[PATCH 6.4 698/800] net/sched: act_pedit: Add size check for TCA_PEDIT_PARMS_EX

Greg Kroah-Hartman
2023-07-16T20:25:28Z

From: Lin Ma <linma@zju.edu.cn>

[ Upstream commit 30c45b5361d39b4b793780ffac5538090b9e2eb1 ]

The attribute TCA_PEDIT_PARMS_EX is not be included in pedit_policy and
one malicious user could fake a TCA_PEDIT_PARMS_EX whose length is
smaller than the intended sizeof(struct tc_pedit). Hence, the
dereference in tcf_pedit_init() could access dirty heap data.

static int tcf_pedit_init(...)
{
// ...
pattr = tb[TCA_PEDIT_PARMS]; // TCA_PEDIT_PARMS is included
if (!pattr)
pattr = tb[TCA_PEDIT_PARMS_EX]; // but this is not

// ...
parm = nla_data(pattr);

index = parm->index; // parm is able to be smaller than 4 bytes
// and this dereference gets dirty skb_buff
// data created in netlink_sendmsg
}

This commit adds TCA_PEDIT_PARMS_EX length in pedit_policy which avoid
the above case, just like the TCA_PEDIT_PARMS.

Fixes: 71d0ed7079df ("net/act_pedit: Support using offset relative to the conventional network headers")
Signed-off-by: Lin Ma <linma@zju.edu.cn>
Reviewed-by: Pedro Tammela <pctammela@mojatatu.com>
Link: https://lore.kernel.org/r/20230703110842.590282-1-linma@zju.edu.cn
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/sched/act_pedit.c | 1 +
1 file changed, 1 insertion(+)

diff --git a/net/sched/act_pedit.c b/net/sched/act_pedit.c
index c819b812a899c..399d4643a940e 100644
--- a/net/sched/act_pedit.c
+++ b/net/sched/act_pedit.c
@@ -29,6 +29,7 @@ static struct tc_action_ops act_pedit_ops;

static const struct nla_policy pedit_policy[TCA_PEDIT_MAX + 1] = {
[TCA_PEDIT_PARMS] = { .len = sizeof(struct tc_pedit) },
+ [TCA_PEDIT_PARMS_EX] = { .len = sizeof(struct tc_pedit) },
[TCA_PEDIT_KEYS_EX] = { .type = NLA_NESTED },
};

--
2.39.2