Bluetooth: L2CAP: Fix use-after-free caused by l2cap_chan_put

This fixes the following trace which is caused by hci_rx_work starting up
*after* the final channel reference has been put() during sock_close() but
*before* the references to the channel have been destroyed, so instead
the code now rely on kref_get_unless_zero/l2cap_chan_hold_unless_zero to
prevent referencing a channel that is about to be destroyed.

  refcount_t: increment on 0; use-after-free.
  BUG: KASAN: use-after-free in refcount_dec_and_test+0x20/0xd0
  Read of size 4 at addr ffffffc114f5bf18 by task kworker/u17:14/705

  CPU: 4 PID: 705 Comm: kworker/u17:14 Tainted: G S      W
  4.14.234-00003-g1fb6d0bd49a4-dirty #28
  Hardware name: Qualcomm Technologies, Inc. SM8150 V2 PM8150
  Google Inc. MSM sm8150 Flame DVT (DT)
  Workqueue: hci0 hci_rx_work
  Call trace:
   dump_backtrace+0x0/0x378
   show_stack+0x20/0x2c
   dump_stack+0x124/0x148
   print_address_description+0x80/0x2e8
   __kasan_report+0x168/0x188
   kasan_report+0x10/0x18
   __asan_load4+0x84/0x8c
   refcount_dec_and_test+0x20/0xd0
   l2cap_chan_put+0x48/0x12c
   l2cap_recv_frame+0x4770/0x6550
   l2cap_recv_acldata+0x44c/0x7a4
   hci_acldata_packet+0x100/0x188
   hci_rx_work+0x178/0x23c
   process_one_work+0x35c/0x95c
   worker_thread+0x4cc/0x960
   kthread+0x1a8/0x1c4
   ret_from_fork+0x10/0x18

