Commit f38754f7 authored Jul 05, 2023 by M A Ramdhan Committed by Lee Jones Aug 15, 2023

UPSTREAM: net/sched: cls_fw: Fix improper refcount update leads to use-after-free



[ Upstream commit 0323bce598eea038714f941ce2b22541c46d488f ]

In the event of a failure in tcf_change_indev(), fw_set_parms() will
immediately return an error after incrementing or decrementing
reference counter in tcf_bind_filter().  If attacker can control
reference counter to zero and make reference freed, leading to
use after free.

In order to prevent this, move the point of possible failure above the
point where the TC_FW_CLASSID is handled.

Bug: 292252062
Bug: 290783303
Fixes: 1da177e4 ("Linux-2.6.12-rc2")
Reported-by: M A Ramdhan <ramdhan@starlabs.sg>
Signed-off-by: M A Ramdhan <ramdhan@starlabs.sg>
Acked-by: Jamal Hadi Salim <jhs@mojatatu.com>
Reviewed-by: Pedro Tammela <pctammela@mojatatu.com>
Message-ID: <20230705161530.52003-1-ramdhan@starlabs.sg>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
(cherry picked from commit c91fb29bb07ee4dd40aabd1e41f19c0f92ac3199)
Signed-off-by: Lee Jones <joneslee@google.com>
Change-Id: I9bf6f540b4eb23ea5641fb3efe6f3e621d7b6151

parent 07452ef6

net/sched/cls_fw.c

+5 −5

Original line number	Diff line number	Diff line
		@@ -210,11 +210,6 @@ static int fw_set_parms(struct net net, struct tcf_proto tp,
		if (err < 0)
		return err;

		if (tb[TCA_FW_CLASSID]) {
		f->res.classid = nla_get_u32(tb[TCA_FW_CLASSID]);
		tcf_bind_filter(tp, &f->res, base);
		}

		if (tb[TCA_FW_INDEV]) {
		int ret;
		ret = tcf_change_indev(net, tb[TCA_FW_INDEV], extack);
		@@ -231,6 +226,11 @@ static int fw_set_parms(struct net net, struct tcf_proto tp,
		} else if (head->mask != 0xFFFFFFFF)
		return err;

		if (tb[TCA_FW_CLASSID]) {
		f->res.classid = nla_get_u32(tb[TCA_FW_CLASSID]);
		tcf_bind_filter(tp, &f->res, base);
		}

		return 0;
		}