hisax: Fix unchecked alloc_skb() return.

Jesper Juhl noticed that l2_pull_iqueue() does not
check to see if alloc_skb() fails.

Fix this by first trying to reallocate the headroom
if necessary, rather than later after we've made hard
to undo state changes.

Reported-by: Jesper Juhl <jj@chaosbits.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 20 insertions, 15 deletions

diff --git a/drivers/isdn/hisax/isdnl2.c b/drivers/isdn/hisax/isdnl2.c
index 0858791978d8..98ac835281fe 100644
--- a/drivers/isdn/hisax/isdnl2.c
+++ b/drivers/isdn/hisax/isdnl2.c
@@ -1243,14 +1243,21 @@ l2_st7_tout_203(struct FsmInst *fi, int event, void *arg)
         st->l2.rc = 0;
 }
 
+static int l2_hdr_space_needed(struct Layer2 *l2)
+{
+        int len = test_bit(FLG_LAPD, &l2->flag) ? 2 : 1;
+
+        return len + (test_bit(FLG_LAPD, &l2->flag) ? 2 : 1);
+}
+
 static void
 l2_pull_iqueue(struct FsmInst *fi, int event, void *arg)
 {
         struct PStack *st = fi->userdata;
-        struct sk_buff *skb, *oskb;
+        struct sk_buff *skb;
         struct Layer2 *l2 = &st->l2;
         u_char header[MAX_HEADER_LEN];
-        int i;
+        int i, hdr_space_needed;
         int unsigned p1;
         u_long flags;
 
@@ -1261,6 +1268,16 @@ l2_pull_iqueue(struct FsmInst *fi, int event, void *arg)
         if (!skb)
                 return;
 
+        hdr_space_needed = l2_hdr_space_needed(l2);
+        if (hdr_space_needed > skb_headroom(skb)) {
+                struct sk_buff *orig_skb = skb;
+
+                skb = skb_realloc_headroom(skb, hdr_space_needed);
+                if (!skb) {
+                        dev_kfree_skb(orig_skb);
+                        return;
+                }
+        }
         spin_lock_irqsave(&l2->lock, flags);
         if(test_bit(FLG_MOD128, &l2->flag))
                 p1 = (l2->vs - l2->va) % 128;
@@ -1285,19 +1302,7 @@ l2_pull_iqueue(struct FsmInst *fi, int event, void *arg)
                 l2->vs = (l2->vs + 1) % 8;
         }
         spin_unlock_irqrestore(&l2->lock, flags);
-        p1 = skb->data - skb->head;
-        if (p1 >= i)
-                memcpy(skb_push(skb, i), header, i);
-        else {
-                printk(KERN_WARNING
-                "isdl2 pull_iqueue skb header(%d/%d) too short\n", i, p1);
-                oskb = skb;
-                skb = alloc_skb(oskb->len + i, GFP_ATOMIC);
-                memcpy(skb_put(skb, i), header, i);
-                skb_copy_from_linear_data(oskb,
-                                          skb_put(skb, oskb->len), oskb->len);
-                dev_kfree_skb(oskb);
-        }
+        memcpy(skb_push(skb, i), header, i);
         st->l2.l2l1(st, PH_PULL | INDICATION, skb);
         test_and_clear_bit(FLG_ACK_PEND, &st->l2.flag);
         if (!test_and_set_bit(FLG_T200_RUN, &st->l2.flag)) {