Cc: stable@kernel.org
Reported-by: default avatarLee Jones <lee.jones@linaro.org>
Signed-off-by: default avatarLuiz Augusto von Dentz <luiz.von.dentz@intel.com>
Tested-by: default avatarLee Jones <lee.jones@linaro.org>
Signed-off-by: default avatarLuiz Augusto von Dentz <luiz.von.dentz@intel.com>
parent ef61b6ea
......@@ -847,6 +847,7 @@ enum {
};
void l2cap_chan_hold(struct l2cap_chan *c);
struct l2cap_chan *l2cap_chan_hold_unless_zero(struct l2cap_chan *c);
void l2cap_chan_put(struct l2cap_chan *c);
static inline void l2cap_chan_lock(struct l2cap_chan *chan)
......
......@@ -111,7 +111,8 @@ static struct l2cap_chan *__l2cap_get_chan_by_scid(struct l2cap_conn *conn,
}
/* Find channel with given SCID.
* Returns locked channel. */
* Returns a reference locked channel.
*/
static struct l2cap_chan *l2cap_get_chan_by_scid(struct l2cap_conn *conn,
u16 cid)
{
......@@ -119,15 +120,19 @@ static struct l2cap_chan *l2cap_get_chan_by_scid(struct l2cap_conn *conn,
mutex_lock(&conn->chan_lock);
c = __l2cap_get_chan_by_scid(conn, cid);
if (c)
l2cap_chan_lock(c);
if (c) {
/* Only lock if chan reference is not 0 */
c = l2cap_chan_hold_unless_zero(c);
if (c)
l2cap_chan_lock(c);
}
mutex_unlock(&conn->chan_lock);
return c;
}
/* Find channel with given DCID.
* Returns locked channel.
* Returns a reference locked channel.
*/
static struct l2cap_chan *l2cap_get_chan_by_dcid(struct l2cap_conn *conn,
u16 cid)
......@@ -136,8 +141,12 @@ static struct l2cap_chan *l2cap_get_chan_by_dcid(struct l2cap_conn *conn,
mutex_lock(&conn->chan_lock);
c = __l2cap_get_chan_by_dcid(conn, cid);
if (c)
l2cap_chan_lock(c);
if (c) {
/* Only lock if chan reference is not 0 */
c = l2cap_chan_hold_unless_zero(c);
if (c)
l2cap_chan_lock(c);
}
mutex_unlock(&conn->chan_lock);
return c;
......@@ -162,8 +171,12 @@ static struct l2cap_chan *l2cap_get_chan_by_ident(struct l2cap_conn *conn,
mutex_lock(&conn->chan_lock);
c = __l2cap_get_chan_by_ident(conn, ident);
if (c)
l2cap_chan_lock(c);
if (c) {
/* Only lock if chan reference is not 0 */
c = l2cap_chan_hold_unless_zero(c);
if (c)
l2cap_chan_lock(c);
}
mutex_unlock(&conn->chan_lock);
return c;
......@@ -497,6 +510,16 @@ void l2cap_chan_hold(struct l2cap_chan *c)
kref_get(&c->kref);
}
struct l2cap_chan *l2cap_chan_hold_unless_zero(struct l2cap_chan *c)
{
BT_DBG("chan %p orig refcnt %u", c, kref_read(&c->kref));
if (!kref_get_unless_zero(&c->kref))
return NULL;
return c;
}
void l2cap_chan_put(struct l2cap_chan *c)
{
BT_DBG("chan %p orig refcnt %u", c, kref_read(&c->kref));
......@@ -1968,7 +1991,10 @@ static struct l2cap_chan *l2cap_global_chan_by_psm(int state, __le16 psm,
src_match = !bacmp(&c->src, src);
dst_match = !bacmp(&c->dst, dst);
if (src_match && dst_match) {
l2cap_chan_hold(c);
c = l2cap_chan_hold_unless_zero(c);
if (!c)
continue;
read_unlock(&chan_list_lock);
return c;
}
......@@ -1983,7 +2009,7 @@ static struct l2cap_chan *l2cap_global_chan_by_psm(int state, __le16 psm,
}
if (c1)
l2cap_chan_hold(c1);
c1 = l2cap_chan_hold_unless_zero(c1);
read_unlock(&chan_list_lock);
......@@ -4463,6 +4489,7 @@ static inline int l2cap_config_req(struct l2cap_conn *conn,
unlock:
l2cap_chan_unlock(chan);
l2cap_chan_put(chan);
return err;
}
......@@ -4577,6 +4604,7 @@ static inline int l2cap_config_rsp(struct l2cap_conn *conn,
done:
l2cap_chan_unlock(chan);
l2cap_chan_put(chan);
return err;
}
......@@ -5304,6 +5332,7 @@ static inline int l2cap_move_channel_req(struct l2cap_conn *conn,
l2cap_send_move_chan_rsp(chan, result);
l2cap_chan_unlock(chan);
l2cap_chan_put(chan);
return 0;
}
......@@ -5396,6 +5425,7 @@ static void l2cap_move_continue(struct l2cap_conn *conn, u16 icid, u16 result)
}
l2cap_chan_unlock(chan);
l2cap_chan_put(chan);
}
static void l2cap_move_fail(struct l2cap_conn *conn, u8 ident, u16 icid,
......@@ -5425,6 +5455,7 @@ static void l2cap_move_fail(struct l2cap_conn *conn, u8 ident, u16 icid,
l2cap_send_move_chan_cfm(chan, L2CAP_MC_UNCONFIRMED);
l2cap_chan_unlock(chan);
l2cap_chan_put(chan);
}
static int l2cap_move_channel_rsp(struct l2cap_conn *conn,
......@@ -5488,6 +5519,7 @@ static int l2cap_move_channel_confirm(struct l2cap_conn *conn,
l2cap_send_move_chan_cfm_rsp(conn, cmd->ident, icid);
l2cap_chan_unlock(chan);
l2cap_chan_put(chan);
return 0;
}
......@@ -5523,6 +5555,7 @@ static inline int l2cap_move_channel_confirm_rsp(struct l2cap_conn *conn,
}
l2cap_chan_unlock(chan);
l2cap_chan_put(chan);
return 0;
}
......@@ -5895,12 +5928,11 @@ static inline int l2cap_le_credits(struct l2cap_conn *conn,
if (credits > max_credits) {
BT_ERR("LE credits overflow");
l2cap_send_disconn_req(chan, ECONNRESET);
l2cap_chan_unlock(chan);
/* Return 0 so that we don't trigger an unnecessary
* command reject packet.
*/
return 0;
goto unlock;
}
chan->tx_credits += credits;
......@@ -5911,7 +5943,9 @@ static inline int l2cap_le_credits(struct l2cap_conn *conn,
if (chan->tx_credits)
chan->ops->resume(chan);
unlock:
l2cap_chan_unlock(chan);
l2cap_chan_put(chan);
return 0;
}
......@@ -7597,6 +7631,7 @@ static void l2cap_data_channel(struct l2cap_conn *conn, u16 cid,
done:
l2cap_chan_unlock(chan);
l2cap_chan_put(chan);
}
static void l2cap_conless_channel(struct l2cap_conn *conn, __le16 psm,
......@@ -8085,7 +8120,7 @@ static struct l2cap_chan *l2cap_global_fixed_chan(struct l2cap_chan *c,
if (src_type != c->src_type)
continue;
l2cap_chan_hold(c);
c = l2cap_chan_hold_unless_zero(c);
read_unlock(&chan_list_lock);
return c;
}
......
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