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>

diff --git a/net/ipv4/proc.c b/net/ipv4/proc.c
index 8f5a403f6f6b9487b62eec845664d960c056bc8c..a631a1f110caab546d4d5e46aff34d7f67c66f03 100644 (file)
--- 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
 }