[PATCH] hso: fix refcnt leak in recent patch.

[PATCH] hso: fix refcnt leak in recent patch.

[NeilBrown]

[-- Attachment #1: Type: text/plain, Size: 1107 bytes --]



Prior to
commit 29bd3bc1194c624ce863cab2a7da9bc1f0c3b47b
    hso: fix crash when device disappears while serial port is open

hso_serial_open would always kref_get(&serial->parent->ref) before
returning zero.
Since that commit, it only calls kref_get when returning 0 if
serial->port.count was zero.

This results in calls to
       kref_put(&serial->parent->ref, hso_serial_ref_free);

after hso_serial_ref_free has been called, which dereferences a freed
pointer.

This patch adds the missing kref_get().

Fixes: commit 29bd3bc1194c624ce863cab2a7da9bc1f0c3b47b
Cc: stable@vger.kernel.org (v4.0)
Cc: Olivier Sobrie <olivier@sobrie.be>
Signed-off-by: NeilBrown <neilb@suse.de>

diff --git a/drivers/net/usb/hso.c b/drivers/net/usb/hso.c
index 75befc1bd816..6848fc903340 100644
--- a/drivers/net/usb/hso.c
+++ b/drivers/net/usb/hso.c
@@ -1299,6 +1299,7 @@ static int hso_serial_open(struct tty_struct *tty, struct file *filp)
 		}
 	} else {
 		D1("Port was already open");
+		kref_get(&serial->parent->ref);
 	}
 
 	usb_autopm_put_interface(serial->parent->interface);

[-- Attachment #2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 811 bytes --]

Re: [PATCH] hso: fix refcnt leak in recent patch.

[NeilBrown]

[-- Attachment #1: Type: text/plain, Size: 3379 bytes --]

On Tue, 14 Apr 2015 09:36:34 +1000 NeilBrown <neilb-l3A5Bk7waGM@public.gmane.org> wrote:

> 
> 
> Prior to
> commit 29bd3bc1194c624ce863cab2a7da9bc1f0c3b47b
>     hso: fix crash when device disappears while serial port is open
> 
> hso_serial_open would always kref_get(&serial->parent->ref) before
> returning zero.
> Since that commit, it only calls kref_get when returning 0 if
> serial->port.count was zero.
> 
> This results in calls to
>        kref_put(&serial->parent->ref, hso_serial_ref_free);
> 
> after hso_serial_ref_free has been called, which dereferences a freed
> pointer.
> 
> This patch adds the missing kref_get().
> 
> Fixes: commit 29bd3bc1194c624ce863cab2a7da9bc1f0c3b47b
> Cc: stable-u79uwXL29TY76Z2rM5mHXA@public.gmane.org (v4.0)
> Cc: Olivier Sobrie <olivier-Ui3EtX6WB9GzQB+pC5nmwQ@public.gmane.org>
> Signed-off-by: NeilBrown <neilb-l3A5Bk7waGM@public.gmane.org>
> 
> diff --git a/drivers/net/usb/hso.c b/drivers/net/usb/hso.c
> index 75befc1bd816..6848fc903340 100644
> --- a/drivers/net/usb/hso.c
> +++ b/drivers/net/usb/hso.c
> @@ -1299,6 +1299,7 @@ static int hso_serial_open(struct tty_struct *tty, struct file *filp)
>  		}
>  	} else {
>  		D1("Port was already open");
> +		kref_get(&serial->parent->ref);
>  	}
>  
>  	usb_autopm_put_interface(serial->parent->interface);


Sorry - that was wrong.
I'm getting crashes which strongly suggest the kref_put is being called extra
times, but I misunderstood the code and was hasty.

Maybe this instead?

Thanks,
NeilBrown

From: NeilBrown <neil-+NVA1uvv1dVBDLzU/O5InQ@public.gmane.org>
Date: Tue, 14 Apr 2015 09:33:03 +1000
Subject: [PATCH] hso: fix refcnt leak in recent patch.

