Merge branch 'isdn-null-deref'

Karsten Keil says:

====================
Fix potential NULL pointer access and memory leak in ISDN layer2 functions

Insu Yun did brinup the issue with not checking the skb_clone() return
value in the layer2 I-frame ull functions.
This series fix the issue in a way which avoid protocol violations/data loss
on a temporary memory shortage.
====================
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/isdn/hisax/isdnl2.c

@@ -1247,7 +1247,7 @@ static void
 l2_pull_iqueue(struct FsmInst *fi, int event, void *arg)
 {
 	struct PStack *st = fi->userdata;
-	struct sk_buff *skb;
+	struct sk_buff *skb, *nskb;
 	struct Layer2 *l2 = &st->l2;
 	u_char header[MAX_HEADER_LEN];
 	int i, hdr_space_needed;
@@ -1262,14 +1262,10 @@ l2_pull_iqueue(struct FsmInst *fi, int event, void *arg)
 		return;
 
 	hdr_space_needed = l2headersize(l2, 0);
-	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;
-		}
+	nskb = skb_realloc_headroom(skb, hdr_space_needed);
+	if (!nskb) {
+		skb_queue_head(&l2->i_queue, skb);
+		return;
 	}
 	spin_lock_irqsave(&l2->lock, flags);
 	if (test_bit(FLG_MOD128, &l2->flag))
@@ -1282,7 +1278,7 @@ l2_pull_iqueue(struct FsmInst *fi, int event, void *arg)
 		       p1);
 		dev_kfree_skb(l2->windowar[p1]);
 	}
-	l2->windowar[p1] = skb_clone(skb, GFP_ATOMIC);
+	l2->windowar[p1] = skb;
 
 	i = sethdraddr(&st->l2, header, CMD);
 
@@ -1295,8 +1291,8 @@ l2_pull_iqueue(struct FsmInst *fi, int event, void *arg)
 		l2->vs = (l2->vs + 1) % 8;
 	}
 	spin_unlock_irqrestore(&l2->lock, flags);
-	memcpy(skb_push(skb, i), header, i);
-	st->l2.l2l1(st, PH_PULL | INDICATION, skb);
+	memcpy(skb_push(nskb, i), header, i);
+	st->l2.l2l1(st, PH_PULL | INDICATION, nskb);
 	test_and_clear_bit(FLG_ACK_PEND, &st->l2.flag);
 	if (!test_and_set_bit(FLG_T200_RUN, &st->l2.flag)) {
 		FsmDelTimer(&st->l2.t203, 13);

drivers/isdn/mISDN/layer2.c

@@ -1476,7 +1476,7 @@ static void
 l2_pull_iqueue(struct FsmInst *fi, int event, void *arg)
 {
 	struct layer2	*l2 = fi->userdata;
-	struct sk_buff	*skb, *nskb, *oskb;
+	struct sk_buff	*skb, *nskb;
 	u_char		header[MAX_L2HEADER_LEN];
 	u_int		i, p1;
 
@@ -1486,48 +1486,34 @@ l2_pull_iqueue(struct FsmInst *fi, int event, void *arg)
 	skb = skb_dequeue(&l2->i_queue);
 	if (!skb)
 		return;
-
-	if (test_bit(FLG_MOD128, &l2->flag))
-		p1 = (l2->vs - l2->va) % 128;
-	else
-		p1 = (l2->vs - l2->va) % 8;
-	p1 = (p1 + l2->sow) % l2->window;
-	if (l2->windowar[p1]) {
-		printk(KERN_WARNING "%s: l2 try overwrite ack queue entry %d\n",
-		       mISDNDevName4ch(&l2->ch), p1);
-		dev_kfree_skb(l2->windowar[p1]);
-	}
-	l2->windowar[p1] = skb;
 	i = sethdraddr(l2, header, CMD);
 	if (test_bit(FLG_MOD128, &l2->flag)) {
 		header[i++] = l2->vs << 1;
 		header[i++] = l2->vr << 1;
+	} else
+		header[i++] = (l2->vr << 5) | (l2->vs << 1);
+	nskb = skb_realloc_headroom(skb, i);
+	if (!nskb) {
+		printk(KERN_WARNING "%s: no headroom(%d) copy for IFrame\n",
+		       mISDNDevName4ch(&l2->ch), i);
+		skb_queue_head(&l2->i_queue, skb);
+		return;
+	}
+	if (test_bit(FLG_MOD128, &l2->flag)) {
+		p1 = (l2->vs - l2->va) % 128;
 		l2->vs = (l2->vs + 1) % 128;
 	} else {
-		header[i++] = (l2->vr << 5) | (l2->vs << 1);
+		p1 = (l2->vs - l2->va) % 8;
 		l2->vs = (l2->vs + 1) % 8;
 	}
-
-	nskb = skb_clone(skb, GFP_ATOMIC);
-	p1 = skb_headroom(nskb);
-	if (p1 >= i)
-		memcpy(skb_push(nskb, i), header, i);
-	else {
-		printk(KERN_WARNING
-		       "%s: L2 pull_iqueue skb header(%d/%d) too short\n",
-		       mISDNDevName4ch(&l2->ch), i, p1);
-		oskb = nskb;
-		nskb = mI_alloc_skb(oskb->len + i, GFP_ATOMIC);
-		if (!nskb) {
-			dev_kfree_skb(oskb);
-			printk(KERN_WARNING "%s: no skb mem in %s\n",
-			       mISDNDevName4ch(&l2->ch), __func__);
-			return;
-		}
-		memcpy(skb_put(nskb, i), header, i);
-		memcpy(skb_put(nskb, oskb->len), oskb->data, oskb->len);
-		dev_kfree_skb(oskb);
+	p1 = (p1 + l2->sow) % l2->window;
+	if (l2->windowar[p1]) {
+		printk(KERN_WARNING "%s: l2 try overwrite ack queue entry %d\n",
+		       mISDNDevName4ch(&l2->ch), p1);
+		dev_kfree_skb(l2->windowar[p1]);
 	}
+	l2->windowar[p1] = skb;
+	memcpy(skb_push(nskb, i), header, i);
 	l2down(l2, PH_DATA_REQ, l2_newid(l2), nskb);
 	test_and_clear_bit(FLG_ACK_PEND, &l2->flag);
 	if (!test_and_set_bit(FLG_T200_RUN, &l2->flag)) {