[PKT_SCHED]: Fix illegal memory dereferences when dumping actions

The TCA_ACT_KIND attribute is used without checking its
availability when dumping actions therefore leading to a
value of 0x4 being dereferenced.

The use of strcmp() in tc_lookup_action_n() isn't safe
when fed with string from an attribute without enforcing
proper NUL termination.

Both bugs can be triggered with malformed netlink message
and don't require any privileges.

Signed-off-by: Thomas Graf <tgraf@suug.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 5 insertions, 6 deletions

diff --git a/net/sched/act_api.c b/net/sched/act_api.c
index 5b9397b33238..f9d1d78e17f8 100644
--- a/net/sched/act_api.c
+++ b/net/sched/act_api.c
@@ -776,7 +776,7 @@ replay:
         return ret;
 }
 
-static char *
+static struct rtattr *
 find_dump_kind(struct nlmsghdr *n)
 {
         struct rtattr *tb1, *tb2[TCA_ACT_MAX+1];
@@ -804,7 +804,7 @@ find_dump_kind(struct nlmsghdr *n)
                 return NULL;
         kind = tb2[TCA_ACT_KIND-1];
 
-        return (char *) RTA_DATA(kind);
+        return kind;
 }
 
 static int
@@ -817,16 +817,15 @@ tc_dump_action(struct sk_buff *skb, struct netlink_callback *cb)
         struct tc_action a;
         int ret = 0;
         struct tcamsg *t = (struct tcamsg *) NLMSG_DATA(cb->nlh);
-        char *kind = find_dump_kind(cb->nlh);
+        struct rtattr *kind = find_dump_kind(cb->nlh);
 
         if (kind == NULL) {
                 printk("tc_dump_action: action bad kind\n");
                 return 0;
         }
 
-        a_o = tc_lookup_action_n(kind);
+        a_o = tc_lookup_action(kind);
         if (a_o == NULL) {
-                printk("failed to find %s\n", kind);
                 return 0;
         }
 
@@ -834,7 +833,7 @@ tc_dump_action(struct sk_buff *skb, struct netlink_callback *cb)
         a.ops = a_o;
 
         if (a_o->walk == NULL) {
-                printk("tc_dump_action: %s !capable of dumping table\n", kind);
+                printk("tc_dump_action: %s !capable of dumping table\n", a_o->kind);
                 goto rtattr_failure;
         }