[PATCH 1/5] netfilter: nf_tables: reject new basechain after table flag update

Pablo Neira Ayuso
2024-04-08T21:20:53Z

commit 994209ddf4f430946f6247616b2e33d179243769 upstream.

When dormant flag is toggled, hooks are disabled in the commit phase by
iterating over current chains in table (existing and new).

The following configuration allows for an inconsistent state:

add table x
add chain x y { type filter hook input priority 0; }
add table x { flags dormant; }
add chain x w { type filter hook input priority 1; }

which triggers the following warning when trying to unregister chain w
which is already unregistered.

[ 127.322252] WARNING: CPU: 7 PID: 1211 at net/netfilter/core.c:50 1 __nf_unregister_net_hook+0x21a/0x260
[...]
[ 127.322519] Call Trace:
[ 127.322521] <TASK>
[ 127.322524] ? __warn+0x9f/0x1a0
[ 127.322531] ? __nf_unregister_net_hook+0x21a/0x260
[ 127.322537] ? report_bug+0x1b1/0x1e0
[ 127.322545] ? handle_bug+0x3c/0x70
[ 127.322552] ? exc_invalid_op+0x17/0x40
[ 127.322556] ? asm_exc_invalid_op+0x1a/0x20
[ 127.322563] ? kasan_save_free_info+0x3b/0x60
[ 127.322570] ? __nf_unregister_net_hook+0x6a/0x260
[ 127.322577] ? __nf_unregister_net_hook+0x21a/0x260
[ 127.322583] ? __nf_unregister_net_hook+0x6a/0x260
[ 127.322590] ? __nf_tables_unregister_hook+0x8a/0xe0 [nf_tables]
[ 127.322655] nft_table_disable+0x75/0xf0 [nf_tables]
[ 127.322717] nf_tables_commit+0x2571/0x2620 [nf_tables]

Fixes: 179d9ba5559a ("netfilter: nf_tables: fix table flag updates")
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
---
net/netfilter/nf_tables_api.c | 3 +++
1 file changed, 3 insertions(+)

diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
index 8d4472b127e4..fe7b66e04bdc 100644
--- a/net/netfilter/nf_tables_api.c
+++ b/net/netfilter/nf_tables_api.c
@@ -2225,6 +2225,9 @@ static int nf_tables_addchain(struct nft_ctx *ctx, u8 family, u8 genmask,
struct nft_stats __percpu *stats = NULL;
struct nft_chain_hook hook;

+ if (table->flags & __NFT_TABLE_F_UPDATE)
+ return -EINVAL;
+
if (flags & NFT_CHAIN_BINDING)
return -EOPNOTSUPP;

--
2.30.2