syzbot is reporting underflow of nft_counters_enabled counter at
nf_tables_addchain() [1], for commit 43eb8949cfdffa76 ("netfilter:
nf_tables: do not leave chain stats enabled on error") missed that
nf_tables_chain_destroy() after nft_basechain_init() in the error path of
nf_tables_addchain() decrements the counter because nft_basechain_init()
makes nft_is_base_chain() return true by setting NFT_CHAIN_BASE flag.
Increment the counter immediately after returning from
nft_basechain_init().
Link: https://syzkaller.appspot.com/bug?extid=b5d82a651b71cd8a75ab [1]
Reported-by: syzbot <syzbot+b5d82a651b71cd8a75ab@xxxxxxxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
Tested-by: syzbot <syzbot+b5d82a651b71cd8a75ab@xxxxxxxxxxxxxxxxxxxxxxxxx>
Fixes: 43eb8949cfdffa76 ("netfilter: nf_tables: do not leave chain stats enabled on error")
---
net/netfilter/nf_tables_api.c | 7 +++----
1 file changed, 3 insertions(+), 4 deletions(-)
diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
index 816052089b33..e062754dc6cc 100644
--- a/net/netfilter/nf_tables_api.c
+++ b/net/netfilter/nf_tables_api.c
@@ -2197,7 +2197,6 @@ static int nf_tables_addchain(struct nft_ctx *ctx, u8 family, u8 genmask,
struct netlink_ext_ack *extack)
{
const struct nlattr * const *nla = ctx->nla;
- struct nft_stats __percpu *stats = NULL;
struct nft_table *table = ctx->table;
struct nft_base_chain *basechain;
struct net *net = ctx->net;
@@ -2212,6 +2211,7 @@ static int nf_tables_addchain(struct nft_ctx *ctx, u8 family, u8 genmask,
return -EOVERFLOW;
if (nla[NFTA_CHAIN_HOOK]) {
+ struct nft_stats __percpu *stats = NULL;
struct nft_chain_hook hook;
if (flags & NFT_CHAIN_BINDING)
@@ -2245,6 +2245,8 @@ static int nf_tables_addchain(struct nft_ctx *ctx, u8 family, u8 genmask,
kfree(basechain);
return err;
}
+ if (stats)
+ static_branch_inc(&nft_counters_enabled);
} else {
if (flags & NFT_CHAIN_BASE)
return -EINVAL;
@@ -2319,9 +2321,6 @@ static int nf_tables_addchain(struct nft_ctx *ctx, u8 family, u8 genmask,
goto err_unregister_hook;
}
- if (stats)
- static_branch_inc(&nft_counters_enabled);
-
table->use++;
return 0;
--
2.18.4
