act_pedit: access skb->data safely

access skb->data safely

we should use skb_header_pointer() and skb_store_bits() to access skb->data to
handle small or non-linear skbs.

Signed-off-by: Changli Gao <xiaosuo@gmail.com>
----
 net/sched/act_pedit.c |   24 ++++++++++++++----------
 1 file changed, 14 insertions(+), 10 deletions(-)
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 14 insertions, 10 deletions

diff --git a/net/sched/act_pedit.c b/net/sched/act_pedit.c
index fdbd0b7bd840..50e3d945e1f4 100644
--- a/net/sched/act_pedit.c
+++ b/net/sched/act_pedit.c
@@ -125,7 +125,7 @@ static int tcf_pedit(struct sk_buff *skb, struct tc_action *a,
 {
         struct tcf_pedit *p = a->priv;
         int i, munged = 0;
-        u8 *pptr;
+        unsigned int off;
 
         if (!(skb->tc_verd & TC_OK2MUNGE)) {
                 /* should we set skb->cloned? */
@@ -134,7 +134,7 @@ static int tcf_pedit(struct sk_buff *skb, struct tc_action *a,
                 }
         }
 
-        pptr = skb_network_header(skb);
+        off = skb_network_offset(skb);
 
         spin_lock(&p->tcf_lock);
 
@@ -144,17 +144,17 @@ static int tcf_pedit(struct sk_buff *skb, struct tc_action *a,
                 struct tc_pedit_key *tkey = p->tcfp_keys;
 
                 for (i = p->tcfp_nkeys; i > 0; i--, tkey++) {
-                        u32 *ptr;
+                        u32 *ptr, _data;
                         int offset = tkey->off;
 
                         if (tkey->offmask) {
-                                if (skb->len > tkey->at) {
-                                         char *j = pptr + tkey->at;
-                                         offset += ((*j & tkey->offmask) >>
-                                                   tkey->shift);
-                                } else {
+                                char *d, _d;
+
+                                d = skb_header_pointer(skb, off + tkey->at, 1,
+                                                       &_d);
+                                if (!d)
                                         goto bad;
-                                }
+                                offset += (*d & tkey->offmask) >> tkey->shift;
                         }
 
                         if (offset % 4) {
@@ -169,9 +169,13 @@ static int tcf_pedit(struct sk_buff *skb, struct tc_action *a,
                                 goto bad;
                         }
 
-                        ptr = (u32 *)(pptr+offset);
+                        ptr = skb_header_pointer(skb, off + offset, 4, &_data);
+                        if (!ptr)
+                                goto bad;
                         /* just do it, baby */
                         *ptr = ((*ptr & tkey->mask) ^ tkey->val);
+                        if (ptr == &_data)
+                                skb_store_bits(skb, off + offset, ptr, 4);
                         munged++;
                 }