Commit 4e66422f authored Jan 20, 2024 by Florian Westphal Committed by Greg Kroah-Hartman Feb 23, 2024

netfilter: nf_tables: reject QUEUE/DROP verdict parameters



commit f342de4e2f33e0e39165d8639387aa6c19dff660 upstream.

This reverts commit e0abdadc.

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: e0abdadc ("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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent bd517df3

net/netfilter/nf_tables_api.c

+6 −10

Original line number	Diff line number	Diff line
		@@ -8058,16 +8058,10 @@ 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;
		}
		/* fall through */
		case NFT_CONTINUE:
		case NFT_BREAK:
		case NFT_RETURN:
		@@ -8087,6 +8081,8 @@ 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);