niu: Fix kernel buffer overflow for ETHTOOL_GRXCLSRLALL

niu_get_ethtool_tcam_all() assumes that its output buffer is the right
size, and warns before returning if it is not.  However, the output
buffer size is under user control and ETHTOOL_GRXCLSRLALL is an
unprivileged ethtool command.  Therefore this is at least a local
denial-of-service vulnerability.

Change it to check before writing each entry and to return an error if
the buffer is already full.

Compile-tested only.

Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/niu.c b/drivers/net/niu.c
index b9b950845b0e7d480a020f997f6707b89258f13e..340cbec4894321fc8e6257f19dfb5242701e659e 100644 (file)
--- a/drivers/net/niu.c
+++ b/drivers/net/niu.c
@@ -7272,32 +7272,28 @@ static int niu_get_ethtool_tcam_all(struct niu *np,
        struct niu_parent *parent = np->parent;
        struct niu_tcam_entry *tp;
        int i, idx, cnt;
-       u16 n_entries;
        unsigned long flags;
-
+       int ret = 0;
 
        /* put the tcam size here */
        nfc->data = tcam_get_size(np);
 
        niu_lock_parent(np, flags);
-       n_entries = nfc->rule_cnt;
        for (cnt = 0, i = 0; i < nfc->data; i++) {
                idx = tcam_get_index(np, i);
                tp = &parent->tcam[idx];
                if (!tp->valid)
                        continue;
+               if (cnt == nfc->rule_cnt) {
+                       ret = -EMSGSIZE;
+                       break;
+               }
                rule_locs[cnt] = i;
                cnt++;
        }
        niu_unlock_parent(np, flags);
 
-       if (n_entries != cnt) {
-               /* print warning, this should not happen */
-               netdev_info(np->dev, "niu%d: In %s(): n_entries[%d] != cnt[%d]!!!\n",
-                           np->parent->index, __func__, n_entries, cnt);
-       }
-
-       return 0;
+       return ret;
 }
 
 static int niu_get_nfc(struct net_device *dev, struct ethtool_rxnfc *cmd,