From: Jamal Hadi Salim <jhs@mojatatu.com>
To: Al Viro <viro@ZenIV.linux.org.uk>, netdev@vger.kernel.org
Cc: Cong Wang <xiyou.wangcong@gmail.com>,
Jiri Pirko <jiri@resnulli.us>,
stable@vger.kernel.org
Subject: Re: [PATCH net 01/13] net: sched: cls_u32: fix hnode refcounting
Date: Sun, 9 Sep 2018 07:37:00 -0400 [thread overview]
Message-ID: <129b1730-11ed-9b14-d507-18b9cc21f146@mojatatu.com> (raw)
In-Reply-To: <20180909013132.3222-2-viro@ZenIV.linux.org.uk>
On 2018-09-08 9:31 p.m., Al Viro wrote:
> From: Al Viro <viro@zeniv.linux.org.uk>
>
> cls_u32.c misuses refcounts for struct tc_u_hnode - it counts references via
> ->hlist and via ->tp_root together. u32_destroy() drops the former and, in
> case when there had been links, leaves the sucker on the list. As the result,
> there's nothing to protect it from getting freed once links are dropped.
> That also makes the "is it busy" check incapable of catching the root hnode -
> it *is* busy (there's a reference from tp), but we don't see it as something
> separate. "Is it our root?" check partially covers that, but the problem
> exists for others' roots as well.
>
> AFAICS, the minimal fix preserving the existing behaviour (where it doesn't
> include oopsen, that is) would be this:
> * count tp->root and tp_c->hlist as separate references. I.e.
> have u32_init() set refcount to 2, not 1.
> * in u32_destroy() we always drop the former; in u32_destroy_hnode() -
> the latter.
>
> That way we have *all* references contributing to refcount. List
> removal happens in u32_destroy_hnode() (called only when ->refcnt is 1)
> an in u32_destroy() in case of tc_u_common going away, along with everything
> reachable from it. IOW, that way we know that u32_destroy_key() won't
> free something still on the list (or pointed to by someone's ->root).
>
> Cc: stable@vger.kernel.org
> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
per Cong's earlier remark - the reproducer going in the changelog
would be nice to show i.e this you posted earlier, otherwise:
Tested-by: Jamal Hadi Salim <jhs@mojatatu.com>
Acked-by: Jamal Hadi Salim <jhs@mojatatu.com>
Reminder:
WARNING: multiple messages have this Message-ID (diff)
From: Jamal Hadi Salim <jhs@mojatatu.com>
To: Al Viro <viro@ZenIV.linux.org.uk>, netdev@vger.kernel.org
Cc: Cong Wang <xiyou.wangcong@gmail.com>,
Jiri Pirko <jiri@resnulli.us>,
stable@vger.kernel.org
Subject: Re: [PATCH net 01/13] net: sched: cls_u32: fix hnode refcounting
Date: Sun, 9 Sep 2018 07:37:00 -0400 [thread overview]
Message-ID: <129b1730-11ed-9b14-d507-18b9cc21f146@mojatatu.com> (raw)
In-Reply-To: <20180909013132.3222-2-viro@ZenIV.linux.org.uk>
On 2018-09-08 9:31 p.m., Al Viro wrote:
> From: Al Viro <viro@zeniv.linux.org.uk>
>
> cls_u32.c misuses refcounts for struct tc_u_hnode - it counts references via
> ->hlist and via ->tp_root together. u32_destroy() drops the former and, in
> case when there had been links, leaves the sucker on the list. As the result,
> there's nothing to protect it from getting freed once links are dropped.
> That also makes the "is it busy" check incapable of catching the root hnode -
> it *is* busy (there's a reference from tp), but we don't see it as something
> separate. "Is it our root?" check partially covers that, but the problem
> exists for others' roots as well.
>
> AFAICS, the minimal fix preserving the existing behaviour (where it doesn't
> include oopsen, that is) would be this:
> * count tp->root and tp_c->hlist as separate references. I.e.
> have u32_init() set refcount to 2, not 1.
> * in u32_destroy() we always drop the former; in u32_destroy_hnode() -
> the latter.
>
> That way we have *all* references contributing to refcount. List
> removal happens in u32_destroy_hnode() (called only when ->refcnt is 1)
> an in u32_destroy() in case of tc_u_common going away, along with everything
> reachable from it. IOW, that way we know that u32_destroy_key() won't
> free something still on the list (or pointed to by someone's ->root).
