From: Florian Westphal fw@strlen.de
commit b04df3da1b5c6f6dc7cdccc37941740c078c4043 upstream.
nf_tables_chain_destroy can sleep, it can't be used from call_rcu callbacks.
Moreover, nf_tables_rule_release() is only safe for error unwinding, while transaction mutex is held and the to-be-desroyed rule was not exposed to either dataplane or dumps, as it deactives+frees without the required synchronize_rcu() in-between.
nft_rule_expr_deactivate() callbacks will change ->use counters of other chains/sets, see e.g. nft_lookup .deactivate callback, these must be serialized via transaction mutex.
Also add a few lockdep asserts to make this more explicit.
Calling synchronize_rcu() isn't ideal, but fixing this without is hard and way more intrusive. As-is, we can get:
WARNING: .. net/netfilter/nf_tables_api.c:5515 nft_set_destroy+0x.. Workqueue: events nf_tables_trans_destroy_work RIP: 0010:nft_set_destroy+0x3fe/0x5c0 Call Trace: <TASK> nf_tables_trans_destroy_work+0x6b7/0xad0 process_one_work+0x64a/0xce0 worker_thread+0x613/0x10d0
In case the synchronize_rcu becomes an issue, we can explore alternatives.
One way would be to allocate nft_trans_rule objects + one nft_trans_chain object, deactivate the rules + the chain and then defer the freeing to the nft destroy workqueue. We'd still need to keep the synchronize_rcu path as a fallback to handle -ENOMEM corner cases though.
Reported-by: syzbot+b26935466701e56cfdc2@syzkaller.appspotmail.com Closes: https://lore.kernel.org/all/67478d92.050a0220.253251.0062.GAE@google.com/T/ Fixes: c03d278fdf35 ("netfilter: nf_tables: wait for rcu grace period on net_device removal") Signed-off-by: Florian Westphal fw@strlen.de Signed-off-by: Pablo Neira Ayuso pablo@netfilter.org --- include/net/netfilter/nf_tables.h | 3 --- net/netfilter/nf_tables_api.c | 31 ++++++++++++++----------------- 2 files changed, 14 insertions(+), 20 deletions(-)
diff --git a/include/net/netfilter/nf_tables.h b/include/net/netfilter/nf_tables.h index 566370938939..92551a765a44 100644 --- a/include/net/netfilter/nf_tables.h +++ b/include/net/netfilter/nf_tables.h @@ -899,7 +899,6 @@ struct nft_chain { u8 flags:6, genmask:2; char *name; - struct rcu_head rcu_head;
/* Only used during control plane commit phase: */ struct nft_rule **rules_next; @@ -1016,7 +1015,6 @@ static inline void nft_use_inc_restore(u32 *use) * @sets: sets in the table * @objects: stateful objects in the table * @flowtables: flow tables in the table - * @net: netnamespace this table belongs to * @hgenerator: handle generator state * @handle: table handle * @use: number of chain references to this table @@ -1032,7 +1030,6 @@ struct nft_table { struct list_head sets; struct list_head objects; struct list_head flowtables; - possible_net_t net; u64 hgenerator; u64 handle; u32 use; diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c index 2d015fcf8d8d..9e20fb759cb8 100644 --- a/net/netfilter/nf_tables_api.c +++ b/net/netfilter/nf_tables_api.c @@ -1109,7 +1109,6 @@ static int nf_tables_newtable(struct net *net, struct sock *nlsk, INIT_LIST_HEAD(&table->sets); INIT_LIST_HEAD(&table->objects); INIT_LIST_HEAD(&table->flowtables); - write_pnet(&table->net, net); table->family = family; table->flags = flags; table->handle = ++table_handle; @@ -2824,6 +2823,8 @@ static void nf_tables_rule_destroy(const struct nft_ctx *ctx, static void nf_tables_rule_release(const struct nft_ctx *ctx, struct nft_rule *rule) { + lockdep_commit_lock_is_held(ctx->net); + nft_rule_expr_deactivate(ctx, rule, NFT_TRANS_RELEASE); nf_tables_rule_destroy(ctx, rule); } @@ -4172,6 +4173,8 @@ void nf_tables_deactivate_set(const struct nft_ctx *ctx, struct nft_set *set, struct nft_set_binding *binding, enum nft_trans_phase phase) { + lockdep_commit_lock_is_held(ctx->net); + switch (phase) { case NFT_TRANS_PREPARE_ERROR: nft_set_trans_unbind(ctx, set); @@ -8228,19 +8231,6 @@ static void __nft_release_basechain_now(struct nft_ctx *ctx) nf_tables_chain_destroy(ctx->chain); }
-static void nft_release_basechain_rcu(struct rcu_head *head) -{ - struct nft_chain *chain = container_of(head, struct nft_chain, rcu_head); - struct nft_ctx ctx = { - .family = chain->table->family, - .chain = chain, - .net = read_pnet(&chain->table->net), - }; - - __nft_release_basechain_now(&ctx); - put_net(ctx.net); -} - int __nft_release_basechain(struct nft_ctx *ctx) { struct nft_rule *rule; @@ -8255,11 +8245,18 @@ int __nft_release_basechain(struct nft_ctx *ctx) nft_chain_del(ctx->chain); nft_use_dec(&ctx->table->use);
- if (maybe_get_net(ctx->net)) - call_rcu(&ctx->chain->rcu_head, nft_release_basechain_rcu); - else + if (!maybe_get_net(ctx->net)) { __nft_release_basechain_now(ctx); + return 0; + } + + /* wait for ruleset dumps to complete. Owning chain is no longer in + * lists, so new dumps can't find any of these rules anymore. + */ + synchronize_rcu();
+ __nft_release_basechain_now(ctx); + put_net(ctx->net); return 0; } EXPORT_SYMBOL_GPL(__nft_release_basechain);