On Thu, 27 Jul 2023 19:15:54 +0000 Rishabh Bhatnagar <risbhat@xxxxxxxxxx> wrote:
> From: Lee Jones <lee@xxxxxxxxxx>
>
> Upstream commit 04c55383fa5689357bcdd2c8036725a55ed632bc.
>
> In the event of a failure in tcf_change_indev(), u32_set_parms() will
> immediately return without decrementing the recently incremented
> reference counter. If this happens enough times, the counter will
> rollover and the reference freed, leading to a double free which can be
> used to do 'bad things'.
>
> In order to prevent this, move the point of possible failure above the
> point where the reference counter is incremented. Also save any
> meaningful return values to be applied to the return data at the
> appropriate point in time.
>
> This issue was caught with KASAN.
>
> Fixes: 705c7091262d ("net: sched: cls_u32: no need to call tcf_exts_change for newly allocated struct")
> Suggested-by: Eric Dumazet <edumazet@xxxxxxxxxx>
> Signed-off-by: Lee Jones <lee@xxxxxxxxxx>
> Reviewed-by: Eric Dumazet <edumazet@xxxxxxxxxx>
> Acked-by: Jamal Hadi Salim <jhs@xxxxxxxxxxxx>
> Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
> Signed-off-by: Rishabh Bhatnagar <risbhat@xxxxxxxxxx>
Acked-by: SeongJae Park <sj@xxxxxxxxxx>
> ---
> net/sched/cls_u32.c | 21 ++++++++++++++-------
> 1 file changed, 14 insertions(+), 7 deletions(-)
>
> diff --git a/net/sched/cls_u32.c b/net/sched/cls_u32.c
> index fdbdcba44917..a4e01220a53a 100644
> --- a/net/sched/cls_u32.c
> +++ b/net/sched/cls_u32.c
> @@ -774,11 +774,22 @@ static int u32_set_parms(struct net *net, struct tcf_proto *tp,
> struct nlattr *est, bool ovr)
> {
> int err;
> +#ifdef CONFIG_NET_CLS_IND
> + int ifindex = -1;
> +#endif
>
> err = tcf_exts_validate(net, tp, tb, est, &n->exts, ovr);
> if (err < 0)
> return err;
>
> +#ifdef CONFIG_NET_CLS_IND
> + if (tb[TCA_U32_INDEV]) {
> + ifindex = tcf_change_indev(net, tb[TCA_U32_INDEV]);
> + if (ifindex < 0)
> + return -EINVAL;
> + }
> +#endif
> +
> if (tb[TCA_U32_LINK]) {
> u32 handle = nla_get_u32(tb[TCA_U32_LINK]);
> struct tc_u_hnode *ht_down = NULL, *ht_old;
> @@ -806,14 +817,10 @@ static int u32_set_parms(struct net *net, struct tcf_proto *tp,
> }
>
> #ifdef CONFIG_NET_CLS_IND
> - if (tb[TCA_U32_INDEV]) {
> - int ret;
> - ret = tcf_change_indev(net, tb[TCA_U32_INDEV]);
> - if (ret < 0)
> - return -EINVAL;
> - n->ifindex = ret;
> - }
> + if (ifindex >= 0)
> + n->ifindex = ifindex;
> #endif
> +
> return 0;
Very trivial nit: Someone might think the above new line is better not to be
added? I don't really care, though.
> }
>
> --
> 2.40.1
>
Thanks,
SJ
