* Attempt to auto-load em_cmp.ko results in negative module refcnt
@ 2015-02-16 10:59 Ignacy Gawedzki
2015-02-16 15:03 ` Ignacy Gawedzki
0 siblings, 1 reply; 9+ messages in thread
From: Ignacy Gawedzki @ 2015-02-16 10:59 UTC (permalink / raw)
To: netdev
Hi,
This simple test case
tc qdisc add dev eth0 root handle 1: htb
tc class add dev eth0 root classid 1: htb rate 1Gbit
tc class add dev eth0 parent 1: classid 1:1 htb rate 1Gbit
tc filter add dev eth0 parent 1: basic match 'cmp(u8 at 0 eq 0)' classid 1:1
fails with the following
RTNETLINK answers: No such file or directory
We have an error talking to the kernel
if em_cmp.ko is not loaded beforehand.
After that, lsmod shows that em_cmp.ko is loaded indeed, but its usage count
is -1 and an attempd to unload the module results in a "BUG at
kernel/module.c:752".
This has been broken pretty recently, I'm currently attempting a git bisect on
this.
--
Ignacy Gawędzki
R&D Engineer
Green Communications
^ permalink raw reply [flat|nested] 9+ messages in thread
* Re: Attempt to auto-load em_cmp.ko results in negative module refcnt
2015-02-16 10:59 Attempt to auto-load em_cmp.ko results in negative module refcnt Ignacy Gawedzki
@ 2015-02-16 15:03 ` Ignacy Gawedzki
2015-02-16 18:13 ` [PATCH net] ematch: Fix auto-loading of ematch modules Ignacy Gawędzki
0 siblings, 1 reply; 9+ messages in thread
From: Ignacy Gawedzki @ 2015-02-16 15:03 UTC (permalink / raw)
To: netdev
On Mon, Feb 16, 2015 at 11:59:12AM +0100, thus spake Ignacy Gawedzki:
> This has been broken pretty recently, I'm currently attempting a git bisect on
> this.
Okay, the bisect tells this appeared with
e513cc1c07e2ab93a4514eec9833e031df3e30bb, FWIW.
--
Ignacy Gawędzki
R&D Engineer
Green Communications
^ permalink raw reply [flat|nested] 9+ messages in thread
* [PATCH net] ematch: Fix auto-loading of ematch modules.
2015-02-16 15:03 ` Ignacy Gawedzki
@ 2015-02-16 18:13 ` Ignacy Gawędzki
2015-02-16 18:36 ` Cong Wang
0 siblings, 1 reply; 9+ messages in thread
From: Ignacy Gawędzki @ 2015-02-16 18:13 UTC (permalink / raw)
To: netdev
In tcf_em_validate(), when calling tcf_em_lookup(), don't put the resulting
pointer directly into em->ops, if the function is to possibly return -EAGAIN
after module auto-loading. Otherwise, module_put() will be called by
tcf_em_tree_destroy() on em->ops->owner, while it has already been called by
tcf_em_validate() before return.
Signed-off-by: Ignacy Gawędzki <ignacy.gawedzki@green-communications.fr>
---
net/sched/ematch.c | 13 ++++++++-----
1 file changed, 8 insertions(+), 5 deletions(-)
diff --git a/net/sched/ematch.c b/net/sched/ematch.c
index 6742200..39fbe2f 100644
--- a/net/sched/ematch.c
+++ b/net/sched/ematch.c
@@ -176,6 +176,7 @@ static int tcf_em_validate(struct tcf_proto *tp,
{
int err = -EINVAL;
struct tcf_ematch_hdr *em_hdr = nla_data(nla);
+ struct tcf_ematch_ops *em_ops;
int data_len = nla_len(nla) - sizeof(*em_hdr);
void *data = (void *) em_hdr + sizeof(*em_hdr);
struct net *net = dev_net(qdisc_dev(tp->q));
@@ -213,27 +214,29 @@ static int tcf_em_validate(struct tcf_proto *tp,
* here. Be aware, the destroy function assumes that the
* module is held if the ops field is non zero.
*/
- em->ops = tcf_em_lookup(em_hdr->kind);
+ em_ops = tcf_em_lookup(em_hdr->kind);
- if (em->ops == NULL) {
+ if (em_ops == NULL) {
err = -ENOENT;
#ifdef CONFIG_MODULES
__rtnl_unlock();
request_module("ematch-kind-%u", em_hdr->kind);
rtnl_lock();
- em->ops = tcf_em_lookup(em_hdr->kind);
- if (em->ops) {
+ em_ops = tcf_em_lookup(em_hdr->kind);
+ if (em_ops) {
/* We dropped the RTNL mutex in order to
* perform the module load. Tell the caller
* to replay the request.
