dom_bef is use to cache current domain record only if current domain
exists. But when current domain does not exist, dom_bef will still be used
in mon_identify_lost_members. This may lead to an information leak.

Fix this by adding a memset before using dom_bef.

Fixes: 35c55c9877f8 ("tipc: add neighbor monitoring framework")
Signed-off-by: Hangyu Hua <hbh25y@gmail.com>
---

v2: remove redundant 'dom_bef.member_cnt = 0;'

 net/tipc/monitor.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/tipc/monitor.c b/net/tipc/monitor.c
index 2f4d23238a7e..03b5d0b65169 100644
--- a/net/tipc/monitor.c
+++ b/net/tipc/monitor.c
@@ -534,7 +534,7 @@ void tipc_mon_rcv(struct net *net, void *data, u16 dlen, u32 addr,
 	state->peer_gen = new_gen;
 
 	/* Cache current domain record for later use */
-	dom_bef.member_cnt = 0;
+	memset(&dom_bef, 0, sizeof(dom_bef));
 	dom = peer->domain;
 	if (dom)
 		memcpy(&dom_bef, dom, dom->len);
-- 
2.25.1

On Tue, 28 Jun 2022 16:31:22 +0800 Hangyu Hua wrote:
> dom_bef is use to cache current domain record only if current domain
> exists. But when current domain does not exist, dom_bef will still be used
> in mon_identify_lost_members. This may lead to an information leak.

AFAICT applied_bef must be zero if peer->domain was 0, so I don't think
mon_identify_lost_members() will do anything.

> Fix this by adding a memset before using dom_bef.
> 
> Fixes: 35c55c9877f8 ("tipc: add neighbor monitoring framework")
> Signed-off-by: Hangyu Hua <hbh25y@gmail.com>

On 2022/6/30 11:31, Jakub Kicinski wrote:
> On Tue, 28 Jun 2022 16:31:22 +0800 Hangyu Hua wrote:
>> dom_bef is use to cache current domain record only if current domain
>> exists. But when current domain does not exist, dom_bef will still be used
>> in mon_identify_lost_members. This may lead to an information leak.
> 
> AFAICT applied_bef must be zero if peer->domain was 0, so I don't think
> mon_identify_lost_members() will do anything.
> 

void tipc_mon_rcv(struct net *net, void *data, u16 dlen, u32 addr,
		  struct tipc_mon_state *state, int bearer_id)
{
...
	if (!dom || (dom->len < new_dlen)) {
		kfree(dom);
		dom = kmalloc(new_dlen, GFP_ATOMIC);	<--- [1]
		peer->domain = dom;
		if (!dom)
			goto exit;
	}
...
}

peer->domain will be NULL when [1] fails. But there will not change 
peer->applied to 0. In this case, if tipc_mon_rcv is called again then 
an information leak will happen.

Thanks,
Hangyu.

>> Fix this by adding a memset before using dom_bef.
>>
>> Fixes: 35c55c9877f8 ("tipc: add neighbor monitoring framework")
>> Signed-off-by: Hangyu Hua <hbh25y@gmail.com>

On Thu, 30 Jun 2022 17:19:21 +0800 Hangyu Hua wrote:
> On 2022/6/30 11:31, Jakub Kicinski wrote:
> > On Tue, 28 Jun 2022 16:31:22 +0800 Hangyu Hua wrote:  
> >> dom_bef is use to cache current domain record only if current domain
> >> exists. But when current domain does not exist, dom_bef will still be used
> >> in mon_identify_lost_members. This may lead to an information leak.  
> > 
> > AFAICT applied_bef must be zero if peer->domain was 0, so I don't think
> > mon_identify_lost_members() will do anything.
> >   
> 
> void tipc_mon_rcv(struct net *net, void *data, u16 dlen, u32 addr,
> 		  struct tipc_mon_state *state, int bearer_id)
> {
> ...
> 	if (!dom || (dom->len < new_dlen)) {
> 		kfree(dom);
> 		dom = kmalloc(new_dlen, GFP_ATOMIC);	<--- [1]
> 		peer->domain = dom;
> 		if (!dom)
> 			goto exit;
> 	}
> ...
> }
> 
> peer->domain will be NULL when [1] fails. But there will not change 
> peer->applied to 0. In this case, if tipc_mon_rcv is called again then 
> an information leak will happen.

I see, good analysis! Jon, Xue - is there a reason domain gets wiped
on memory allocation failure? I'd think we should leave the previous
pointer in place instead of freeing it first.

> -----Original Message-----
> From: Hangyu Hua <hbh25y@gmail.com>
> Sent: Tuesday, June 28, 2022 3:31 PM
> To: jmaloy@redhat.com; ying.xue@windriver.com; davem@davemloft.net; edumazet@google.com; kuba@kernel.org;
> pabeni@redhat.com; Tung Quang Nguyen <tung.q.nguyen@dektech.com.au>
> Cc: netdev@vger.kernel.org; tipc-discussion@lists.sourceforge.net; linux-kernel@vger.kernel.org; Hangyu Hua <hbh25y@gmail.com>
> Subject: [PATCH v2] net: tipc: fix possible infoleak in tipc_mon_rcv()
> 
> dom_bef is use to cache current domain record only if current domain
> exists. But when current domain does not exist, dom_bef will still be used
> in mon_identify_lost_members. This may lead to an information leak.
> 
> Fix this by adding a memset before using dom_bef.
> 
> Fixes: 35c55c9877f8 ("tipc: add neighbor monitoring framework")
> Signed-off-by: Hangyu Hua <hbh25y@gmail.com>
> ---
> 
> v2: remove redundant 'dom_bef.member_cnt = 0;'
> 
>  net/tipc/monitor.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/net/tipc/monitor.c b/net/tipc/monitor.c
> index 2f4d23238a7e..03b5d0b65169 100644
> --- a/net/tipc/monitor.c
> +++ b/net/tipc/monitor.c
> @@ -534,7 +534,7 @@ void tipc_mon_rcv(struct net *net, void *data, u16 dlen, u32 addr,
>  	state->peer_gen = new_gen;
> 
>  	/* Cache current domain record for later use */
> -	dom_bef.member_cnt = 0;
> +	memset(&dom_bef, 0, sizeof(dom_bef));
>  	dom = peer->domain;
>  	if (dom)
>  		memcpy(&dom_bef, dom, dom->len);
> --
> 2.25.1
Reviewed-by: Tung Nguyen <tung.q.nguyen@dektech.com.au>