linux-kernel - [PATCH v5 6/6] Bluetooth: fix repeated calls to sco_sock

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Message-Id: <20210804110308.910744-7-desmondcheongzx@gmail.com>
Date:   Wed,  4 Aug 2021 19:03:08 +0800
From:   Desmond Cheong Zhi Xi <desmondcheongzx@...il.com>
To:     marcel@...tmann.org, johan.hedberg@...il.com, luiz.dentz@...il.com,
        davem@...emloft.net, kuba@...nel.org, sudipm.mukherjee@...il.com
Cc:     Desmond Cheong Zhi Xi <desmondcheongzx@...il.com>,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        skhan@...uxfoundation.org, gregkh@...uxfoundation.org,
        linux-kernel-mentees@...ts.linuxfoundation.org
Subject: [PATCH v5 6/6] Bluetooth: fix repeated calls to sco_sock_kill

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
sco_sock_release.

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@...il.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;
 	sk->sk_state_change(sk);
 	release_sock(sk);
-
-	sco_sock_kill(sk);
 	sock_put(sk);
 }

@@ -203,7 +201,6 @@ static void sco_conn_del(struct hci_conn *hcon, int err)
 		sco_sock_clear_timer(sk);
 		sco_chan_del(sk, err);
 		release_sock(sk);
-		sco_sock_kill(sk);
 		sock_put(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)
 		return;

 	BT_DBG("sk %p state %d", sk, sk->sk_state);
@@ -463,7 +459,6 @@ static void sco_sock_close(struct sock *sk)
 	sco_sock_clear_timer(sk);
 	__sco_sock_close(sk);
 	release_sock(sk);
-	sco_sock_kill(sk);
 }

 static void sco_skb_put_cmsg(struct sk_buff *skb, struct msghdr *msg,
-- 
2.25.1