On Mon, Feb 21, 2022 at 11:59:22AM +0100, Florian Westphal wrote:
> Florian Westphal <fw@xxxxxxxxx> wrote:
> > Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx> wrote:
> > > On Sun, Feb 20, 2022 at 12:18:50PM +0100, Florian Westphal wrote:
> > > > stateful objects can be updated from the control plane.
> > > > The transaction logic allocates a temporary object for this purpose.
> > > >
> > > > This object has to be released via nft_obj_destroy, not kfree, since
> > > > the ->init function was called and it can have side effects beyond
> > > > memory allocation.
> > > >
> > > > Unlike normal NEWOBJ path, the objects module refcount isn't
> > > > incremented, so add nft_newobj_destroy and use that.
> > >
> > > Probably this? .udata and .key is NULL for the update path so kfree
> > > should be fine.
> >
> > Yes, that works too.
> >
> > We could also ...
> >
> > > - module_put(obj->ops->type->owner);
> > > + /* nf_tables_updobj does not increment module refcount */
> > > + if (!update)
> > > + module_put(obj->ops->type->owner);
> > > +
> >
> > Increment the refcount for update case as well to avoid the special
> > case?
Yes, I also though of this one. I prefer this approach indeed to
consolidate this path.
Would you test and submit v3?
Thanks!
> Untested:
>
> diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
> index 3081c4399f10..49060f281342 100644
> --- a/net/netfilter/nf_tables_api.c
> +++ b/net/netfilter/nf_tables_api.c
> @@ -6553,10 +6553,13 @@ static int nf_tables_updobj(const struct nft_ctx *ctx,
> struct nft_trans *trans;
> int err;
>
> + if (!try_module_get(type->owner))
> + return -ENOENT;
> +
> trans = nft_trans_alloc(ctx, NFT_MSG_NEWOBJ,
> sizeof(struct nft_trans_obj));
> if (!trans)
> - return -ENOMEM;
> + goto err_trans;
>
> newobj = nft_obj_init(ctx, type, attr);
> if (IS_ERR(newobj)) {
> @@ -6573,6 +6576,8 @@ static int nf_tables_updobj(const struct nft_ctx *ctx,
>
> err_free_trans:
> kfree(trans);
> +err_trans:
> + module_put(type->owner);
> return err;
> }
>
> @@ -8185,7 +8190,7 @@ static void nft_obj_commit_update(struct nft_trans *trans)
> if (obj->ops->update)
> obj->ops->update(obj, newobj);
>
> - kfree(newobj);
> + nft_obj_destroy(&trans->ctx, newobj);
> }
>
> static void nft_commit_release(struct nft_trans *trans)
> @@ -8976,7 +8981,7 @@ static int __nf_tables_abort(struct net *net, enum nfnl_abort_action action)
> break;
> case NFT_MSG_NEWOBJ:
> if (nft_trans_obj_update(trans)) {
> - kfree(nft_trans_obj_newobj(trans));
> + nft_obj_destroy(&trans->ctx, nft_trans_obj_newobj(trans));
> nft_trans_destroy(trans);
> } else {
> trans->ctx.table->use--;
