1 files changed, 26 insertions, 4 deletions

diff --git a/net/sched/act_pedit.c b/net/sched/act_pedit.c
index ff4f2437b592..f095a0fb75c6 100644
--- a/net/sched/act_pedit.c
+++ b/net/sched/act_pedit.c
@@ -148,7 +148,7 @@ static int tcf_pedit_init(struct net *net, struct nlattr *nla,
 	struct nlattr *pattr;
 	struct tcf_pedit *p;
 	int ret = 0, err;
-	int ksize;
+	int i, ksize;
 	u32 index;
 
 	if (!nla) {
@@ -227,6 +227,22 @@ static int tcf_pedit_init(struct net *net, struct nlattr *nla,
 		p->tcfp_nkeys = parm->nkeys;
 	}
 	memcpy(p->tcfp_keys, parm->keys, ksize);
+	p->tcfp_off_max_hint = 0;
+	for (i = 0; i < p->tcfp_nkeys; ++i) {
+		u32 cur = p->tcfp_keys[i].off;
+
+		/* sanitize the shift value for any later use */
+		p->tcfp_keys[i].shift = min_t(size_t, BITS_PER_TYPE(int) - 1,
+					      p->tcfp_keys[i].shift);
+
+		/* The AT option can read a single byte, we can bound the actual
+		 * value with uchar max.
+		 */
+		cur += (0xff & p->tcfp_keys[i].offmask) >> p->tcfp_keys[i].shift;
+
+		/* Each key touches 4 bytes starting from the computed offset */
+		p->tcfp_off_max_hint = max(p->tcfp_off_max_hint, cur + 4);
+	}
 
 	p->tcfp_flags = parm->flags;
 	goto_ch = tcf_action_set_ctrlact(*a, parm->action, goto_ch);
@@ -307,13 +323,18 @@ static int tcf_pedit_act(struct sk_buff *skb, const struct tc_action *a,
 			 struct tcf_result *res)
 {
 	struct tcf_pedit *p = to_pedit(a);
+	u32 max_offset;
 	int i;
 
-	if (skb_unclone(skb, GFP_ATOMIC))
-		return p->tcf_action;
-
 	spin_lock(&p->tcf_lock);
 
+	max_offset = (skb_transport_header_was_set(skb) ?
+		      skb_transport_offset(skb) :
+		      skb_network_offset(skb)) +
+		     p->tcfp_off_max_hint;
+	if (skb_ensure_writable(skb, min(skb->len, max_offset)))
+		goto unlock;
+
 	tcf_lastuse_update(&p->tcf_tm);
 
 	if (p->tcfp_nkeys > 0) {
@@ -402,6 +423,7 @@ bad:
 	p->tcf_qstats.overlimits++;
 done:
 	bstats_update(&p->tcf_bstats, skb);
+unlock:
 	spin_unlock(&p->tcf_lock);
 	return p->tcf_action;
 }