[PATCH] nbd: Check magic before doing anything else

[PATCH] nbd: Check magic before doing anything else

[Michal Feix]

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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 <michal@feix.cz>

---


[-- Attachment #2: nbd.c.magic-check.diff --]
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diff -upr 2.6.18-rc2.orig/drivers/block/nbd.c 2.6.18-rc2/drivers/block/nbd.c
--- 2.6.18-rc2.orig/drivers/block/nbd.c	2006-07-16 14:34:09.106878500 +0200
+++ 2.6.18-rc2/drivers/block/nbd.c	2006-07-16 14:48:59.000000000 +0200
@@ -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));

Re: [PATCH] nbd: Check magic before doing anything else

[Paul Clements]

Michal Feix wrote:
> 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