[PATCH 5.15 072/139] netfilter: nf_tables: fix memory leak during stateful obj update

Greg Kroah-Hartman
2022-02-28T17:54:12Z

From: Florian Westphal <fw@strlen.de>

commit dad3bdeef45f81a6e90204bcc85360bb76eccec7 upstream.

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@riseup.net>
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/netfilter/nf_tables_api.c | 13 +++++++++----
1 file changed, 9 insertions(+), 4 deletions(-)

--- a/net/netfilter/nf_tables_api.c
+++ b/net/netfilter/nf_tables_api.c
@@ -6535,12 +6535,15 @@ static int nf_tables_updobj(const struct
{
struct nft_object *newobj;
struct nft_trans *trans;
- int err;
+ int err = -ENOMEM;
+
+ 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)) {
@@ -6557,6 +6560,8 @@ static int nf_tables_updobj(const struct

err_free_trans:
kfree(trans);
+err_trans:
+ module_put(type->owner);
return err;
}

@@ -8169,7 +8174,7 @@ static void nft_obj_commit_update(struct
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)
@@ -8914,7 +8919,7 @@ static int __nf_tables_abort(struct net
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--;