Prior to
commit 29bd3bc1194c624ce863cab2a7da9bc1f0c3b47b
    hso: fix crash when device disappears while serial port is open

a kref_get on serial->parent->ref would be taken on each open,
and it would be kref_put on each close.

Now the kref_put happens when the tty_struct is finally put (via
the 'cleanup') providing tty->driver_data has been set.
So the kref_get must be called exact once when tty->driver_data is
set.

With the current code, if the first open fails the kref_get() is never
called, but the kref_put() is called, leaving to a crash.

So change the kref_get call to happen exactly when ->driver_data is
changed from NULL to non-NULL.

Fixes: commit 29bd3bc1194c624ce863cab2a7da9bc1f0c3b47b
Cc: stable-u79uwXL29TY76Z2rM5mHXA@public.gmane.org (v4.0)
Cc: Olivier Sobrie <olivier-Ui3EtX6WB9GzQB+pC5nmwQ@public.gmane.org>
Signed-off-by: NeilBrown <neil-+NVA1uvv1dVBDLzU/O5InQ@public.gmane.org>

diff --git a/drivers/net/usb/hso.c b/drivers/net/usb/hso.c
index 75befc1bd816..17fd3820263a 100644
--- a/drivers/net/usb/hso.c
+++ b/drivers/net/usb/hso.c
@@ -1278,6 +1278,8 @@ static int hso_serial_open(struct tty_struct *tty, struct file *filp)
 	D1("Opening %d", serial->minor);
 
 	/* setup */
+	if (tty->driver_data == NULL)
+		kref_get(&serial->parent->ref);
 	tty->driver_data = serial;
 	tty_port_tty_set(&serial->port, tty);
 
@@ -1294,8 +1296,6 @@ static int hso_serial_open(struct tty_struct *tty, struct file *filp)
 		if (result) {
 			hso_stop_serial_device(serial->parent);
 			serial->port.count--;
-		} else {
-			kref_get(&serial->parent->ref);
 		}
 	} else {
 		D1("Port was already open");

[-- Attachment #2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 811 bytes --]

Re: [PATCH] hso: fix refcnt leak in recent patch.

[Olivier Sobrie]

Hello Neil,

On Tue, Apr 14, 2015 at 11:03:03AM +1000, NeilBrown wrote:
> On Tue, 14 Apr 2015 09:36:34 +1000 NeilBrown <neilb-l3A5Bk7waGM@public.gmane.org> wrote:
> 
> > 
> > 
> > Prior to
> > commit 29bd3bc1194c624ce863cab2a7da9bc1f0c3b47b
> >     hso: fix crash when device disappears while serial port is open
> > 
> > hso_serial_open would always kref_get(&serial->parent->ref) before
> > returning zero.
> > Since that commit, it only calls kref_get when returning 0 if
> > serial->port.count was zero.
> > 
> > This results in calls to
> >        kref_put(&serial->parent->ref, hso_serial_ref_free);
> > 
> > after hso_serial_ref_free has been called, which dereferences a freed
> > pointer.
> > 
> > This patch adds the missing kref_get().
> > 
> > Fixes: commit 29bd3bc1194c624ce863cab2a7da9bc1f0c3b47b
> > Cc: stable-u79uwXL29TY76Z2rM5mHXA@public.gmane.org (v4.0)
> > Cc: Olivier Sobrie <olivier-Ui3EtX6WB9GzQB+pC5nmwQ@public.gmane.org>
> > Signed-off-by: NeilBrown <neilb-l3A5Bk7waGM@public.gmane.org>
> > 
> > diff --git a/drivers/net/usb/hso.c b/drivers/net/usb/hso.c
> > index 75befc1bd816..6848fc903340 100644
> > --- a/drivers/net/usb/hso.c
> > +++ b/drivers/net/usb/hso.c
> > @@ -1299,6 +1299,7 @@ static int hso_serial_open(struct tty_struct *tty, struct file *filp)
> >  		}
> >  	} else {
> >  		D1("Port was already open");
> > +		kref_get(&serial->parent->ref);
> >  	}
> >  
> >  	usb_autopm_put_interface(serial->parent->interface);
> 
> 
> Sorry - that was wrong.
> I'm getting crashes which strongly suggest the kref_put is being called extra
> times, but I misunderstood the code and was hasty.
> 
> Maybe this instead?