*/
- module_put(em->ops->owner);
+ module_put(em_ops->owner);
err = -EAGAIN;
}
#endif
goto errout;
}
+ em->ops = em_ops;
+
/* ematch module provides expected length of data, so we
* can do a basic sanity check.
*/
--
2.1.0
^ permalink raw reply related [flat|nested] 9+ messages in thread
* Re: [PATCH net] ematch: Fix auto-loading of ematch modules.
2015-02-16 18:13 ` [PATCH net] ematch: Fix auto-loading of ematch modules Ignacy Gawędzki
@ 2015-02-16 18:36 ` Cong Wang
2015-02-16 18:50 ` Ignacy Gawędzki
0 siblings, 1 reply; 9+ messages in thread
From: Cong Wang @ 2015-02-16 18:36 UTC (permalink / raw)
To: Ignacy Gawędzki, netdev
On Mon, Feb 16, 2015 at 10:13 AM, Ignacy Gawędzki
<ignacy.gawedzki@green-communications.fr> wrote:
> In tcf_em_validate(), when calling tcf_em_lookup(), don't put the resulting
> pointer directly into em->ops, if the function is to possibly return -EAGAIN
> after module auto-loading. Otherwise, module_put() will be called by
> tcf_em_tree_destroy() on em->ops->owner, while it has already been called by
> tcf_em_validate() before return.
>
Or simply reset em->ops to NULL after module_put()?
^ permalink raw reply [flat|nested] 9+ messages in thread
* Re: [PATCH net] ematch: Fix auto-loading of ematch modules.
2015-02-16 18:36 ` Cong Wang
@ 2015-02-16 18:50 ` Ignacy Gawędzki
2015-02-17 18:00 ` Cong Wang
0 siblings, 1 reply; 9+ messages in thread
From: Ignacy Gawędzki @ 2015-02-16 18:50 UTC (permalink / raw)
To: Cong Wang; +Cc: netdev
On Mon, Feb 16, 2015 at 10:36:06AM -0800, thus spake Cong Wang:
> On Mon, Feb 16, 2015 at 10:13 AM, Ignacy Gawędzki
> <ignacy.gawedzki@green-communications.fr> wrote:
> > In tcf_em_validate(), when calling tcf_em_lookup(), don't put the resulting
> > pointer directly into em->ops, if the function is to possibly return -EAGAIN
> > after module auto-loading. Otherwise, module_put() will be called by
> > tcf_em_tree_destroy() on em->ops->owner, while it has already been called by
> > tcf_em_validate() before return.
> >
>
> Or simply reset em->ops to NULL after module_put()?
Yeah, why not. I just got my inspiration from what's done in cls_api.c and
act_api.c. What do you think, should the same simplification be applied to
cls_api.c?
--
Ignacy Gawędzki
R&D Engineer
Green Communications
^ permalink raw reply [flat|nested] 9+ messages in thread
* Re: [PATCH net] ematch: Fix auto-loading of ematch modules.
2015-02-16 18:50 ` Ignacy Gawędzki
@ 2015-02-17 18:00 ` Cong Wang
2015-02-17 19:15 ` [PATCH net v2] " Ignacy Gawędzki
0 siblings, 1 reply; 9+ messages in thread
From: Cong Wang @ 2015-02-17 18:00 UTC (permalink / raw)
To: Ignacy Gawędzki, Cong Wang, netdev
On Mon, Feb 16, 2015 at 10:50 AM, Ignacy Gawędzki
<ignacy.gawedzki@green-communications.fr> wrote:
> On Mon, Feb 16, 2015 at 10:36:06AM -0800, thus spake Cong Wang:
>> On Mon, Feb 16, 2015 at 10:13 AM, Ignacy Gawędzki
>> <ignacy.gawedzki@green-communications.fr> wrote:
>> > In tcf_em_validate(), when calling tcf_em_lookup(), don't put the resulting
>> > pointer directly into em->ops, if the function is to possibly return -EAGAIN
>> > after module auto-loading. Otherwise, module_put() will be called by
>> > tcf_em_tree_destroy() on em->ops->owner, while it has already been called by
>> > tcf_em_validate() before return.
>> >
>>
>> Or simply reset em->ops to NULL after module_put()?
