[PATCH nft] Check for NULL netlink attributes

[Davide Ornaghi <d.ornaghi97@xxxxxxxxx>]

Payload and meta nftables exprs can be embedded into inner exprs via
nft_expr_inner_parse, which doesn't check for NULL netlink attributes,
unlike other exprs passing through select_ops.
Add the missing checks to nft_meta_inner_init and nft_payload_inner_init
to prevent dereferencing NULL pointers and eventually causing UAF reads
on commit_mutex.

Signed-off-by: Davide Ornaghi <d.ornaghi97@xxxxxxxxx>
---
 net/netfilter/nft_meta.c    | 2 ++
 net/netfilter/nft_payload.c | 3 +++
 2 files changed, 5 insertions(+)

diff --git a/net/netfilter/nft_meta.c b/net/netfilter/nft_meta.c
index ba0d3683a..e2893077b 100644
--- a/net/netfilter/nft_meta.c
+++ b/net/netfilter/nft_meta.c
@@ -839,6 +839,8 @@ static int nft_meta_inner_init(const struct nft_ctx *ctx,
        struct nft_meta *priv = nft_expr_priv(expr);
        unsigned int len;

+       if (!tb[NFTA_META_KEY] || !tb[NFTA_META_DREG])
+               return -EINVAL;
        priv->key = ntohl(nla_get_be32(tb[NFTA_META_KEY]));
        switch (priv->key) {
        case NFT_META_PROTOCOL:
diff --git a/net/netfilter/nft_payload.c b/net/netfilter/nft_payload.c
index 0c43d748e..4c6f15ad0 100644
--- a/net/netfilter/nft_payload.c
+++ b/net/netfilter/nft_payload.c
@@ -650,6 +650,9 @@ static int nft_payload_inner_init(const struct nft_ctx *ctx,
        struct nft_payload *priv = nft_expr_priv(expr);
        u32 base;

+       if (!tb[NFTA_PAYLOAD_BASE] || !tb[NFTA_PAYLOAD_OFFSET] ||
+           !tb[NFTA_PAYLOAD_LEN] || !tb[NFTA_PAYLOAD_DREG])
+               return -EINVAL;
        base   = ntohl(nla_get_be32(tb[NFTA_PAYLOAD_BASE]));
        switch (base) {
        case NFT_PAYLOAD_TUN_HEADER:
--
2.34.1