[PATCH 5.13 076/127] mptcp: fix memory leak on address flush

Sasha Levin
2021-08-24T17:00:59Z

From: Paolo Abeni <pabeni@redhat.com>

[ Upstream commit a0eea5f10eeb5180d115452b0d77afa6603dfe18 ]

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>
Signed-off-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
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 fce1d057d19e..45b414efc001 100644
--- a/net/mptcp/pm_netlink.c
+++ b/net/mptcp/pm_netlink.c
@@ -1135,36 +1135,12 @@ next:
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,
@@ -1244,7 +1220,8 @@ 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;
}
@@ -1297,6 +1274,7 @@ 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)) {
@@ -1305,7 +1283,7 @@ 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);
}
}

@@ -1329,6 +1307,7 @@ 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;
}
@@ -1936,7 +1915,8 @@ 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);
}
--
2.30.2