[PULL,22/28] x86: Fix x86_cpu_new() error handling

Commit Message

Markus Armbruster July 2, 2020, 11:09 a.m. UTC

The Error ** argument must be NULL, &error_abort, &error_fatal, or a
pointer to a variable containing NULL.  Passing an argument of the
latter kind twice without clearing it in between is wrong: if the
first call sets an error, it no longer points to NULL for the second
call.

x86_cpu_new() is wrong that way: it passes &local_err to
object_property_set_uint() without checking it, and then to
qdev_realize().  If both fail, we'll trip error_setv()'s assertion.
To assess the bug's impact, we'd need to figure out how to make both
calls fail.  Too much work for ignorant me, sorry.

Fix by checking for failure right away.

Cc: Igor Mammedov <[e-mail]>
Cc: Paolo Bonzini <[e-mail]>
Cc: Richard Henderson <[e-mail]>
Cc: Eduardo Habkost <[e-mail]>
Signed-off-by: Markus Armbruster <[e-mail]>
Message-Id: <[e-mail]>
Reviewed-by: Paolo Bonzini <[e-mail]>
---
 hw/i386/x86.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

Patch

diff --git a/hw/i386/x86.c b/hw/i386/x86.c
index 34229b45c7..93f7371a56 100644
--- a/hw/i386/x86.c
+++ b/hw/i386/x86.c
@@ -118,14 +118,16 @@  uint32_t x86_cpu_apic_id_from_index(X86MachineState *x86ms,
 
 void x86_cpu_new(X86MachineState *x86ms, int64_t apic_id, Error **errp)
 {
-    Object *cpu = NULL;
     Error *local_err = NULL;
-
-    cpu = object_new(MACHINE(x86ms)->cpu_type);
+    Object *cpu = object_new(MACHINE(x86ms)->cpu_type);
 
     object_property_set_uint(cpu, apic_id, "apic-id", &local_err);
+    if (local_err) {
+        goto out;
+    }
     qdev_realize(DEVICE(cpu), NULL, &local_err);
 
+out:
     object_unref(cpu);
     error_propagate(errp, local_err);
 }