[PATCH mptcp-net v2] mptcp: fix memory leak on address flush

[PATCH mptcp-net v2] mptcp: fix memory leak on address flush

[Paolo Abeni]

The endpoint cleanup path is prone to a memory leak, as reported
by syzkaller:

 BUG: memory leak
 unreferenced object 0xffff88810680ea00 (size 64):
   comm "syz-executor.6", pid 6191, jiffies 4295756280 (age 24.138s)
   hex dump (first 32 bytes):
     58 75 7d 3c 80 88 ff ff 22 01 00 00 00 00 ad de  Xu}<....".......
     01 00 02 00 00 00 00 00 ac 1e 00 07 00 00 00 00  ................
   backtrace:
     [<0000000072a9f72a>] kmalloc include/linux/slab.h:591 [inline]
     [<0000000072a9f72a>] mptcp_nl_cmd_add_addr+0x287/0x9f0 net/mptcp/pm_netlink.c:1170
     [<00000000f6e931bf>] genl_family_rcv_msg_doit.isra.0+0x225/0x340 net/netlink/genetlink.c:731
     [<00000000f1504a2c>] genl_family_rcv_msg net/netlink/genetlink.c:775 [inline]
     [<00000000f1504a2c>] genl_rcv_msg+0x341/0x5b0 net/netlink/genetlink.c:792
     [<0000000097e76f6a>] netlink_rcv_skb+0x148/0x430 net/netlink/af_netlink.c:2504
     [<00000000ceefa2b8>] genl_rcv+0x24/0x40 net/netlink/genetlink.c:803
     [<000000008ff91aec>] netlink_unicast_kernel net/netlink/af_netlink.c:1314 [inline]
     [<000000008ff91aec>] netlink_unicast+0x537/0x750 net/netlink/af_netlink.c:1340
     [<0000000041682c35>] netlink_sendmsg+0x846/0xd80 net/netlink/af_netlink.c:1929
     [<00000000df3aa8e7>] sock_sendmsg_nosec net/socket.c:704 [inline]
     [<00000000df3aa8e7>] sock_sendmsg+0x14e/0x190 net/socket.c:724
     [<000000002154c54c>] ____sys_sendmsg+0x709/0x870 net/socket.c:2403
     [<000000001aab01d7>] ___sys_sendmsg+0xff/0x170 net/socket.c:2457
     [<00000000fa3b1446>] __sys_sendmsg+0xe5/0x1b0 net/socket.c:2486
     [<00000000db2ee9c7>] do_syscall_x64 arch/x86/entry/common.c:50 [inline]
     [<00000000db2ee9c7>] do_syscall_64+0x38/0x90 arch/x86/entry/common.c:80
     [<000000005873517d>] entry_SYSCALL_64_after_hwframe+0x44/0xae

We should not require an allocation to cleanup stuff.

Rework the code a bit so that the additional RCU work is no more needed.

Fixes: 1729cf186d8a ("mptcp: create the listening socket for new port")
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
---
v1 -> v2:
 - remove unused addr_entry_release_work definition, too - Mat
---
 net/mptcp/pm_netlink.c | 44 ++++++++++++------------------------------
 1 file changed, 12 insertions(+), 32 deletions(-)

diff --git a/net/mptcp/pm_netlink.c b/net/mptcp/pm_netlink.c
index 371607dc6ff7..1e4289c507ff 100644
--- a/net/mptcp/pm_netlink.c
+++ b/net/mptcp/pm_netlink.c
@@ -1295,36 +1295,12 @@ static int mptcp_nl_remove_subflow_and_signal_addr(struct net *net,
 	return 0;
 }
 
-struct addr_entry_release_work {
-	struct rcu_work	rwork;
-	struct mptcp_pm_addr_entry *entry;
-};
-
-static void mptcp_pm_release_addr_entry(struct work_struct *work)
+/* caller must ensure the RCU grace period is already elapsed */
+static void __mptcp_pm_release_addr_entry(struct mptcp_pm_addr_entry *entry)
 {
-	struct addr_entry_release_work *w;
-	struct mptcp_pm_addr_entry *entry;
-
-	w = container_of(to_rcu_work(work), struct addr_entry_release_work, rwork);
-	entry = w->entry;
-	if (entry) {
-		if (entry->lsk)
-			sock_release(entry->lsk);
-		kfree(entry);
-	}
-	kfree(w);
-}
-
-static void mptcp_pm_free_addr_entry(struct mptcp_pm_addr_entry *entry)
-{
-	struct addr_entry_release_work *w;
-
-	w = kmalloc(sizeof(*w), GFP_ATOMIC);
-	if (w) {
-		INIT_RCU_WORK(&w->rwork, mptcp_pm_release_addr_entry);
-		w->entry = entry;
-		queue_rcu_work(system_wq, &w->rwork);
-	}
+	if (entry->lsk)
+		sock_release(entry->lsk);
+	kfree(entry);
 }
 
