[PATCH nf-next] netfilter: move nf_tables base hook annotation to init helper

[PATCH nf-next] netfilter: move nf_tables base hook annotation to init helper

[Florian Westphal]

coverity scanner says:
2187  if (nft_is_base_chain(chain)) {
vvv   CID 1505166:  Memory - corruptions  (UNINIT)
vvv   Using uninitialized value "basechain".
2188  basechain->ops.hook_ops_type = NF_HOOK_OP_NF_TABLES;

... I don't see how nft_is_base_chain() can evaluate to true
while basechain pointer is garbage.

However, it seems better to place the NF_HOOK_OP_NF_TABLES annotation
in nft_basechain_hook_init() instead.

Reported-by: coverity-bot <keescook+coverity-bot@chromium.org>
Addresses-Coverity-ID: 1505166 ("Memory - corruptions")
Fixes: 65b8b7bfc5284f ("netfilter: annotate nf_tables base hook ops")
Signed-off-by: Florian Westphal <fw@strlen.de>
---
 net/netfilter/nf_tables_api.c | 15 +++++++--------
 1 file changed, 7 insertions(+), 8 deletions(-)

diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
index 3fe052710381..6a350b38d85d 100644
--- a/net/netfilter/nf_tables_api.c
+++ b/net/netfilter/nf_tables_api.c
@@ -2001,11 +2001,12 @@ static void nft_basechain_hook_init(struct nf_hook_ops *ops, u8 family,
 				    const struct nft_chain_hook *hook,
 				    struct nft_chain *chain)
 {
-	ops->pf		= family;
-	ops->hooknum	= hook->num;
-	ops->priority	= hook->priority;
-	ops->priv	= chain;
-	ops->hook	= hook->type->hooks[ops->hooknum];
+	ops->pf			= family;
+	ops->hooknum		= hook->num;
+	ops->priority		= hook->priority;
+	ops->priv		= chain;
+	ops->hook		= hook->type->hooks[ops->hooknum];
+	ops->hook_ops_type	= NF_HOOK_OP_NF_TABLES;
 }
 
 static int nft_basechain_init(struct nft_base_chain *basechain, u8 family,
@@ -2172,10 +2173,8 @@ static int nf_tables_addchain(struct nft_ctx *ctx, u8 family, u8 genmask,
 	}
 
 	nft_trans_chain_policy(trans) = NFT_CHAIN_POLICY_UNSET;
-	if (nft_is_base_chain(chain)) {
-		basechain->ops.hook_ops_type = NF_HOOK_OP_NF_TABLES;
+	if (nft_is_base_chain(chain))
 		nft_trans_chain_policy(trans) = policy;
-	}
 
 	err = nft_chain_add(table, chain);
 	if (err < 0) {
-- 
2.31.1

Re: [PATCH nf-next] netfilter: move nf_tables base hook annotation to init helper

[Pablo Neira Ayuso]

On Tue, Jun 08, 2021 at 11:06:07PM +0200, Florian Westphal wrote:
> coverity scanner says:
> 2187  if (nft_is_base_chain(chain)) {
> vvv   CID 1505166:  Memory - corruptions  (UNINIT)
> vvv   Using uninitialized value "basechain".
> 2188  basechain->ops.hook_ops_type = NF_HOOK_OP_NF_TABLES;
> 
> ... I don't see how nft_is_base_chain() can evaluate to true
> while basechain pointer is garbage.
> 
> However, it seems better to place the NF_HOOK_OP_NF_TABLES annotation
> in nft_basechain_hook_init() instead.

Applied, thanks.