Jesper Dangaard Brouer wrote: > Clearing memory of tail when grow happens, because it is too easy > to write a XDP_PASS program that extend the tail, which expose > this memory to users that can run tcpdump. > > Signed-off-by: Jesper Dangaard Brouer <brouer@xxxxxxxxxx> > --- Hi Jesper, Thanks for the series any idea what the cost of doing this is? If you have some data I would be curious to know a baseline measurment, a grow with memset, then a grow with memset. I'm guess this can be relatively expensive? > net/core/filter.c | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/net/core/filter.c b/net/core/filter.c > index 5e9c387f74eb..889d96a690c2 100644 > --- a/net/core/filter.c > +++ b/net/core/filter.c > @@ -3442,6 +3442,10 @@ BPF_CALL_2(bpf_xdp_adjust_tail, struct xdp_buff *, xdp, int, offset) > if (unlikely(data_end < xdp->data + ETH_HLEN)) > return -EINVAL; > > + /* Clear memory area on grow, can contain uninit kernel memory */ > + if (offset > 0) > + memset(xdp->data_end, 0, offset); > + > xdp->data_end = data_end; > > return 0; > >
