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nbd: Check magic before doing anything else

PATCH In review Michal Feix 2 participants 2 messages Jul 16, 2006 – Jul 17, 2006

Subsystems (2)
Block layer Network block device (NBD)
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Michal Feix

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#0 lore raw

PATCH 1/1 nbd: Check magic before doing anything else

We should check magic sequence in reply packet before trying to find request with it's request handle. This also solves the problem with "Unexpected reply" message beeing logged, when packet with invalid magic is received.

Signed-off-by Michal Feix <[email protected]>

---

drivers/block/nbd.c +9 -7
diff -upr 2.6.18-rc2.orig/drivers/block/nbd.c 2.6.18-rc2/drivers/block/nbd.c
@@ -300,6 +300,15 @@ static struct request *nbd_read_stat(str
 				lo->disk->disk_name, result);
 		goto harderror;
 	}
+
+	if (ntohl(reply.magic) != NBD_REPLY_MAGIC) {
+		printk(KERN_ERR "%s: Wrong magic (0x%lx)\n",
+				lo->disk->disk_name,
+				(unsigned long)ntohl(reply.magic));
+		result = -EPROTO;
+		goto harderror;
+	}
+
 	req = nbd_find_request(lo, reply.handle);
 	if (unlikely(IS_ERR(req))) {
 		result = PTR_ERR(req);

@@ -312,13 +321,6 @@ static struct request *nbd_read_stat(str
 		goto harderror;
 	}
 
-	if (ntohl(reply.magic) != NBD_REPLY_MAGIC) {
-		printk(KERN_ERR "%s: Wrong magic (0x%lx)\n",
-				lo->disk->disk_name,
-				(unsigned long)ntohl(reply.magic));
-		result = -EPROTO;
-		goto harderror;
-	}
 	if (ntohl(reply.error)) {
 		printk(KERN_ERR "%s: Other side returned error (%d)\n",
 				lo->disk->disk_name, ntohl(reply.error));
#1 lore raw
Quoted 4 lines · Michal Feix

We should check magic sequence in reply packet before trying to find request with it's request handle. This also solves the problem with "Unexpected reply" message beeing logged, when packet with invalid magic is received.

Right. Again, we can't return NULL after pulling the request off the queue, so we better do this check first.

Andrew, these two look good to me.

Thanks,
Paul