[PATCH] qemu_block: Validate number of hosts for iSCSI disk device

[Rayhan Faizel <rayhan.faizel@xxxxxxxxx>]

An iSCSI device with zero hosts will result in a segmentation fault. This patch
adds a check for the number of hosts, which must be one in the case of iSCSI.

Minimal reproducing XML:

<domain type='qemu'>
    <name>MyGuest</name>
    <uuid>4dea22b3-1d52-d8f3-2516-782e98ab3fa0</uuid>
    <os>
        <type arch='x86_64'>hvm</type>
    </os>
    <memory>4096</memory>
    <devices>
        <disk type='network'>
            <source name='dummy' protocol='iscsi'/>
            <target dev='vda'/>
        </disk>
    </devices>
</domain>

Signed-off-by: Rayhan Faizel <rayhan.faizel@xxxxxxxxx>
---
This crashing XML was detected by the WIP fuzzer which is being developed
as part of Google Summer of Code 2024.

 src/qemu/qemu_block.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/src/qemu/qemu_block.c b/src/qemu/qemu_block.c
index 738b72d7ea..d6cdf521c4 100644
--- a/src/qemu/qemu_block.c
+++ b/src/qemu/qemu_block.c
@@ -602,6 +602,12 @@ qemuBlockStorageSourceGetISCSIProps(virStorageSource *src,
      * }
      */
 
+    if (src->nhosts != 1) {
+        virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
+                       _("iSCSI protocol accepts only one host"));
+        return NULL;
+    }
+
     target = g_strdup(src->path);
 
     /* Separate the target and lun */
-- 
2.34.1