Indeed, if I undestand correctly the code in tty_io.c, cleanup() method
is also called when the open fails while kref_get is only done if the
open succeeds. Sorry for that mess.
I assume you get that crash when hso_start_serial_device() returns
an error?

At first sight, the patch below looks good to me.
I'll test it in the next days.

Thank you,

Olivier

> 
> Thanks,
> NeilBrown
> 
> From: NeilBrown <neil-+NVA1uvv1dVBDLzU/O5InQ@public.gmane.org>
> Date: Tue, 14 Apr 2015 09:33:03 +1000
> Subject: [PATCH] hso: fix refcnt leak in recent patch.
> 
> Prior to
> commit 29bd3bc1194c624ce863cab2a7da9bc1f0c3b47b
>     hso: fix crash when device disappears while serial port is open
> 
> a kref_get on serial->parent->ref would be taken on each open,
> and it would be kref_put on each close.
> 
> Now the kref_put happens when the tty_struct is finally put (via
> the 'cleanup') providing tty->driver_data has been set.
> So the kref_get must be called exact once when tty->driver_data is
> set.
> 
> With the current code, if the first open fails the kref_get() is never
> called, but the kref_put() is called, leaving to a crash.
> 
> So change the kref_get call to happen exactly when ->driver_data is
> changed from NULL to non-NULL.
> 
> Fixes: commit 29bd3bc1194c624ce863cab2a7da9bc1f0c3b47b
> Cc: stable-u79uwXL29TY76Z2rM5mHXA@public.gmane.org (v4.0)
> Cc: Olivier Sobrie <olivier-Ui3EtX6WB9GzQB+pC5nmwQ@public.gmane.org>
> Signed-off-by: NeilBrown <neil-+NVA1uvv1dVBDLzU/O5InQ@public.gmane.org>
> 
> diff --git a/drivers/net/usb/hso.c b/drivers/net/usb/hso.c
> index 75befc1bd816..17fd3820263a 100644
> --- a/drivers/net/usb/hso.c
> +++ b/drivers/net/usb/hso.c
> @@ -1278,6 +1278,8 @@ static int hso_serial_open(struct tty_struct *tty, struct file *filp)
>  	D1("Opening %d", serial->minor);
>  
>  	/* setup */
> +	if (tty->driver_data == NULL)
> +		kref_get(&serial->parent->ref);
>  	tty->driver_data = serial;
>  	tty_port_tty_set(&serial->port, tty);
>  
> @@ -1294,8 +1296,6 @@ static int hso_serial_open(struct tty_struct *tty, struct file *filp)
>  		if (result) {
>  			hso_stop_serial_device(serial->parent);
>  			serial->port.count--;
> -		} else {
> -			kref_get(&serial->parent->ref);
>  		}
>  	} else {
>  		D1("Port was already open");



--
To unsubscribe from this list: send the line "unsubscribe linux-usb" in
the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html

Re: [PATCH] hso: fix refcnt leak in recent patch.

[NeilBrown]

[-- Attachment #1: Type: text/plain, Size: 4452 bytes --]

On Tue, 14 Apr 2015 08:50:01 +0200 Olivier Sobrie <olivier@sobrie.be> wrote:

