linux-kernel - Re: [syzbot] [mptcp?] KASAN: slab-use-after-free Read in __timer_delete

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Message-ID: <tencent_DF6D237A296523A8E45177687763C6C2B305@qq.com>
Date: Tue,  3 Sep 2024 21:52:36 +0800
From: Edward Adam Davis <eadavis@...com>
To: syzbot+f3a31fb909db9b2a5c4d@...kaller.appspotmail.com
Cc: linux-kernel@...r.kernel.org
Subject: Re: [syzbot] [mptcp?] KASAN: slab-use-after-free Read in __timer_delete_sync

entry need to be protected by pm.lock.

#syz test

diff --git a/net/mptcp/pm_netlink.c b/net/mptcp/pm_netlink.c
index 3e4ad801786f..06a6846e316c 100644
--- a/net/mptcp/pm_netlink.c
+++ b/net/mptcp/pm_netlink.c
@@ -336,11 +336,12 @@ mptcp_pm_del_add_timer(struct mptcp_sock *msk,
 	entry = mptcp_lookup_anno_list_by_saddr(msk, addr);
 	if (entry && (!check_id || entry->addr.id == addr->id))
 		entry->retrans_times = ADD_ADDR_RETRANS_MAX;
-	spin_unlock_bh(&msk->pm.lock);
 
 	if (entry && (!check_id || entry->addr.id == addr->id))
 		sk_stop_timer_sync(sk, &entry->add_timer);
 
+	spin_unlock_bh(&msk->pm.lock);
+
 	return entry;
 }
 
@@ -1637,6 +1638,7 @@ static void mptcp_pm_remove_addrs_and_subflows(struct mptcp_sock *msk,
 	struct mptcp_rm_list alist = { .nr = 0 }, slist = { .nr = 0 };
 	struct mptcp_pm_addr_entry *entry;
 
+	spin_lock_bh(&msk->pm.lock);
 	list_for_each_entry(entry, rm_list, list) {
 		if (slist.nr < MPTCP_RM_IDS_MAX &&
 		    lookup_subflow_by_saddr(&msk->conn_list, &entry->addr))
@@ -1647,7 +1649,6 @@ static void mptcp_pm_remove_addrs_and_subflows(struct mptcp_sock *msk,
 			alist.ids[alist.nr++] = entry->addr.id;
 	}
 
-	spin_lock_bh(&msk->pm.lock);
 	if (alist.nr) {
 		msk->pm.add_addr_signaled -= alist.nr;
 		mptcp_pm_remove_addr(msk, &alist);