fit_load_fdt() passes @errp to fit_image_addr(), then recovers from
ENOENT failures.  Passing @errp is wrong, because it works only as
long as @errp is neither @error_fatal nor @error_abort.  Error
recovery dereferences @errp.  That's also wrong; see the big comment
in error.h.  Error recovery can leave *errp pointing to a freed
Error object.  Wrong, it must be null on success.  Messed up in
commit 3eb99edb48 "loader-fit: Wean off error_printf()".

No caller actually passes such values, or uses *errp on success.

Fix anyway: splice in a local Error *err, and error_propagate().

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <20191204093625.14836-8-armbru@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
---
 hw/core/loader-fit.c | 15 ++++++++-------
 1 file changed, 8 insertions(+), 7 deletions(-)

diff --git a/hw/core/loader-fit.c b/hw/core/loader-fit.c
index 953b16bc82..c465921b8f 100644
--- a/hw/core/loader-fit.c
+++ b/hw/core/loader-fit.c
@@ -178,11 +178,12 @@ static int fit_load_fdt(const struct fit_loader *ldr, const void *itb,
                         int cfg, void *opaque, const void *match_data,
                         hwaddr kernel_end, Error **errp)
 {
+    Error *err = NULL;
     const char *name;
     const void *data;
     const void *load_data;
     hwaddr load_addr;
-    int img_off, err;
+    int img_off;
     size_t sz;
     int ret;
 
@@ -197,13 +198,13 @@ static int fit_load_fdt(const struct fit_loader *ldr, const void *itb,
         return -EINVAL;
     }
 
-    err = fit_image_addr(itb, img_off, "load", &load_addr, errp);
-    if (err == -ENOENT) {
+    ret = fit_image_addr(itb, img_off, "load", &load_addr, &err);
+    if (ret == -ENOENT) {
         load_addr = ROUND_UP(kernel_end, 64 * KiB) + (10 * MiB);
-        error_free(*errp);
-    } else if (err) {
-        error_prepend(errp, "unable to read FDT load address from FIT: ");
-        ret = err;
+        error_free(err);
+    } else if (ret) {
+        error_propagate_prepend(errp, err,
+                                "unable to read FDT load address from FIT: ");
         goto out;
     }
 
-- 
2.21.0