diff mbox series

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

Message ID 20220720170648.148219-1-luiz.dentz@gmail.com
State Superseded
Headers show
Series Bluetooth: L2CAP: Fix use-after-free caused by l2cap_chan_put | expand

Commit Message

Luiz Augusto von Dentz July 20, 2022, 5:06 p.m. UTC 
From: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>

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
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
---
 include/net/bluetooth/l2cap.h |  1 +
 net/bluetooth/l2cap_core.c    | 61 +++++++++++++++++++++++++++--------
 2 files changed, 49 insertions(+), 13 deletions(-)

Comments

bluez.test.bot@gmail.com July 20, 2022, 6:13 p.m. UTC | #1 
This is automated email and please do not reply to this email!

Dear submitter,

Thank you for submitting the patches to the linux bluetooth mailing list.
This is a CI test results with your patch series:
PW Link:https://patchwork.kernel.org/project/bluetooth/list/?series=661544

---Test result---

Test Summary:
CheckPatch                    PASS      1.49 seconds
GitLint                       PASS      0.49 seconds
SubjectPrefix                 PASS      0.31 seconds
BuildKernel                   PASS      45.10 seconds
BuildKernel32                 PASS      38.60 seconds
Incremental Build with patchesPASS      54.60 seconds
TestRunner: Setup             PASS      661.14 seconds
TestRunner: l2cap-tester      PASS      19.94 seconds
TestRunner: bnep-tester       PASS      7.38 seconds
TestRunner: mgmt-tester       PASS      122.17 seconds
TestRunner: rfcomm-tester     PASS      11.24 seconds
TestRunner: sco-tester        PASS      11.31 seconds
TestRunner: smp-tester        PASS      11.12 seconds
TestRunner: userchan-tester   PASS      7.22 seconds



---
Regards,
Linux Bluetooth
Lee Jones July 21, 2022, 7:43 a.m. UTC | #2 
On Wed, 20 Jul 2022, Luiz Augusto von Dentz wrote:

> From: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
> 
> 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
> Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
> Signed-off-by: Lee Jones <lee.jones@linaro.org>

Signed-off-by isn't the correct tag for this since I wasn't
responsible for any of the coding, nor am I in the merge path.

Either as a v2 or when the patch is applied, please swap out for:

Reported-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
Tested-by: Lee Jones <lee.jones@linaro.org>

> ---
>  include/net/bluetooth/l2cap.h |  1 +
>  net/bluetooth/l2cap_core.c    | 61 +++++++++++++++++++++++++++--------
>  2 files changed, 49 insertions(+), 13 deletions(-)
> 
> diff --git a/include/net/bluetooth/l2cap.h b/include/net/bluetooth/l2cap.h
> index 3c4f550e5a8b..2f766e3437ce 100644
> --- a/include/net/bluetooth/l2cap.h
> +++ b/include/net/bluetooth/l2cap.h
> @@ -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)
> diff --git a/net/bluetooth/l2cap_core.c b/net/bluetooth/l2cap_core.c
> index 09ecaf556de5..77c0aac14539 100644
> --- a/net/bluetooth/l2cap_core.c
> +++ b/net/bluetooth/l2cap_core.c
> @@ -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));
> @@ -1969,7 +1992,10 @@ 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;
>  			}
> @@ -1984,7 +2010,7 @@ 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);
>  
> @@ -4464,6 +4490,7 @@ static inline int l2cap_config_req(struct l2cap_conn *conn,
>  
>  unlock:
>  	l2cap_chan_unlock(chan);
> +	l2cap_chan_put(chan);
>  	return err;
>  }
>  
> @@ -4578,6 +4605,7 @@ static inline int l2cap_config_rsp(struct l2cap_conn *conn,
>  
>  done:
>  	l2cap_chan_unlock(chan);
> +	l2cap_chan_put(chan);
>  	return err;
>  }
>  
> @@ -5305,6 +5333,7 @@ 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;
>  }
> @@ -5397,6 +5426,7 @@ 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,
> @@ -5426,6 +5456,7 @@ 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,
> @@ -5489,6 +5520,7 @@ 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;
>  }
> @@ -5524,6 +5556,7 @@ static inline int l2cap_move_channel_confirm_rsp(struct l2cap_conn *conn,
>  	}
>  
>  	l2cap_chan_unlock(chan);
> +	l2cap_chan_put(chan);
>  
>  	return 0;
>  }
> @@ -5896,12 +5929,11 @@ 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;
> @@ -5912,7 +5944,9 @@ 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;
>  }
> @@ -7598,6 +7632,7 @@ 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,
> @@ -8086,7 +8121,7 @@ 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;
>  	}
Luiz Augusto von Dentz July 21, 2022, 4:11 p.m. UTC | #3 
Hi Lee,

On Thu, Jul 21, 2022 at 12:43 AM Lee Jones <lee.jones@linaro.org> wrote:
>
> On Wed, 20 Jul 2022, Luiz Augusto von Dentz wrote:
>
> > From: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
> >
> > 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
> > Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
> > Signed-off-by: Lee Jones <lee.jones@linaro.org>
>
> Signed-off-by isn't the correct tag for this since I wasn't
> responsible for any of the coding, nor am I in the merge path.
>
> Either as a v2 or when the patch is applied, please swap out for:
>
> Reported-by: Lee Jones <lee.jones@linaro.org>
> Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
> Tested-by: Lee Jones <lee.jones@linaro.org>

v2 sent.

