linux-kernel - [2.6.19 patch] drivers/block/aoe/aoedev.c: fix NULL dereference

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Date:	Wed, 1 Nov 2006 01:40:25 +0100
From:	Adrian Bunk <bunk@...sta.de>
To:	"Ed L. Cashin" <ecashin@...aid.com>
Cc:	Alan Cox <alan@...hat.com>, Greg Kroah-Hartman <gregkh@...e.de>,
	linux-kernel@...r.kernel.org
Subject: [2.6.19 patch] drivers/block/aoe/aoedev.c: fix NULL dereference

This patch fixes a NULL dereference introduced by
commit e407a7f6cd143b3ab4eb3d7e1cf882e96b710eb5:

This quite unusual error handling through a switch introduces NULL 
dereferences if exactly one of the two k{c,z}alloc's failed.

That wouldn't be unfixable, but considering that the Linux kernel is not 
part of the obfuscated C contest (and silent fallthroughs in switches do 
not improve readability) I've converted it to a normal error handling.

The NULL dereference was spotted by the Coverity checker.

Signed-off-by: Adrian Bunk <bunk@...sta.de>

---

 drivers/block/aoe/aoedev.c |   46 ++++++++++++++++++-------------------
 1 file changed, 23 insertions(+), 23 deletions(-)

--- linux-2.6/drivers/block/aoe/aoedev.c.old	2006-10-31 23:56:46.000000000 +0100
+++ linux-2.6/drivers/block/aoe/aoedev.c	2006-11-01 00:23:49.000000000 +0100
@@ -64,30 +64,25 @@
 
 	d = kzalloc(sizeof *d, GFP_ATOMIC);
 	f = kcalloc(nframes, sizeof *f, GFP_ATOMIC);
- 	switch (!d || !f) {
- 	case 0:
- 		d->nframes = nframes;
- 		d->frames = f;
- 		e = f + nframes;
- 		for (; f<e; f++) {
- 			f->tag = FREETAG;
- 			f->skb = new_skb(ETH_ZLEN);
- 			if (!f->skb)
- 				break;
- 		}
- 		if (f == e)
- 			break;
- 		while (f > d->frames) {
- 			f--;
- 			dev_kfree_skb(f->skb);
- 		}
- 	default:
- 		if (f)
- 			kfree(f);
- 		if (d)
- 			kfree(d);
-		return NULL;
+
+ 	if (!d || !f)
+		goto out_err;
+
+	d->nframes = nframes;
+	d->frames = f;
+	e = f + nframes;
+	for (; f < e; f++) {
+		f->tag = FREETAG;
+		f->skb = new_skb(ETH_ZLEN);
+		if (!f->skb) {
+			while (f > d->frames) {
+				f--;
+				dev_kfree_skb(f->skb);
+			}
+			goto out_err;
+		}
 	}
+
 	INIT_WORK(&d->work, aoecmd_sleepwork, d);
 	spin_lock_init(&d->lock);
 	init_timer(&d->timer);
@@ -101,6 +96,11 @@
 	devlist = d;
 
 	return d;
+
+out_err:
+	kfree(f);
+	kfree(d);
+	return NULL;
 }
 
 void

-
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