>
> Cc: stable@vger.kernel.org
> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
per Cong's earlier remark - the reproducer going in the changelog
would be nice to show i.e this you posted earlier, otherwise:
Tested-by: Jamal Hadi Salim <jhs@mojatatu.com>
Acked-by: Jamal Hadi Salim <jhs@mojatatu.com>
Reminder:
--
tc qdisc add dev eth0 ingress
tc filter add dev eth0 parent ffff: protocol ip prio 100 handle 1: u32
divisor 1
tc filter add dev eth0 parent ffff: protocol ip prio 200 handle 2: u32
divisor 1
tc filter add dev eth0 parent ffff: protocol ip prio 100 handle 1:0:11
u32 ht 1: link 801: offset at 0 mask 0f00 shift 6 plus 0 eat match ip
protocol 6 ff
tc filter delete dev eth0 parent ffff: protocol ip prio 200
tc filter change dev eth0 parent ffff: protocol ip prio 100 handle
1:0:11 u32 ht 1: link 0: offset at 0 mask 0f00 shift 6 plus 0 eat match
ip protocol 6 ff
tc filter delete dev eth0 parent ffff: protocol ip prio 100
---
cheers,
jamal
next prev parent reply other threads:[~2018-09-09 11:37 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-09 1:31 [PATCH net 00/13] cls_u32 cleanups and fixes Al Viro
2018-09-09 1:31 ` [PATCH net 01/13] net: sched: cls_u32: fix hnode refcounting Al Viro
2018-09-09 11:37 ` Jamal Hadi Salim [this message]
2018-09-09 11:37 ` Jamal Hadi Salim
2018-09-09 1:31 ` [PATCH net 02/13] net: sched: cls_u32: mark root hnode explicitly Al Viro
2018-09-09 11:39 ` Jamal Hadi Salim
2018-09-09 1:31 ` [PATCH net 03/13] net: sched: cls_u32: disallow linking to root hnode Al Viro
2018-09-09 11:39 ` Jamal Hadi Salim
2018-09-09 1:31 ` [PATCH net 04/13] net: sched: cls_u32: make sure that divisor is a power of 2 Al Viro
2018-09-09 11:41 ` Jamal Hadi Salim
2018-09-09 1:31 ` [PATCH net 05/13] net: sched: cls_u32: get rid of unused argument of u32_destroy_key() Al Viro
2018-09-09 11:41 ` Jamal Hadi Salim
2018-09-09 1:31 ` [PATCH net 06/13] net: sched: cls_u32: get rid of tc_u_knode ->tp Al Viro
2018-09-09 11:43 ` Jamal Hadi Salim
2018-09-09 1:31 ` [PATCH net 07/13] net: sched: cls_u32: get rid of tc_u_common ->rcu Al Viro
2018-09-09 11:45 ` Jamal Hadi Salim
2018-09-09 1:31 ` [PATCH net 08/13] net: sched: cls_u32: clean tc_u_common hashtable Al Viro
2018-09-09 11:47 ` Jamal Hadi Salim
2018-09-09 1:31 ` [PATCH net 09/13] net: sched: cls_u32: pass tc_u_common to u32_set_parms() instead of tc_u_hnode Al Viro
2018-09-09 11:52 ` Jamal Hadi Salim
2018-09-09 1:31 ` [PATCH net 10/13] net: sched: cls_u32: the tp_c argument of u32_set_parms() is always tp->data Al Viro
2018-09-09 12:48 ` Jamal Hadi Salim
2018-09-09 1:31 ` [PATCH net 11/13] net: sched: cls_u32: get rid of hnode ->tp_c and tp_c argument of u32_set_parms() Al Viro
2018-09-09 12:49 ` Jamal Hadi Salim
2018-09-09 1:31 ` [PATCH net 12/13] net: sched: cls_u32: keep track of knodes count in tc_u_common Al Viro
2018-09-09 12:50 ` Jamal Hadi Salim
2018-09-09 1:31 ` [PATCH net 13/13] net: sched: cls_u32: simplify the hell out u32_delete() emptiness check Al Viro
2018-09-09 12:51 ` Jamal Hadi Salim
2018-09-09 12:58 ` [PATCH net 00/13] cls_u32 cleanups and fixes Jamal Hadi Salim
2018-09-09 14:15 ` Al Viro
2018-09-09 15:48 ` Al Viro
2018-09-10 12:25 ` Offloaded u32 classifier tables WAS (Re: " Jamal Hadi Salim
2018-09-10 12:31 ` Jamal Hadi Salim
2018-09-10 11:30 ` Jamal Hadi Salim
2018-09-12 6:15 ` David Miller
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