 static int mptcp_nl_remove_id_zero_address(struct net *net,
@@ -1404,7 +1380,8 @@ static int mptcp_nl_cmd_del_addr(struct sk_buff *skb, struct genl_info *info)
 	spin_unlock_bh(&pernet->lock);
 
 	mptcp_nl_remove_subflow_and_signal_addr(sock_net(skb->sk), &entry->addr);
-	mptcp_pm_free_addr_entry(entry);
+	synchronize_rcu();
+	__mptcp_pm_release_addr_entry(entry);
 
 	return ret;
 }
@@ -1457,6 +1434,7 @@ static void mptcp_nl_remove_addrs_list(struct net *net,
 	}
 }
 
+/* caller must ensure the RCU grace period is already elapsed */
 static void __flush_addrs(struct list_head *list)
 {
 	while (!list_empty(list)) {
@@ -1465,7 +1443,7 @@ static void __flush_addrs(struct list_head *list)
 		cur = list_entry(list->next,
 				 struct mptcp_pm_addr_entry, list);
 		list_del_rcu(&cur->list);
-		mptcp_pm_free_addr_entry(cur);
+		__mptcp_pm_release_addr_entry(cur);
 	}
 }
 
@@ -1489,6 +1467,7 @@ static int mptcp_nl_cmd_flush_addrs(struct sk_buff *skb, struct genl_info *info)
 	bitmap_zero(pernet->id_bitmap, MAX_ADDR_ID + 1);
 	spin_unlock_bh(&pernet->lock);
 	mptcp_nl_remove_addrs_list(sock_net(skb->sk), &free_list);
+	synchronize_rcu();
 	__flush_addrs(&free_list);
 	return 0;
 }
@@ -2100,7 +2079,8 @@ static void __net_exit pm_nl_exit_net(struct list_head *net_list)
 		struct pm_nl_pernet *pernet = net_generic(net, pm_nl_pernet_id);
 
 		/* net is removed from namespace list, can't race with
-		 * other modifiers
+		 * other modifiers, also netns core already waited for a
+		 * RCU grace period.
 		 */
 		__flush_addrs(&pernet->local_addr_list);
 	}
-- 
2.26.3

Re: [PATCH mptcp-net v2] mptcp: fix memory leak on address flush

[Mat Martineau]

On Fri, 13 Aug 2021, Paolo Abeni wrote:

> The endpoint cleanup path is prone to a memory leak, as reported
> by syzkaller:
>
> BUG: memory leak
> unreferenced object 0xffff88810680ea00 (size 64):
>   comm "syz-executor.6", pid 6191, jiffies 4295756280 (age 24.138s)
>   hex dump (first 32 bytes):
>     58 75 7d 3c 80 88 ff ff 22 01 00 00 00 00 ad de  Xu}<....".......
>     01 00 02 00 00 00 00 00 ac 1e 00 07 00 00 00 00  ................
>   backtrace:
>     [<0000000072a9f72a>] kmalloc include/linux/slab.h:591 [inline]
>     [<0000000072a9f72a>] mptcp_nl_cmd_add_addr+0x287/0x9f0 net/mptcp/pm_netlink.c:1170
>     [<00000000f6e931bf>] genl_family_rcv_msg_doit.isra.0+0x225/0x340 net/netlink/genetlink.c:731
>     [<00000000f1504a2c>] genl_family_rcv_msg net/netlink/genetlink.c:775 [inline]
>     [<00000000f1504a2c>] genl_rcv_msg+0x341/0x5b0 net/netlink/genetlink.c:792
>     [<0000000097e76f6a>] netlink_rcv_skb+0x148/0x430 net/netlink/af_netlink.c:2504
>     [<00000000ceefa2b8>] genl_rcv+0x24/0x40 net/netlink/genetlink.c:803
>     [<000000008ff91aec>] netlink_unicast_kernel net/netlink/af_netlink.c:1314 [inline]
>     [<000000008ff91aec>] netlink_unicast+0x537/0x750 net/netlink/af_netlink.c:1340
>     [<0000000041682c35>] netlink_sendmsg+0x846/0xd80 net/netlink/af_netlink.c:1929
>     [<00000000df3aa8e7>] sock_sendmsg_nosec net/socket.c:704 [inline]
>     [<00000000df3aa8e7>] sock_sendmsg+0x14e/0x190 net/socket.c:724
>     [<000000002154c54c>] ____sys_sendmsg+0x709/0x870 net/socket.c:2403
>     [<000000001aab01d7>] ___sys_sendmsg+0xff/0x170 net/socket.c:2457
>     [<00000000fa3b1446>] __sys_sendmsg+0xe5/0x1b0 net/socket.c:2486
>     [<00000000db2ee9c7>] do_syscall_x64 arch/x86/entry/common.c:50 [inline]
>     [<00000000db2ee9c7>] do_syscall_64+0x38/0x90 arch/x86/entry/common.c:80
>     [<000000005873517d>] entry_SYSCALL_64_after_hwframe+0x44/0xae
>
> We should not require an allocation to cleanup stuff.
>
> Rework the code a bit so that the additional RCU work is no more needed.
>
> Fixes: 1729cf186d8a ("mptcp: create the listening socket for new port")
> Signed-off-by: Paolo Abeni <pabeni@redhat.com>
> ---
> v1 -> v2:
> - remove unused addr_entry_release_work definition, too - Mat

