[PATCH] tc: Fix unitialized kernel memory leak

[PATCH] tc: Fix unitialized kernel memory leak

[Eric Dumazet]

Three bytes of uninitialized kernel memory are currently leaked to user

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
---
diff --git a/net/sched/sch_api.c b/net/sched/sch_api.c
index 24d17ce..fdb694e 100644
--- a/net/sched/sch_api.c
+++ b/net/sched/sch_api.c
@@ -1456,6 +1456,8 @@ static int tc_fill_tclass(struct sk_buff *skb, struct Qdisc *q,
 	nlh = NLMSG_NEW(skb, pid, seq, event, sizeof(*tcm), flags);
 	tcm = NLMSG_DATA(nlh);
 	tcm->tcm_family = AF_UNSPEC;
+	tcm->tcm__pad1 = 0;
+	tcm->tcm__pad2 = 0;
 	tcm->tcm_ifindex = qdisc_dev(q)->ifindex;
 	tcm->tcm_parent = q->handle;
 	tcm->tcm_handle = q->handle;

Re: [PATCH] tc: Fix unitialized kernel memory leak

[Jiri Pirko]

Wed, Sep 02, 2009 at 02:40:09PM CEST, eric.dumazet@gmail.com wrote:
>Three bytes of uninitialized kernel memory are currently leaked to user
>
>Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>

Reviewed-by: Jiri Pirko <jpirko@redhat.com>

>---
>diff --git a/net/sched/sch_api.c b/net/sched/sch_api.c
>index 24d17ce..fdb694e 100644
>--- a/net/sched/sch_api.c
>+++ b/net/sched/sch_api.c
>@@ -1456,6 +1456,8 @@ static int tc_fill_tclass(struct sk_buff *skb, struct Qdisc *q,
> 	nlh = NLMSG_NEW(skb, pid, seq, event, sizeof(*tcm), flags);
> 	tcm = NLMSG_DATA(nlh);
> 	tcm->tcm_family = AF_UNSPEC;
>+	tcm->tcm__pad1 = 0;
>+	tcm->tcm__pad2 = 0;
> 	tcm->tcm_ifindex = qdisc_dev(q)->ifindex;
> 	tcm->tcm_parent = q->handle;
> 	tcm->tcm_handle = q->handle;
>--
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Re: [PATCH] tc: Fix unitialized kernel memory leak

[Stephen Hemminger]

On Wed, 02 Sep 2009 14:40:09 +0200
Eric Dumazet <eric.dumazet@gmail.com> wrote:

> Three bytes of uninitialized kernel memory are currently leaked to user
> 
> Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
> ---
> diff --git a/net/sched/sch_api.c b/net/sched/sch_api.c
> index 24d17ce..fdb694e 100644
> --- a/net/sched/sch_api.c
> +++ b/net/sched/sch_api.c
> @@ -1456,6 +1456,8 @@ static int tc_fill_tclass(struct sk_buff *skb, struct Qdisc *q,
>  	nlh = NLMSG_NEW(skb, pid, seq, event, sizeof(*tcm), flags);
>  	tcm = NLMSG_DATA(nlh);
>  	tcm->tcm_family = AF_UNSPEC;
> +	tcm->tcm__pad1 = 0;
> +	tcm->tcm__pad2 = 0;
>  	tcm->tcm_ifindex = qdisc_dev(q)->ifindex;
>  	tcm->tcm_parent = q->handle;
>  	tcm->tcm_handle = q->handle;

Perhaps __nlmsg_put should just always call memset() for the whole
added chunk. It is not like it is critical path in any way, and
avoid any of this possible class of errors.

Re: [PATCH] tc: Fix unitialized kernel memory leak

[David Miller]

From: Stephen Hemminger <shemminger@vyatta.com>
Date: Wed, 2 Sep 2009 12:05:40 -0700

