On Wed, Aug 17, 2022, at 12:34 PM, Florian Westphal wrote: > Daniel Xu <dxu@xxxxxxxxx> wrote: >> On Mon, Aug 15, 2022, at 4:40 PM, Florian Westphal wrote: >> > Toke Høiland-Jørgensen <toke@xxxxxxxxxx> wrote: >> >> > Support direct writes to nf_conn:mark from TC and XDP prog types. This >> >> > is useful when applications want to store per-connection metadata. This >> >> > is also particularly useful for applications that run both bpf and >> >> > iptables/nftables because the latter can trivially access this metadata. >> >> > >> >> > One example use case would be if a bpf prog is responsible for advanced >> >> > packet classification and iptables/nftables is later used for routing >> >> > due to pre-existing/legacy code. >> >> > >> >> > Signed-off-by: Daniel Xu <dxu@xxxxxxxxx> >> >> >> >> Didn't we agree the last time around that all field access should be >> >> using helper kfuncs instead of allowing direct writes to struct nf_conn? >> > >> > I don't see why ct->mark needs special handling. >> > >> > It might be possible we need to change accesses on nf/tc side to use >> > READ/WRITE_ONCE though. >> >> I reviewed some of the LKMM literature and I would concur that >> READ/WRITE_ONCE() is necessary. Especially after this patchset. >> >> However, it's unclear to me if this is a latent issue. IOW: is reading >> ct->mark protected by a lock? I only briefly looked but it doesn't >> seem like it. > > No, its not protected by a lock. READ/WRITE_ONCE is unrelated to your > patchset, this is a pre-existing "bug". Thanks for confirming. Since it's pre-existing I will send out a followup patchset then. Thanks, Daniel
