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[v3,2/4] Bluetooth: Refcnt drop must be placed last in hci_conn_unlink

Message ID 20230502212527.1662896-2-luiz.dentz@gmail.com
State New
Headers show
Series [v3,1/4] Bluetooth: Fix potential double free caused by hci_conn_unlink | expand

Commit Message

Luiz Augusto von Dentz May 2, 2023, 9:25 p.m. UTC 
From: Ruihan Li <lrh2000@pku.edu.cn>

If hci_conn_put(conn->parent) reduces conn->parent's reference count to
zero, it can immediately deallocate conn->parent. At the same time,
conn->link->list has its head in conn->parent, causing use-after-free
problems in the latter list_del_rcu(&conn->link->list).

This problem can be easily solved by reordering the two operations,
i.e., first performing the list removal with list_del_rcu and then
decreasing the refcnt with hci_conn_put.

Reported-by: Luiz Augusto von Dentz <luiz.dentz@gmail.com>
Closes: https://lore.kernel.org/linux-bluetooth/CABBYNZ+1kce8_RJrLNOXd_8=Mdpb=2bx4Nto-hFORk=qiOkoCg@mail.gmail.com/
Fixes: 06149746e720 ("Bluetooth: hci_conn: Add support for linking multiple hcon")
Signed-off-by: Ruihan Li <lrh2000@pku.edu.cn>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
---
 net/bluetooth/hci_conn.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)
diff mbox series

Patch

diff --git a/net/bluetooth/hci_conn.c b/net/bluetooth/hci_conn.c
index 70e1655a9df6..44d0643fc681 100644
--- a/net/bluetooth/hci_conn.c
+++ b/net/bluetooth/hci_conn.c
@@ -1102,12 +1102,12 @@  static void hci_conn_unlink(struct hci_conn *conn)
 	if (!conn->link)
 		return;
 
-	hci_conn_put(conn->parent);
-	conn->parent = NULL;
-
 	list_del_rcu(&conn->link->list);
 	synchronize_rcu();
 
+	hci_conn_put(conn->parent);
+	conn->parent = NULL;
+
 	kfree(conn->link);
 	conn->link = NULL;
 }