[PATCH] curl: Fix error path in curl_open()

[Hanna Czenczek <hreitz@redhat.com>]

g_hash_table_destroy() and g_hash_table_foreach_remove() (called by
curl_drop_all_sockets()) both require the table to be non-NULL, or will
print assertion failures (just print, no abort).

There are several paths in curl_open() that can lead to the out_noclean
label without s->sockets being allocated, so clean it only if it has
been allocated.

Example reproducer:
$ qemu-img info -f http ''
qemu-img: GLib: g_hash_table_foreach_remove: assertion 'hash_table != NULL' failed
qemu-img: GLib: g_hash_table_destroy: assertion 'hash_table != NULL' failed
qemu-img: Could not open '': http curl driver cannot handle the URL '' (does not start with 'http://')

Closes: https://gitlab.com/qemu-project/qemu/-/issues/1475
Suggested-by: Daniel P. Berrangé <berrange@redhat.com>
Signed-off-by: Hanna Czenczek <hreitz@redhat.com>
---
 block/curl.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/block/curl.c b/block/curl.c
index cbada22e9e..ba9977af5a 100644
--- a/block/curl.c
+++ b/block/curl.c
@@ -850,8 +850,10 @@ out_noclean:
     g_free(s->username);
     g_free(s->proxyusername);
     g_free(s->proxypassword);
-    curl_drop_all_sockets(s->sockets);
-    g_hash_table_destroy(s->sockets);
+    if (s->sockets) {
+        curl_drop_all_sockets(s->sockets);
+        g_hash_table_destroy(s->sockets);
+    }
     qemu_opts_del(opts);
     return -EINVAL;
 }
-- 
2.39.1