* kernel panic in pppoe_release
@ 2015-08-28 19:01 Murat Sezgin
0 siblings, 0 replies; only message in thread
From: Murat Sezgin @ 2015-08-28 19:01 UTC (permalink / raw)
To: linux-ppp
Hi all,
We are using 3.4.103 kernel on our openwrt router platform. In the event of
interface down, we get kernel panic in the pppoe_release() function, because
the po->pppoe_dev comes to this function as NULL and dev_put() is called
without doing any NULL check.
I see that openwrt community has done an improvement for this issue with the
following commits in 3.18 and 4.0 kernels.
https://dev.openwrt.org/changeset/45653
I back ported these commits to our kernel and they increased the issue
occurrence frequency, but they didn't fix the issue completely. I ended up
that we need a NULL check in the pppoe_release() function as well. It seems
there is still a race between the pppoe_release() and the pppoe_flush_dev().
So, added the below change, but I would like to see whether this may have
side effects or not.
Can somebody please make comments on this?
@@ -589,7 +606,7 @@ static int pppoe_release(struct socket *sock)
po = pppox_sk(sk);
- if (sk->sk_state & (PPPOX_CONNECTED | PPPOX_BOUND | PPPOX_ZOMBIE)) {
+ if (po->pppoe_dev && sk->sk_state & (PPPOX_CONNECTED | PPPOX_BOUND |
PPPOX_ZOMBIE)) {
dev_put(po->pppoe_dev);
po->pppoe_dev = NULL;
}
Regards,
Murat
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