On Fri, Mar 20, 2020 at 08:23:57AM -0700, Yonghong Song wrote: > > > On 3/20/20 2:48 AM, Greg Kroah-Hartman wrote: > > For the bpf syscall, we are relying on the compiler to properly zero out > > the bpf_attr union that we copy userspace data into. Unfortunately that > > doesn't always work properly, padding and other oddities might not be > > correctly zeroed, and in some tests odd things have been found when the > > stack is pre-initialized to other values. > > Maybe add more contexts about the failure itself so it could be clear > why we need this patch. I didn't have the full details, I think Maciej has them though. > As far as I know from the link below, the failure happens in > CHECK_ATTR() which checks any unused *area* for a particular subcommand > must be 0, and this patch tries to provide this guarantee beyond > area beyond min(uattr_size, sizeof(attr)). That macro also will get tripped up if padding is not zeroed out as well, so this is good to fix up. thanks for the review. greg k-h