Thanks for the v2 Paolo, looks good to me:

Reviewed-by: Mat Martineau <mathew.j.martineau@linux.intel.com>


> ---
> net/mptcp/pm_netlink.c | 44 ++++++++++++------------------------------
> 1 file changed, 12 insertions(+), 32 deletions(-)
>
> diff --git a/net/mptcp/pm_netlink.c b/net/mptcp/pm_netlink.c
> index 371607dc6ff7..1e4289c507ff 100644
> --- a/net/mptcp/pm_netlink.c
> +++ b/net/mptcp/pm_netlink.c
> @@ -1295,36 +1295,12 @@ static int mptcp_nl_remove_subflow_and_signal_addr(struct net *net,
> 	return 0;
> }
>
> -struct addr_entry_release_work {
> -	struct rcu_work	rwork;
> -	struct mptcp_pm_addr_entry *entry;
> -};
> -
> -static void mptcp_pm_release_addr_entry(struct work_struct *work)
> +/* caller must ensure the RCU grace period is already elapsed */
> +static void __mptcp_pm_release_addr_entry(struct mptcp_pm_addr_entry *entry)
> {
> -	struct addr_entry_release_work *w;
> -	struct mptcp_pm_addr_entry *entry;
> -
> -	w = container_of(to_rcu_work(work), struct addr_entry_release_work, rwork);
> -	entry = w->entry;
> -	if (entry) {
> -		if (entry->lsk)
> -			sock_release(entry->lsk);
> -		kfree(entry);
> -	}
> -	kfree(w);
> -}
> -
> -static void mptcp_pm_free_addr_entry(struct mptcp_pm_addr_entry *entry)
> -{
> -	struct addr_entry_release_work *w;
> -
> -	w = kmalloc(sizeof(*w), GFP_ATOMIC);
> -	if (w) {
> -		INIT_RCU_WORK(&w->rwork, mptcp_pm_release_addr_entry);
> -		w->entry = entry;
> -		queue_rcu_work(system_wq, &w->rwork);
> -	}
> +	if (entry->lsk)
> +		sock_release(entry->lsk);
> +	kfree(entry);
> }
>
> static int mptcp_nl_remove_id_zero_address(struct net *net,
> @@ -1404,7 +1380,8 @@ static int mptcp_nl_cmd_del_addr(struct sk_buff *skb, struct genl_info *info)
> 	spin_unlock_bh(&pernet->lock);
>
> 	mptcp_nl_remove_subflow_and_signal_addr(sock_net(skb->sk), &entry->addr);
> -	mptcp_pm_free_addr_entry(entry);
> +	synchronize_rcu();
> +	__mptcp_pm_release_addr_entry(entry);
>
> 	return ret;
> }
> @@ -1457,6 +1434,7 @@ static void mptcp_nl_remove_addrs_list(struct net *net,
> 	}
> }
>
> +/* caller must ensure the RCU grace period is already elapsed */
> static void __flush_addrs(struct list_head *list)
> {
> 	while (!list_empty(list)) {
> @@ -1465,7 +1443,7 @@ static void __flush_addrs(struct list_head *list)
> 		cur = list_entry(list->next,
> 				 struct mptcp_pm_addr_entry, list);
> 		list_del_rcu(&cur->list);
> -		mptcp_pm_free_addr_entry(cur);
> +		__mptcp_pm_release_addr_entry(cur);
> 	}
> }
>
> @@ -1489,6 +1467,7 @@ static int mptcp_nl_cmd_flush_addrs(struct sk_buff *skb, struct genl_info *info)
> 	bitmap_zero(pernet->id_bitmap, MAX_ADDR_ID + 1);
> 	spin_unlock_bh(&pernet->lock);
> 	mptcp_nl_remove_addrs_list(sock_net(skb->sk), &free_list);
> +	synchronize_rcu();
> 	__flush_addrs(&free_list);
> 	return 0;
> }
> @@ -2100,7 +2079,8 @@ static void __net_exit pm_nl_exit_net(struct list_head *net_list)
> 		struct pm_nl_pernet *pernet = net_generic(net, pm_nl_pernet_id);
>
> 		/* net is removed from namespace list, can't race with
> -		 * other modifiers
> +		 * other modifiers, also netns core already waited for a
> +		 * RCU grace period.
> 		 */
> 		__flush_addrs(&pernet->local_addr_list);
> 	}
> -- 
> 2.26.3
>
>
>

