NEIGH_VAR_GC_THRESH3] = {
 			.procname	= "gc_thresh3",
 			.maxlen		= sizeof(int),
 			.mode		= 0644,
-			.proc_handler	= proc_dointvec,
+			.extra1 	= &zero,
+			.extra2		= &int_max,
+			.proc_handler	= proc_dointvec_minmax,
 		},
 		{},
 	},