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netfilter: nf_tables: reject QUEUE/DROP verdict parameters 

This reverts commit e0abdadcc6.

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: e0abdadcc6 ("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>
This commit is contained in:
Florian Westphal 2024-01-20 22:50:04 +01:00 committed by Pablo Neira Ayuso
parent b462579b2b
commit f342de4e2f
1 changed files with 6 additions and 10 deletions
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16
net/netfilter/nf_tables_api.c
View File

@ -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);