netfilter: nf_tables: reject QUEUE/DROP verdict parameters

This reverts commit e0abdadcc6e1.

core.c:nf_hook_slow assumes that the upper 16 bits of NF_DROP
verdicts contain a valid errno, i.e. -EPERM, -EHOSTUNREACH or similar,
or 0.

Due to the reverted commit, its possible to provide a positive
value, e.g. NF_ACCEPT (1), which results in use-after-free.

Its not clear to me why this commit was made.

NF_QUEUE is not used by nftables; "queue" rules in nftables
will result in use of "nft_queue" expression.

If we later need to allow specifiying errno values from userspace
(do not know why), this has to call NF_DROP_GETERR and check that
"err <= 0" holds true.

Fixes: e0abdadcc6e1 ("netfilter: nf_tables: accept QUEUE/DROP verdict parameters")
Cc: stable@vger.kernel.org
Reported-by: Notselwyn <notselwyn@pwning.tech>
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
index 02f45424644b4d2e4172d5b5cd9255fcb5a893b8..c537104411e7d1b1c1b449b55c7a3c43fb7e2ac3 100644 (file)
--- a/net/netfilter/nf_tables_api.c
+++ b/net/netfilter/nf_tables_api.c
@@ -10992,16 +10992,10 @@ static int nft_verdict_init(const struct nft_ctx *ctx, struct nft_data *data,
        data->verdict.code = ntohl(nla_get_be32(tb[NFTA_VERDICT_CODE]));
 
        switch (data->verdict.code) {
-       default:
-               switch (data->verdict.code & NF_VERDICT_MASK) {
-               case NF_ACCEPT:
-               case NF_DROP:
-               case NF_QUEUE:
-                       break;
-               default:
-                       return -EINVAL;
-               }
-               fallthrough;
+       case NF_ACCEPT:
+       case NF_DROP:
+       case NF_QUEUE:
+               break;
        case NFT_CONTINUE:
        case NFT_BREAK:
        case NFT_RETURN:
@@ -11036,6 +11030,8 @@ static int nft_verdict_init(const struct nft_ctx *ctx, struct nft_data *data,
 
                data->verdict.chain = chain;
                break;
+       default:
+               return -EINVAL;
        }
 
        desc->len = sizeof(data->verdict);