On Mon, 21 Feb 2022 17:17:57 +0100 Pablo Neira Ayuso wrote:
> From: Florian Westphal <fw@xxxxxxxxx>
>
> stateful objects can be updated from the control plane.
> The transaction logic allocates a temporary object for this purpose.
>
> The ->init function was called for this object, so plain kfree() leaks
> resources. We must call ->destroy function of the object.
>
> nft_obj_destroy does this, but it also decrements the module refcount,
> but the update path doesn't increment it.
>
> To avoid special-casing the update object release, do module_get for
> the update case too and release it via nft_obj_destroy().
>
> Fixes: d62d0ba97b58 ("netfilter: nf_tables: Introduce stateful object update operation")
> Cc: Fernando Fernandez Mancera <ffmancera@xxxxxxxxxx>
> Signed-off-by: Florian Westphal <fw@xxxxxxxxx>
> Signed-off-by: Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx>
> ---
> net/netfilter/nf_tables_api.c | 11 ++++++++---
> 1 file changed, 8 insertions(+), 3 deletions(-)
>
> 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--;
net/netfilter/nf_tables_api.c:6561:6: warning: variable 'err' is used uninitialized whenever 'if' condition is true [-Wsometimes-uninitialized]
if (!trans)
^~~~~~
net/netfilter/nf_tables_api.c:6581:9: note: uninitialized use occurs here
return err;
^~~
net/netfilter/nf_tables_api.c:6561:2: note: remove the 'if' if its condition is always false
if (!trans)
^~~~~~~~~~~
net/netfilter/nf_tables_api.c:6554:9: note: initialize the variable 'err' to silence this warning
int err;
^
= 0
