net: fix /proc/net/snmp as memory corruptor

icmpmsg_put() can happily corrupt kernel memory, using a static
table and forgetting to reset an array index in a loop.

Remove the static array since its not safe without proper locking.

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 30 insertions, 28 deletions

diff --git a/net/ipv4/proc.c b/net/ipv4/proc.c
index 8f5a403f6f6b..a631a1f110ca 100644
--- a/net/ipv4/proc.c
+++ b/net/ipv4/proc.c
@@ -237,43 +237,45 @@ static const struct snmp_mib snmp4_net_list[] = {
         SNMP_MIB_SENTINEL
 };
 
+static void icmpmsg_put_line(struct seq_file *seq, unsigned long *vals,
+                             unsigned short *type, int count)
+{
+        int j;
+
+        if (count) {
+                seq_printf(seq, "\nIcmpMsg:");
+                for (j = 0; j < count; ++j)
+                        seq_printf(seq, " %sType%u",
+                                type[j] & 0x100 ? "Out" : "In",
+                                type[j] & 0xff);
+                seq_printf(seq, "\nIcmpMsg:");
+                for (j = 0; j < count; ++j)
+                        seq_printf(seq, " %lu", vals[j]);
+        }
+}
+
 static void icmpmsg_put(struct seq_file *seq)
 {
 #define PERLINE 16
 
-        int j, i, count;
-        static int out[PERLINE];
+        int i, count;
+        unsigned short type[PERLINE];
+        unsigned long vals[PERLINE], val;
         struct net *net = seq->private;
 
         count = 0;
         for (i = 0; i < ICMPMSG_MIB_MAX; i++) {
-
-                if (snmp_fold_field((void **) net->mib.icmpmsg_statistics, i))
-                        out[count++] = i;
-                if (count < PERLINE)
-                        continue;
-
-                seq_printf(seq, "\nIcmpMsg:");
-                for (j = 0; j < PERLINE; ++j)
-                        seq_printf(seq, " %sType%u", i & 0x100 ? "Out" : "In",
-                                        i & 0xff);
-                seq_printf(seq, "\nIcmpMsg: ");
-                for (j = 0; j < PERLINE; ++j)
-                        seq_printf(seq, " %lu",
-                                snmp_fold_field((void **) net->mib.icmpmsg_statistics,
-                                out[j]));
-                seq_putc(seq, '\n');
-        }
-        if (count) {
-                seq_printf(seq, "\nIcmpMsg:");
-                for (j = 0; j < count; ++j)
-                        seq_printf(seq, " %sType%u", out[j] & 0x100 ? "Out" :
-                                "In", out[j] & 0xff);
-                seq_printf(seq, "\nIcmpMsg:");
-                for (j = 0; j < count; ++j)
-                        seq_printf(seq, " %lu", snmp_fold_field((void **)
-                                net->mib.icmpmsg_statistics, out[j]));
+                val = snmp_fold_field((void **) net->mib.icmpmsg_statistics, i);
+                if (val) {
+                        type[count] = i;
+                        vals[count++] = val;
+                }
+                if (count == PERLINE) {
+                        icmpmsg_put_line(seq, vals, type, count);
+                        count = 0;
+                }
         }
+        icmpmsg_put_line(seq, vals, type, count);
 
 #undef PERLINE
 }