> > ---
> >  include/net/bluetooth/l2cap.h |  1 +
> >  net/bluetooth/l2cap_core.c    | 61 +++++++++++++++++++++++++++--------
> >  2 files changed, 49 insertions(+), 13 deletions(-)
> >
> > diff --git a/include/net/bluetooth/l2cap.h b/include/net/bluetooth/l2cap.h
> > index 3c4f550e5a8b..2f766e3437ce 100644
> > --- a/include/net/bluetooth/l2cap.h
> > +++ b/include/net/bluetooth/l2cap.h
> > @@ -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)
> > diff --git a/net/bluetooth/l2cap_core.c b/net/bluetooth/l2cap_core.c
> > index 09ecaf556de5..77c0aac14539 100644
> > --- a/net/bluetooth/l2cap_core.c
> > +++ b/net/bluetooth/l2cap_core.c
> > @@ -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));
> > @@ -1969,7 +1992,10 @@ 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;
> >                       }
> > @@ -1984,7 +2010,7 @@ 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);
> >
> > @@ -4464,6 +4490,7 @@ static inline int l2cap_config_req(struct l2cap_conn *conn,
> >
> >  unlock:
> >       l2cap_chan_unlock(chan);
> > +     l2cap_chan_put(chan);
> >       return err;
> >  }
> >
> > @@ -4578,6 +4605,7 @@ static inline int l2cap_config_rsp(struct l2cap_conn *conn,
> >
> >  done:
> >       l2cap_chan_unlock(chan);
> > +     l2cap_chan_put(chan);
> >       return err;
> >  }
> >
> > @@ -5305,6 +5333,7 @@ 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;
> >  }
> > @@ -5397,6 +5426,7 @@ 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,
> > @@ -5426,6 +5456,7 @@ 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,
> > @@ -5489,6 +5520,7 @@ 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;
> >  }
> > @@ -5524,6 +5556,7 @@ static inline int l2cap_move_channel_confirm_rsp(struct l2cap_conn *conn,
> >       }
> >
> >       l2cap_chan_unlock(chan);
> > +     l2cap_chan_put(chan);
> >
> >       return 0;
> >  }
> > @@ -5896,12 +5929,11 @@ 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;
> > @@ -5912,7 +5944,9 @@ 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;
> >  }
> > @@ -7598,6 +7632,7 @@ 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,
> > @@ -8086,7 +8121,7 @@ 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;
> >       }
>
> --
> Lee Jones [李琼斯]
> Principal Technical Lead - Developer Services
> Linaro.org │ Open source software for Arm SoCs
> Follow Linaro: Facebook | Twitter | Blog
diff mbox series

Patch

diff --git a/include/net/bluetooth/l2cap.h b/include/net/bluetooth/l2cap.h
index 3c4f550e5a8b..2f766e3437ce 100644
--- a/include/net/bluetooth/l2cap.h
+++ b/include/net/bluetooth/l2cap.h
@@ -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)
diff --git a/net/bluetooth/l2cap_core.c b/net/bluetooth/l2cap_core.c
index 09ecaf556de5..77c0aac14539 100644
--- a/net/bluetooth/l2cap_core.c
+++ b/net/bluetooth/l2cap_core.c
@@ -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));
@@ -1969,7 +1992,10 @@  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;
 			}
@@ -1984,7 +2010,7 @@  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);
 
@@ -4464,6 +4490,7 @@  static inline int l2cap_config_req(struct l2cap_conn *conn,
 
 unlock:
 	l2cap_chan_unlock(chan);
+	l2cap_chan_put(chan);
 	return err;
 }
 
@@ -4578,6 +4605,7 @@  static inline int l2cap_config_rsp(struct l2cap_conn *conn,
 
 done:
 	l2cap_chan_unlock(chan);
+	l2cap_chan_put(chan);
 	return err;
 }
 
@@ -5305,6 +5333,7 @@  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;
 }
@@ -5397,6 +5426,7 @@  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,
@@ -5426,6 +5456,7 @@  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,
@@ -5489,6 +5520,7 @@  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;
 }
@@ -5524,6 +5556,7 @@  static inline int l2cap_move_channel_confirm_rsp(struct l2cap_conn *conn,
 	}
 
 	l2cap_chan_unlock(chan);
+	l2cap_chan_put(chan);
 
 	return 0;
 }
@@ -5896,12 +5929,11 @@  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;
@@ -5912,7 +5944,9 @@  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;
 }
@@ -7598,6 +7632,7 @@  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,
@@ -8086,7 +8121,7 @@  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;
 	}