net: sched: ife: handle malformed tlv length

There is currently no handling to check on a invalid tlv length. This
patch adds such handling to avoid killing the kernel with a malformed
ife packet.

Signed-off-by: Alexander Aring <aring@mojatatu.com>
Reviewed-by: Yotam Gigi <yotam.gi@gmail.com>
Acked-by: Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

3 files changed, 41 insertions, 4 deletions

diff --git a/include/net/ife.h b/include/net/ife.h
index 44b9c00f7223..e117617e3c34 100644
--- a/include/net/ife.h
+++ b/include/net/ife.h
@@ -12,7 +12,8 @@
 void *ife_encode(struct sk_buff *skb, u16 metalen);
 void *ife_decode(struct sk_buff *skb, u16 *metalen);
 
-void *ife_tlv_meta_decode(void *skbdata, u16 *attrtype, u16 *dlen, u16 *totlen);
+void *ife_tlv_meta_decode(void *skbdata, const void *ifehdr_end, u16 *attrtype,
+                          u16 *dlen, u16 *totlen);
 int ife_tlv_meta_encode(void *skbdata, u16 attrtype, u16 dlen,
                         const void *dval);
 
diff --git a/net/ife/ife.c b/net/ife/ife.c
index 7d1ec76e7f43..7fbe70a0af4b 100644
--- a/net/ife/ife.c
+++ b/net/ife/ife.c
@@ -92,12 +92,43 @@ struct meta_tlvhdr {
         __be16 len;
 };
 
+static bool __ife_tlv_meta_valid(const unsigned char *skbdata,
+                                 const unsigned char *ifehdr_end)
+{
+        const struct meta_tlvhdr *tlv;
+        u16 tlvlen;
+
+        if (unlikely(skbdata + sizeof(*tlv) > ifehdr_end))
+                return false;
+
+        tlv = (const struct meta_tlvhdr *)skbdata;
+        tlvlen = ntohs(tlv->len);
+
+        /* tlv length field is inc header, check on minimum */
+        if (tlvlen < NLA_HDRLEN)
+                return false;
+
+        /* overflow by NLA_ALIGN check */
+        if (NLA_ALIGN(tlvlen) < tlvlen)
+                return false;
+
+        if (unlikely(skbdata + NLA_ALIGN(tlvlen) > ifehdr_end))
+                return false;
+
+        return true;
+}
+
 /* Caller takes care of presenting data in network order
  */
-void *ife_tlv_meta_decode(void *skbdata, u16 *attrtype, u16 *dlen, u16 *totlen)
+void *ife_tlv_meta_decode(void *skbdata, const void *ifehdr_end, u16 *attrtype,
+                          u16 *dlen, u16 *totlen)
 {
-        struct meta_tlvhdr *tlv = (struct meta_tlvhdr *) skbdata;
+        struct meta_tlvhdr *tlv;
+
+        if (!__ife_tlv_meta_valid(skbdata, ifehdr_end))
+                return NULL;
 
+        tlv = (struct meta_tlvhdr *)skbdata;
         *dlen = ntohs(tlv->len) - NLA_HDRLEN;
         *attrtype = ntohs(tlv->type);
 
diff --git a/net/sched/act_ife.c b/net/sched/act_ife.c
index 49b8ab551fbe..8527cfdc446d 100644
--- a/net/sched/act_ife.c
+++ b/net/sched/act_ife.c
@@ -682,7 +682,12 @@ static int tcf_ife_decode(struct sk_buff *skb, const struct tc_action *a,
                 u16 mtype;
                 u16 dlen;
 
-                curr_data = ife_tlv_meta_decode(tlv_data, &mtype, &dlen, NULL);
+                curr_data = ife_tlv_meta_decode(tlv_data, ifehdr_end, &mtype,
+                                                &dlen, NULL);
+                if (!curr_data) {
+                        qstats_drop_inc(this_cpu_ptr(ife->common.cpu_qstats));
+                        return TC_ACT_SHOT;
+                }
 
                 if (find_decode_metaid(skb, ife, mtype, dlen, curr_data)) {
                         /* abuse overlimits to count when we receive metadata