[PATCH 1/2] xen/console: fix error handling in xen_console_device_create()

[Roger Pau Monne <roger.pau@xxxxxxxxxx>]

The usage of error_prepend() in some of the error contexts of
xen_console_device_create() is incorrect, as `errp` hasn't been initialized.
This leads to the following segmentation fault on error paths resulting from
xenstore reads:

Program terminated with signal SIGSEGV, Segmentation fault.
Address not mapped to object.
    fmt=0x15c4dfeade42 "failed to read console device type: ", 
ap=0x15cd0165ab50)
    at ../qemu-xen-dir-remote/util/error.c:142
142         g_string_append(newmsg, (*errp)->msg);
[...]
(gdb) bt
    (errp=0x15cd0165ae10, fmt=0x15c4dfeade42 "failed to read console device 
type: ", ap=0x15cd0165ab50) at ../qemu-xen-dir-remote/util/error.c:142
    (errp=0x15cd0165ae10, fmt=0x15c4dfeade42 "failed to read console device 
type: ")
    at ../qemu-xen-dir-remote/util/error.c:152
    (backend=0x43944de00660, opts=0x43944c929000, errp=0x15cd0165ae10)
    at ../qemu-xen-dir-remote/hw/char/xen_console.c:555

Replace usages of error_prepend() with error_setg() where appropriate.

Fixes: 9b7737469080 ('hw/xen: update Xen console to XenDevice model')
Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
---
Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>
Cc: Anthony PERARD <anthony@xxxxxxxxxxxxxx>
Cc: Paul Durrant <paul@xxxxxxx>
Cc: "Edgar E. Iglesias" <edgar.iglesias@xxxxxxxxx>
Cc: "Marc-André Lureau" <marcandre.lureau@xxxxxxxxxx>
Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Cc: xen-devel@xxxxxxxxxxxxxxxxxxxx
---
 hw/char/xen_console.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/hw/char/xen_console.c b/hw/char/xen_console.c
index ef0c2912efa1..af706c7ef440 100644
--- a/hw/char/xen_console.c
+++ b/hw/char/xen_console.c
@@ -551,7 +551,7 @@ static void xen_console_device_create(XenBackendInstance 
*backend,
     }
 
     if (xs_node_scanf(xsh, XBT_NULL, fe, "type", errp, "%ms", &type) != 1) {
-        error_prepend(errp, "failed to read console device type: ");
+        error_setg(errp, "failed to read console device type: ");
         goto fail;
     }
 
@@ -582,7 +582,7 @@ static void xen_console_device_create(XenBackendInstance 
*backend,
     } else if (number) {
         cd = serial_hd(number);
         if (!cd) {
-            error_prepend(errp, "console: No serial device #%ld found: ",
+            error_setg(errp, "console: No serial device #%ld found: ",
                           number);
             goto fail;
         }
-- 
2.46.0