> On Wed, 02 Sep 2009 14:40:09 +0200
> Eric Dumazet <eric.dumazet@gmail.com> wrote:
> 
>> Three bytes of uninitialized kernel memory are currently leaked to user
>> 
>> Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
>> ---
>> diff --git a/net/sched/sch_api.c b/net/sched/sch_api.c
>> index 24d17ce..fdb694e 100644
>> --- a/net/sched/sch_api.c
>> +++ b/net/sched/sch_api.c
>> @@ -1456,6 +1456,8 @@ static int tc_fill_tclass(struct sk_buff *skb, struct Qdisc *q,
>>  	nlh = NLMSG_NEW(skb, pid, seq, event, sizeof(*tcm), flags);
>>  	tcm = NLMSG_DATA(nlh);
>>  	tcm->tcm_family = AF_UNSPEC;
>> +	tcm->tcm__pad1 = 0;
>> +	tcm->tcm__pad2 = 0;
>>  	tcm->tcm_ifindex = qdisc_dev(q)->ifindex;
>>  	tcm->tcm_parent = q->handle;
>>  	tcm->tcm_handle = q->handle;
> 
> Perhaps __nlmsg_put should just always call memset() for the whole
> added chunk. It is not like it is critical path in any way, and
> avoid any of this possible class of errors.

Doing it in __nlmsg_put would effect a lot of code paths.  I don't
think you can say with certainty that it won't matter, tree wide.

What about things like the netfilter conntrack event monitor?  Doesn't
that emit hundreds of thousands of events per second on a busy
firewall?

Re: [PATCH] tc: Fix unitialized kernel memory leak

[David Miller]

From: Jiri Pirko <jpirko@redhat.com>
Date: Wed, 2 Sep 2009 20:09:36 +0200

> Wed, Sep 02, 2009 at 02:40:09PM CEST, eric.dumazet@gmail.com wrote:
>>Three bytes of uninitialized kernel memory are currently leaked to user
>>
>>Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
> 
> Reviewed-by: Jiri Pirko <jpirko@redhat.com>

I'll apply this to net-2.6, thanks everyone.

Re: [PATCH] tc: Fix unitialized kernel memory leak

[Stephen Hemminger]

On Wed, 02 Sep 2009 22:51:08 -0700 (PDT)
David Miller <davem@davemloft.net> wrote:

> From: Stephen Hemminger <shemminger@vyatta.com>
> Date: Wed, 2 Sep 2009 12:05:40 -0700
> 
> > On Wed, 02 Sep 2009 14:40:09 +0200
> > Eric Dumazet <eric.dumazet@gmail.com> wrote:
> > 
> >> Three bytes of uninitialized kernel memory are currently leaked to user
> >> 
> >> Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
> >> ---
> >> diff --git a/net/sched/sch_api.c b/net/sched/sch_api.c
> >> index 24d17ce..fdb694e 100644
> >> --- a/net/sched/sch_api.c
> >> +++ b/net/sched/sch_api.c
> >> @@ -1456,6 +1456,8 @@ static int tc_fill_tclass(struct sk_buff *skb, struct Qdisc *q,
> >>  	nlh = NLMSG_NEW(skb, pid, seq, event, sizeof(*tcm), flags);
> >>  	tcm = NLMSG_DATA(nlh);
> >>  	tcm->tcm_family = AF_UNSPEC;
> >> +	tcm->tcm__pad1 = 0;
> >> +	tcm->tcm__pad2 = 0;
> >>  	tcm->tcm_ifindex = qdisc_dev(q)->ifindex;
> >>  	tcm->tcm_parent = q->handle;
> >>  	tcm->tcm_handle = q->handle;
> > 
> > Perhaps __nlmsg_put should just always call memset() for the whole
> > added chunk. It is not like it is critical path in any way, and
> > avoid any of this possible class of errors.
> 
> Doing it in __nlmsg_put would effect a lot of code paths.  I don't
> think you can say with certainty that it won't matter, tree wide.
> 
> What about things like the netfilter conntrack event monitor?  Doesn't
> that emit hundreds of thousands of events per second on a busy
> firewall?

I doubt it would make a noticeable performance difference because
the first memset would incur the cache penalty of the write (if any)
and later update of fields would be cached.

-- 

Re: [PATCH] tc: Fix unitialized kernel memory leak

[David Miller]

From: Stephen Hemminger <shemminger@vyatta.com>
Date: Wed, 2 Sep 2009 23:34:10 -0700

> I doubt it would make a noticeable performance difference because
> the first memset would incur the cache penalty of the write (if any)
> and later update of fields would be cached.

Indeed, but it also means your store buffer usage is half as effective.
And when writing a ton of messages that might be important.