>
> Yeah, why not. I just got my inspiration from what's done in cls_api.c and
> act_api.c. What do you think, should the same simplification be applied to
> cls_api.c?
>
I prefer the smaller change, we don't have to align with cls_api.c.
Yeah, you can always clean it up for net-next.
Thanks.
^ permalink raw reply [flat|nested] 9+ messages in thread
* [PATCH net v2] ematch: Fix auto-loading of ematch modules.
2015-02-17 18:00 ` Cong Wang
@ 2015-02-17 19:15 ` Ignacy Gawędzki
2015-02-18 5:17 ` Cong Wang
2015-02-20 20:31 ` David Miller
0 siblings, 2 replies; 9+ messages in thread
From: Ignacy Gawędzki @ 2015-02-17 19:15 UTC (permalink / raw)
To: netdev
In tcf_em_validate(), after calling request_module() to load the
kind-specific module, set em->ops to NULL before returning -EAGAIN, so
that module_put() is not called again by tcf_em_tree_destroy().
Signed-off-by: Ignacy Gawędzki <ignacy.gawedzki@green-communications.fr>
---
net/sched/ematch.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/net/sched/ematch.c b/net/sched/ematch.c
index 6742200..fbb7ebf 100644
--- a/net/sched/ematch.c
+++ b/net/sched/ematch.c
@@ -228,6 +228,7 @@ static int tcf_em_validate(struct tcf_proto *tp,
* to replay the request.
*/
module_put(em->ops->owner);
+ em->ops = NULL;
err = -EAGAIN;
}
#endif
--
2.1.0
^ permalink raw reply related [flat|nested] 9+ messages in thread
* Re: [PATCH net v2] ematch: Fix auto-loading of ematch modules.
2015-02-17 19:15 ` [PATCH net v2] " Ignacy Gawędzki
@ 2015-02-18 5:17 ` Cong Wang
2015-02-20 20:31 ` David Miller
1 sibling, 0 replies; 9+ messages in thread
From: Cong Wang @ 2015-02-18 5:17 UTC (permalink / raw)
To: Ignacy Gawędzki, netdev
On Tue, Feb 17, 2015 at 11:15 AM, Ignacy Gawędzki
<ignacy.gawedzki@green-communications.fr> wrote:
> In tcf_em_validate(), after calling request_module() to load the
> kind-specific module, set em->ops to NULL before returning -EAGAIN, so
> that module_put() is not called again by tcf_em_tree_destroy().
>
> Signed-off-by: Ignacy Gawędzki <ignacy.gawedzki@green-communications.fr>
Acked-by: Cong Wang <cwang@twopensource.com>
^ permalink raw reply [flat|nested] 9+ messages in thread
* Re: [PATCH net v2] ematch: Fix auto-loading of ematch modules.
2015-02-17 19:15 ` [PATCH net v2] " Ignacy Gawędzki
2015-02-18 5:17 ` Cong Wang
@ 2015-02-20 20:31 ` David Miller
1 sibling, 0 replies; 9+ messages in thread
From: David Miller @ 2015-02-20 20:31 UTC (permalink / raw)
To: ignacy.gawedzki; +Cc: netdev
From: Ignacy Gawędzki <ignacy.gawedzki@green-communications.fr>
Date: Tue, 17 Feb 2015 20:15:20 +0100
> In tcf_em_validate(), after calling request_module() to load the
> kind-specific module, set em->ops to NULL before returning -EAGAIN, so
> that module_put() is not called again by tcf_em_tree_destroy().
>
> Signed-off-by: Ignacy Gawędzki <ignacy.gawedzki@green-communications.fr>
Applied and queued up for -stable, thanks.
^ permalink raw reply [flat|nested] 9+ messages in thread
end of thread, other threads:[~2015-02-20 20:31 UTC | newest]
Thread overview: 9+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2015-02-16 10:59 Attempt to auto-load em_cmp.ko results in negative module refcnt Ignacy Gawedzki
2015-02-16 15:03 ` Ignacy Gawedzki
2015-02-16 18:13 ` [PATCH net] ematch: Fix auto-loading of ematch modules Ignacy Gawędzki
2015-02-16 18:36 ` Cong Wang
2015-02-16 18:50 ` Ignacy Gawędzki
2015-02-17 18:00 ` Cong Wang
2015-02-17 19:15 ` [PATCH net v2] " Ignacy Gawędzki
2015-02-18 5:17 ` Cong Wang
2015-02-20 20:31 ` David Miller
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