From: Hani Benhabiles <kroosec@gmail.com>
Date: Sun, 18 May 2014 10:50:04 +0000 (+0100)
Subject: nbd: Don't export a block device with no medium.
X-Git-Tag: qemu-xen-4.5.0-rc1^2~30
X-Git-Url: http://xenbits.xensource.com/gitweb?a=commitdiff_plain;h=01083f16de92db2cab5a75cd9918a20df2b2fd2c;p=qemu-upstream-4.6-testing.git

nbd: Don't export a block device with no medium.

The device is exported with erroneous values and can't be read.

Before the patch:
$ sudo nbd-client localhost -p 10809 /dev/nbd0 -name floppy0
Negotiation: ..size = 17592186044415MB
bs=1024, sz=18446744073709547520 bytes

$ sudo mount /dev/nbd0 /mnt/tmp/
mount: block device /dev/nbd0 is write-protected, mounting read-only
mount: /dev/nbd0: can't read superblock

After the patch:
(qemu) nbd_server_add ide0-hd0
(qemu) nbd_server_add floppy0
Device 'floppy0' has no medium

Signed-off-by: Hani Benhabiles <kroosec@gmail.com>
Cc: qemu-stable@nongnu.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
(cherry picked from commit 60fe4fac22895576973e317d7148b084c31cc64c)
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>
---

diff --git a/blockdev-nbd.c b/blockdev-nbd.c
index 922cf5657..a700d52d7 100644
--- a/blockdev-nbd.c
+++ b/blockdev-nbd.c
@@ -91,6 +91,10 @@ void qmp_nbd_server_add(const char *device, bool has_writable, bool writable,
         error_set(errp, QERR_DEVICE_NOT_FOUND, device);
         return;
     }
+    if (!bdrv_is_inserted(bs)) {
+        error_set(errp, QERR_DEVICE_HAS_NO_MEDIUM, device);
+        return;
+    }
 
     if (!has_writable) {
         writable = false;