[PATCH 6.6 274/299] netfilter: nf_tables: register hooks last when adding new chain/flowtable

Greg Kroah-Hartman
2024-02-27T13:59:59Z

From: Pablo Neira Ayuso <pablo@netfilter.org>

[ Upstream commit d472e9853d7b46a6b094224d131d09ccd3a03daf ]

Register hooks last when adding chain/flowtable to ensure that packets do
not walk over datastructure that is being released in the error path
without waiting for the rcu grace period.

Fixes: 91c7b38dc9f0 ("netfilter: nf_tables: use new transaction infrastructure to handle chain")
Fixes: 3b49e2e94e6e ("netfilter: nf_tables: add flow table netlink frontend")
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/netfilter/nf_tables_api.c | 78 ++++++++++++++++++-----------------
1 file changed, 40 insertions(+), 38 deletions(-)

diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
index 40e8aa8343cc7..36fdce00bdab4 100644
--- a/net/netfilter/nf_tables_api.c
+++ b/net/netfilter/nf_tables_api.c
@@ -686,15 +686,16 @@ static int nft_delobj(struct nft_ctx *ctx, struct nft_object *obj)
return err;
}

-static int nft_trans_flowtable_add(struct nft_ctx *ctx, int msg_type,
- struct nft_flowtable *flowtable)
+static struct nft_trans *
+nft_trans_flowtable_add(struct nft_ctx *ctx, int msg_type,
+ struct nft_flowtable *flowtable)
{
struct nft_trans *trans;

trans = nft_trans_alloc(ctx, msg_type,
sizeof(struct nft_trans_flowtable));
if (trans == NULL)
- return -ENOMEM;
+ return ERR_PTR(-ENOMEM);

if (msg_type == NFT_MSG_NEWFLOWTABLE)
nft_activate_next(ctx->net, flowtable);
@@ -703,22 +704,22 @@ static int nft_trans_flowtable_add(struct nft_ctx *ctx, int msg_type,
nft_trans_flowtable(trans) = flowtable;
nft_trans_commit_list_add_tail(ctx->net, trans);

- return 0;
+ return trans;
}

static int nft_delflowtable(struct nft_ctx *ctx,
struct nft_flowtable *flowtable)
{
- int err;
+ struct nft_trans *trans;

- err = nft_trans_flowtable_add(ctx, NFT_MSG_DELFLOWTABLE, flowtable);
- if (err < 0)
- return err;
+ trans = nft_trans_flowtable_add(ctx, NFT_MSG_DELFLOWTABLE, flowtable);
+ if (IS_ERR(trans))
+ return PTR_ERR(trans);

nft_deactivate_next(ctx->net, flowtable);
nft_use_dec(&ctx->table->use);

- return err;
+ return 0;
}

static void __nft_reg_track_clobber(struct nft_regs_track *track, u8 dreg)
@@ -2506,19 +2507,15 @@ static int nf_tables_addchain(struct nft_ctx *ctx, u8 family, u8 genmask,
RCU_INIT_POINTER(chain->blob_gen_0, blob);
RCU_INIT_POINTER(chain->blob_gen_1, blob);

- err = nf_tables_register_hook(net, table, chain);
- if (err < 0)
- goto err_destroy_chain;
-
if (!nft_use_inc(&table->use)) {
err = -EMFILE;
- goto err_use;
+ goto err_destroy_chain;
}

trans = nft_trans_chain_add(ctx, NFT_MSG_NEWCHAIN);
if (IS_ERR(trans)) {
err = PTR_ERR(trans);
- goto err_unregister_hook;
+ goto err_trans;
}

nft_trans_chain_policy(trans) = NFT_CHAIN_POLICY_UNSET;
@@ -2526,17 +2523,22 @@ static int nf_tables_addchain(struct nft_ctx *ctx, u8 family, u8 genmask,
nft_trans_chain_policy(trans) = policy;

err = nft_chain_add(table, chain);
- if (err < 0) {
- nft_trans_destroy(trans);
- goto err_unregister_hook;
- }
+ if (err < 0)
+ goto err_chain_add;
+
+ /* This must be LAST to ensure no packets are walking over this chain. */
+ err = nf_tables_register_hook(net, table, chain);
+ if (err < 0)
+ goto err_register_hook;

return 0;

-err_unregister_hook:
+err_register_hook:
+ nft_chain_del(chain);
+err_chain_add:
+ nft_trans_destroy(trans);
+err_trans:
nft_use_dec_restore(&table->use);
-err_use:
- nf_tables_unregister_hook(net, table, chain);
err_destroy_chain:
nf_tables_chain_destroy(ctx);

@@ -8334,9 +8336,9 @@ static int nf_tables_newflowtable(struct sk_buff *skb,
u8 family = info->nfmsg->nfgen_family;
const struct nf_flowtable_type *type;
struct nft_flowtable *flowtable;
- struct nft_hook *hook, *next;
struct net *net = info->net;
struct nft_table *table;
+ struct nft_trans *trans;
struct nft_ctx ctx;
int err;

@@ -8416,34 +8418,34 @@ static int nf_tables_newflowtable(struct sk_buff *skb,
err = nft_flowtable_parse_hook(&ctx, nla, &flowtable_hook, flowtable,
extack, true);
if (err < 0)
- goto err4;
+ goto err_flowtable_parse_hooks;

list_splice(&flowtable_hook.list, &flowtable->hook_list);
flowtable->data.priority = flowtable_hook.priority;
flowtable->hooknum = flowtable_hook.num;

+ trans = nft_trans_flowtable_add(&ctx, NFT_MSG_NEWFLOWTABLE, flowtable);
+ if (IS_ERR(trans)) {
+ err = PTR_ERR(trans);
+ goto err_flowtable_trans;
+ }
+
+ /* This must be LAST to ensure no packets are walking over this flowtable. */
err = nft_register_flowtable_net_hooks(ctx.net, table,
&flowtable->hook_list,
flowtable);
- if (err < 0) {
- nft_hooks_destroy(&flowtable->hook_list);
- goto err4;
- }
-
- err = nft_trans_flowtable_add(&ctx, NFT_MSG_NEWFLOWTABLE, flowtable);
if (err < 0)
- goto err5;
+ goto err_flowtable_hooks;

list_add_tail_rcu(&flowtable->list, &table->flowtables);

return 0;
-err5:
- list_for_each_entry_safe(hook, next, &flowtable->hook_list, list) {
- nft_unregister_flowtable_hook(net, flowtable, hook);
- list_del_rcu(&hook->list);
- kfree_rcu(hook, rcu);
- }
-err4:
+
+err_flowtable_hooks:
+ nft_trans_destroy(trans);
+err_flowtable_trans:
+ nft_hooks_destroy(&flowtable->hook_list);
+err_flowtable_parse_hooks:
flowtable->data.type->free(&flowtable->data);
err3:
module_put(type->owner);
--
2.43.0