[PATCH] Bluetooth: Fix use after free in l2cap_chan_timeout

There is a potential use after free in bt_sock_poll when a
socket gets killed without getting unlinked from accept_q.
Hence added code to unlink from accpept_q by calling teardown
before freeing the socket for channel type L2CAP_CHAN_CONN_ORIENTED.

Signed-off-by: Harish Jenny K N <redacted>
---
 net/bluetooth/l2cap_core.c |    5 +++++
 1 file changed, 5 insertions(+)

diff --git a/net/bluetooth/l2cap_core.c b/net/bluetooth/l2cap_core.c
index 6ba33f9..c6955fb 100644
--- a/net/bluetooth/l2cap_core.c
+++ b/net/bluetooth/l2cap_core.c

@@ -415,6 +415,11 @@ static void l2cap_chan_timeout(struct work_struct *work)
 
 	l2cap_chan_close(chan, reason);
 
+	if ((chan->state == BT_CONNECTED || chan->state == BT_CONFIG) &&
+	    chan->chan_type == L2CAP_CHAN_CONN_ORIENTED) {
+		chan->ops->teardown(chan, 0);
+	}
+
 	l2cap_chan_unlock(chan);
 
 	chan->ops->close(chan);

-- 
1.7.9.5

Hi,

On Thu, Mar 19, 2015, Harish Jenny K N wrote:

Looks quite ok to me, except for a minor issue: we generally don't use
{} for single-line branches.

Do you have some simple way to reproduce this? It'd be nice if we could
add a test case for it to our user space l2cap-tester tool.

Johan

On Thursday 19 March 2015 01:55 PM, Johan Hedberg wrote:

Hi,

On Thu, Mar 19, 2015, Harish Jenny K N wrote:

quoted

There is a potential use after free in bt_sock_poll when a
socket gets killed without getting unlinked from accept_q.
Hence added code to unlink from accpept_q by calling teardown
before freeing the socket for channel type L2CAP_CHAN_CONN_ORIENTED.

Signed-off-by: Harish Jenny K N <redacted>
---
 net/bluetooth/l2cap_core.c |    5 +++++
 1 file changed, 5 insertions(+)

diff --git a/net/bluetooth/l2cap_core.c b/net/bluetooth/l2cap_core.c
index 6ba33f9..c6955fb 100644
--- a/net/bluetooth/l2cap_core.c
+++ b/net/bluetooth/l2cap_core.c

@@ -415,6 +415,11 @@ static void l2cap_chan_timeout(struct work_struct *work)
 
 	l2cap_chan_close(chan, reason);
 
+	if ((chan->state == BT_CONNECTED || chan->state == BT_CONFIG) &&
+	    chan->chan_type == L2CAP_CHAN_CONN_ORIENTED) {
+		chan->ops->teardown(chan, 0);
+	}

Looks quite ok to me, except for a minor issue: we generally don't use
{} for single-line branches.

Do you have some simple way to reproduce this? It'd be nice if we could
add a test case for it to our user space l2cap-tester tool.

Johan

There is a potential use after free in bt_sock_poll when a
socket gets killed without getting unlinked from accept_q.
Hence added code to unlink from accpept_q by calling teardown
before freeing the socket for channel type L2CAP_CHAN_CONN_ORIENTED.

Signed-off-by: Harish Jenny K N <redacted>
---
 net/bluetooth/l2cap_core.c |    4 ++++
 1 file changed, 4 insertions(+)

diff --git a/net/bluetooth/l2cap_core.c b/net/bluetooth/l2cap_core.c
index 6ba33f9..3e273e6 100644
--- a/net/bluetooth/l2cap_core.c
+++ b/net/bluetooth/l2cap_core.c

@@ -415,6 +415,10 @@ static void l2cap_chan_timeout(struct work_struct *work)
 
 	l2cap_chan_close(chan, reason);
 
+	if ((chan->state == BT_CONNECTED || chan->state == BT_CONFIG) &&
+	    chan->chan_type == L2CAP_CHAN_CONN_ORIENTED)
+		chan->ops->teardown(chan, 0);
+
 	l2cap_chan_unlock(chan);
 
 	chan->ops->close(chan);

On Thursday 19 March 2015 01:55 PM, Johan Hedberg wrote:

Hi,

On Thu, Mar 19, 2015, Harish Jenny K N wrote:

quoted

There is a potential use after free in bt_sock_poll when a
socket gets killed without getting unlinked from accept_q.
Hence added code to unlink from accpept_q by calling teardown
before freeing the socket for channel type L2CAP_CHAN_CONN_ORIENTED.

Signed-off-by: Harish Jenny K N <redacted>
---
 net/bluetooth/l2cap_core.c |    5 +++++
 1 file changed, 5 insertions(+)

diff --git a/net/bluetooth/l2cap_core.c b/net/bluetooth/l2cap_core.c
index 6ba33f9..c6955fb 100644
--- a/net/bluetooth/l2cap_core.c
+++ b/net/bluetooth/l2cap_core.c

@@ -415,6 +415,11 @@ static void l2cap_chan_timeout(struct work_struct *work)
 
 	l2cap_chan_close(chan, reason);
 
+	if ((chan->state == BT_CONNECTED || chan->state == BT_CONFIG) &&
+	    chan->chan_type == L2CAP_CHAN_CONN_ORIENTED) {
+		chan->ops->teardown(chan, 0);
+	}

Looks quite ok to me, except for a minor issue: we generally don't use
{} for single-line branches.

Do you have some simple way to reproduce this? It'd be nice if we could
add a test case for it to our user space l2cap-tester tool.

Johan

Unfortunately no. The crash happened only once in automated test set-up.
Have given only the proposed solution based on the code flow.
Please check from protocol perspective if this patch is correct and useful.

Hello.

On 3/19/2015 11:19 AM, Harish Jenny K N wrote:

There is a potential use after free in bt_sock_poll when a
socket gets killed without getting unlinked from accept_q.
Hence added code to unlink from accpept_q by calling teardown
before freeing the socket for channel type L2CAP_CHAN_CONN_ORIENTED.

Signed-off-by: Harish Jenny K N <redacted>
---
  net/bluetooth/l2cap_core.c |    5 +++++
  1 file changed, 5 insertions(+)

    {} not needed here.

[...]

WBR, Sergei