We are *not* guaranteed that anything past the terminating NUL is mapped (let alone initialized with anything sane). Signed-off-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx> --- diff --git a/mm/memcontrol-v1.c b/mm/memcontrol-v1.c index 2aeea4d8bf8e..417c96f2da28 100644 --- a/mm/memcontrol-v1.c +++ b/mm/memcontrol-v1.c @@ -1842,9 +1842,12 @@ static ssize_t memcg_write_event_control(struct kernfs_open_file *of, buf = endp + 1; cfd = simple_strtoul(buf, &endp, 10); - if ((*endp != ' ') && (*endp != '\0')) + if (*endp == '\0') + buf = endp; + else if (*endp == ' ') + buf = endp + 1; + else return -EINVAL; - buf = endp + 1; event = kzalloc(sizeof(*event), GFP_KERNEL); if (!event)