[RESEND PATCH v5 6/6] Bluetooth: fix repeated calls to sco_sock_kill

Desmond Cheong Zhi Xi desmondcheongzx at gmail.com
Wed Aug 4 15:47:12 UTC 2021

In commit 4e1a720d0312 ("Bluetooth: avoid killing an already killed
socket"), a check was added to sco_sock_kill to skip killing a socket
if the SOCK_DEAD flag was set.

This was done after a trace for a use-after-free bug showed that the
same sock pointer was being killed twice.

Unfortunately, this check prevents sco_sock_kill from running on any
socket. sco_sock_kill kills a socket only if it's zapped and orphaned,
however sock_orphan announces that the socket is dead before detaching
it. i.e., orphaned sockets have the SOCK_DEAD flag set.

To fix this, we remove the check for SOCK_DEAD, and avoid repeated
calls to sco_sock_kill by removing incorrect calls in:

1. sco_sock_timeout. The socket should not be killed on timeout as
further processing is expected to be done. For example,
sco_sock_connect sets the timer then waits for the socket to be
connected or for an error to be returned.

2. sco_conn_del. This function should clean up resources for the
connection, but the socket itself should be cleaned up in

3. sco_sock_close. Calls to sco_sock_close in sco_sock_cleanup_listen
and sco_sock_release are followed by sco_sock_kill. Hence the
duplicated call should be removed.

Fixes: 4e1a720d0312 ("Bluetooth: avoid killing an already killed socket")
Signed-off-by: Desmond Cheong Zhi Xi <desmondcheongzx at gmail.com>
 net/bluetooth/sco.c | 7 +------
 1 file changed, 1 insertion(+), 6 deletions(-)

diff --git a/net/bluetooth/sco.c b/net/bluetooth/sco.c
index 418543c390b3..cf43ccb50573 100644
--- a/net/bluetooth/sco.c
+++ b/net/bluetooth/sco.c
@@ -97,8 +97,6 @@ static void sco_sock_timeout(struct work_struct *work)
 	sk->sk_err = ETIMEDOUT;
-	sco_sock_kill(sk);
@@ -203,7 +201,6 @@ static void sco_conn_del(struct hci_conn *hcon, int err)
 		sco_chan_del(sk, err);
-		sco_sock_kill(sk);
 		/* Ensure no more work items will run before freeing conn. */
@@ -410,8 +407,7 @@ static void sco_sock_cleanup_listen(struct sock *parent)
 static void sco_sock_kill(struct sock *sk)
-	if (!sock_flag(sk, SOCK_ZAPPED) || sk->sk_socket ||
-	    sock_flag(sk, SOCK_DEAD))
+	if (!sock_flag(sk, SOCK_ZAPPED) || sk->sk_socket)
 	BT_DBG("sk %p state %d", sk, sk->sk_state);
@@ -463,7 +459,6 @@ static void sco_sock_close(struct sock *sk)
-	sco_sock_kill(sk);
 static void sco_skb_put_cmsg(struct sk_buff *skb, struct msghdr *msg,

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