getentropy does not explicit_bzero if copyout fails

[Mateusz Guzik]

As the subject states. By the time the code gets to copyout, buf is
already populated. Clearing it only if copyout succeeds looks like a
braino, thus the following trivial proposal:

diff --git a/sys/dev/rnd.c b/sys/dev/rnd.c
index e33cb5fd7c0..fa876a950b9 100644
--- a/sys/dev/rnd.c
+++ b/sys/dev/rnd.c
@@ -932,9 +932,9 @@ sys_getentropy(struct proc *p, void *v, register_t
*retval)
        if (SCARG(uap, nbyte) > sizeof(buf))
                return (EIO);
        arc4random_buf(buf, SCARG(uap, nbyte));
-       if ((error = copyout(buf, SCARG(uap, buf), SCARG(uap, nbyte))) != 0)
-               return (error);
+       error = copyout(buf, SCARG(uap, buf), SCARG(uap, nbyte));
        explicit_bzero(buf, sizeof(buf));
-       retval[0] = 0;
-       return (0);
+       if (error == 0)
+               retval[0] = 0;
+       return (error);
 }


-- 
Mateusz Guzik <mjguzik gmail.com>