From: Lee Jones lee@kernel.org
commit 04c55383fa5689357bcdd2c8036725a55ed632bc upstream.
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@google.com Signed-off-by: Lee Jones lee@kernel.org Reviewed-by: Eric Dumazet edumazet@google.com Acked-by: Jamal Hadi Salim jhs@mojatatu.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Rishabh Bhatnagar risbhat@amazon.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/sched/cls_u32.c | 21 ++++++++++++++------- 1 file changed, 14 insertions(+), 7 deletions(-)
--- 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 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 }
#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; }