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Subject[PATCH 1/1] net/sched: cls_u32: Fix reference counter leak leading to overflow
Date
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'.

Cc: stable@kernel.org # v4.14+
Signed-off-by: Lee Jones <lee@kernel.org>
---
net/sched/cls_u32.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/net/sched/cls_u32.c b/net/sched/cls_u32.c
index 4e2e269f121f8..fad61ca5e90bf 100644
--- a/net/sched/cls_u32.c
+++ b/net/sched/cls_u32.c
@@ -762,8 +762,11 @@ static int u32_set_parms(struct net *net, struct tcf_proto *tp,
if (tb[TCA_U32_INDEV]) {
int ret;
ret = tcf_change_indev(net, tb[TCA_U32_INDEV], extack);
- if (ret < 0)
+ if (ret < 0) {
+ if (tb[TCA_U32_LINK])
+ n->ht_down->refcnt--;
return -EINVAL;
+ }
n->ifindex = ret;
}
return 0;
--
2.41.0.rc0.172.g3f132b7071-goog
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