--
Mat Martineau
Intel

Re: [PATCH mptcp-net v2] mptcp: fix memory leak on address flush

[Matthieu Baerts]

Hi Paolo, Mat,

On 13/08/2021 16:05, Paolo Abeni wrote:
> The endpoint cleanup path is prone to a memory leak, as reported
> by syzkaller:

Thank you for this patch and the review!

Now in our tree (net) with Mat's tag:

- bbffcd9faae3: mptcp: fix memory leak on address flush
- Results: a5b32fb5c3ca..55f3937bfef4

Builds and tests are now in progress:

https://cirrus-ci.com/github/multipath-tcp/mptcp_net-next/export/20210816T173103
https://github.com/multipath-tcp/mptcp_net-next/actions/workflows/build-validation.yml?query=branch:export/20210816T173103

Cheers,
Matt
-- 
Tessares | Belgium | Hybrid Access Solutions
www.tessares.net

Re: [PATCH mptcp-net v2] mptcp: fix memory leak on address flush

[Geliang Tang]

Matthieu Baerts <matthieu.baerts@tessares.net> 于2021年8月17日周二 上午1:31写道：
>
> Hi Paolo, Mat,
>
> On 13/08/2021 16:05, Paolo Abeni wrote:
> > The endpoint cleanup path is prone to a memory leak, as reported
> > by syzkaller:
>
> Thank you for this patch and the review!
>
> Now in our tree (net) with Mat's tag:
>
> - bbffcd9faae3: mptcp: fix memory leak on address flush
> - Results: a5b32fb5c3ca..55f3937bfef4
>
> Builds and tests are now in progress:

Hi Matt,

I think we can close issue #223 now.

Thanks,
-Geliang

>
> https://cirrus-ci.com/github/multipath-tcp/mptcp_net-next/export/20210816T173103
> https://github.com/multipath-tcp/mptcp_net-next/actions/workflows/build-validation.yml?query=branch:export/20210816T173103
>
> Cheers,
> Matt
> --
> Tessares | Belgium | Hybrid Access Solutions
> www.tessares.net

Re: [PATCH mptcp-net v2] mptcp: fix memory leak on address flush

[Matthieu Baerts]

Hi Geliang,

On 18/08/2021 05:16, Geliang Tang wrote:
> Matthieu Baerts <matthieu.baerts@tessares.net> 于2021年8月17日周二 上午1:31写道：
>>
>> Hi Paolo, Mat,
>>
>> On 13/08/2021 16:05, Paolo Abeni wrote:
>>> The endpoint cleanup path is prone to a memory leak, as reported
>>> by syzkaller:
>>
>> Thank you for this patch and the review!
>>
>> Now in our tree (net) with Mat's tag:
>>
>> - bbffcd9faae3: mptcp: fix memory leak on address flush
>> - Results: a5b32fb5c3ca..55f3937bfef4
>>
>> Builds and tests are now in progress:
> 
> Hi Matt,
> 
> I think we can close issue #223 now.

Good point, I didn't notice the 'Closes' tag was missing.
I just closed this ticket.

Cheers,
Matt
-- 
Tessares | Belgium | Hybrid Access Solutions
www.tessares.net