2023-07-27 18:04:26

by SeongJae Park

Subject: [PATCH 4.19] net/sched: cls_fw: Fix improper refcount update leads to use-after-free

From: M A Ramdhan <[email protected]>

[ 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.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Reported-by: M A Ramdhan <[email protected]>
Signed-off-by: M A Ramdhan <[email protected]>
Acked-by: Jamal Hadi Salim <[email protected]>
Reviewed-by: Pedro Tammela <[email protected]>
Message-ID: <[email protected]>
Signed-off-by: Jakub Kicinski <[email protected]>
Signed-off-by: SeongJae Park <[email protected]>
---
net/sched/cls_fw.c | 10 +++++-----
1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/net/sched/cls_fw.c b/net/sched/cls_fw.c
index cb2c62605fc76..5284a473c697f 100644
--- a/net/sched/cls_fw.c
+++ b/net/sched/cls_fw.c
@@ -221,11 +221,6 @@ 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);
- }
-
#ifdef CONFIG_NET_CLS_IND
if (tb[TCA_FW_INDEV]) {
int ret;
@@ -244,6 +239,11 @@ 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;
}

--
2.40.1

2023-08-01 09:26:20

by Greg Kroah-Hartman

Subject: Re: [PATCH 4.19] net/sched: cls_fw: Fix improper refcount update leads to use-after-free

On Thu, Jul 27, 2023 at 05:46:28PM +0000, SeongJae Park wrote:
> From: M A Ramdhan <[email protected]>
>
> [ 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.
>
> Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
> Reported-by: M A Ramdhan <[email protected]>
> Signed-off-by: M A Ramdhan <[email protected]>
> Acked-by: Jamal Hadi Salim <[email protected]>
> Reviewed-by: Pedro Tammela <[email protected]>
> Message-ID: <[email protected]>
> Signed-off-by: Jakub Kicinski <[email protected]>
> Signed-off-by: SeongJae Park <[email protected]>
> ---
> net/sched/cls_fw.c | 10 +++++-----

Both now queued up, thanks.

greg k-h