vmspawn: check overflow earlier

Follow-up for 862c68a914ab4561d83875e58e05dcf65cb4a551.
Fixes CID#1550749.

diff --git a/src/vmspawn/vmspawn.c b/src/vmspawn/vmspawn.c
index 8fad195abcdf8e4aa1d337f7151c71fb61a7e977..030efbdb23fc40aca9f0aa3d3cee10a7f50f7d0a 100644 (file)
--- a/src/vmspawn/vmspawn.c
+++ b/src/vmspawn/vmspawn.c
@@ -626,10 +626,10 @@ static int read_vsock_notify(NotifyConnectionData *d, int fd) {
                 if (n == 0) /* We hit EOF! Let's parse this */
                         break;
 
-                d->full += n;
-
-                if (d->full >= sizeof(d->buffer))
+                if ((size_t) n >= sizeof(d->buffer) - d->full)
                         return log_error_errno(SYNTHETIC_ERRNO(EBADMSG), "Received notify message exceeded maximum size.");
+
+                d->full += n;
         }
 
         /* We reached EOF, now parse the thing */