> Hello Neil,
> 
> On Tue, Apr 14, 2015 at 11:03:03AM +1000, NeilBrown wrote:
> > On Tue, 14 Apr 2015 09:36:34 +1000 NeilBrown <neilb@suse.de> wrote:
> > 
> > > 
> > > 
> > > Prior to
> > > commit 29bd3bc1194c624ce863cab2a7da9bc1f0c3b47b
> > >     hso: fix crash when device disappears while serial port is open
> > > 
> > > hso_serial_open would always kref_get(&serial->parent->ref) before
> > > returning zero.
> > > Since that commit, it only calls kref_get when returning 0 if
> > > serial->port.count was zero.
> > > 
> > > This results in calls to
> > >        kref_put(&serial->parent->ref, hso_serial_ref_free);
> > > 
> > > after hso_serial_ref_free has been called, which dereferences a freed
> > > pointer.
> > > 
> > > This patch adds the missing kref_get().
> > > 
> > > Fixes: commit 29bd3bc1194c624ce863cab2a7da9bc1f0c3b47b
> > > Cc: stable@vger.kernel.org (v4.0)
> > > Cc: Olivier Sobrie <olivier@sobrie.be>
> > > Signed-off-by: NeilBrown <neilb@suse.de>
> > > 
> > > diff --git a/drivers/net/usb/hso.c b/drivers/net/usb/hso.c
> > > index 75befc1bd816..6848fc903340 100644
> > > --- a/drivers/net/usb/hso.c
> > > +++ b/drivers/net/usb/hso.c
> > > @@ -1299,6 +1299,7 @@ static int hso_serial_open(struct tty_struct *tty, struct file *filp)
> > >  		}
> > >  	} else {
> > >  		D1("Port was already open");
> > > +		kref_get(&serial->parent->ref);
> > >  	}
> > >  
> > >  	usb_autopm_put_interface(serial->parent->interface);
> > 
> > 
> > Sorry - that was wrong.
> > I'm getting crashes which strongly suggest the kref_put is being called extra
> > times, but I misunderstood the code and was hasty.
> > 
> > Maybe this instead?
> 
> Indeed, if I undestand correctly the code in tty_io.c, cleanup() method
> is also called when the open fails while kref_get is only done if the
> open succeeds. Sorry for that mess.
> I assume you get that crash when hso_start_serial_device() returns
> an error?

Yes, that's correct.

> 
> At first sight, the patch below looks good to me.
> I'll test it in the next days.

Thanks.

NeilBrown

> 
> Thank you,
> 
> Olivier
> 
> > 
> > Thanks,
> > NeilBrown
> > 
> > From: NeilBrown <neil@brown.name>
> > Date: Tue, 14 Apr 2015 09:33:03 +1000
> > Subject: [PATCH] hso: fix refcnt leak in recent patch.
> > 
> > Prior to
> > commit 29bd3bc1194c624ce863cab2a7da9bc1f0c3b47b
> >     hso: fix crash when device disappears while serial port is open
> > 
> > a kref_get on serial->parent->ref would be taken on each open,
> > and it would be kref_put on each close.
> > 
> > Now the kref_put happens when the tty_struct is finally put (via
> > the 'cleanup') providing tty->driver_data has been set.
> > So the kref_get must be called exact once when tty->driver_data is
> > set.
> > 
> > With the current code, if the first open fails the kref_get() is never
> > called, but the kref_put() is called, leaving to a crash.
> > 
> > So change the kref_get call to happen exactly when ->driver_data is
> > changed from NULL to non-NULL.
> > 
> > Fixes: commit 29bd3bc1194c624ce863cab2a7da9bc1f0c3b47b
> > Cc: stable@vger.kernel.org (v4.0)
> > Cc: Olivier Sobrie <olivier@sobrie.be>
> > Signed-off-by: NeilBrown <neil@brown.name>
> > 
> > diff --git a/drivers/net/usb/hso.c b/drivers/net/usb/hso.c
> > index 75befc1bd816..17fd3820263a 100644
> > --- a/drivers/net/usb/hso.c
> > +++ b/drivers/net/usb/hso.c
> > @@ -1278,6 +1278,8 @@ static int hso_serial_open(struct tty_struct *tty, struct file *filp)
> >  	D1("Opening %d", serial->minor);
> >  
> >  	/* setup */
> > +	if (tty->driver_data == NULL)
> > +		kref_get(&serial->parent->ref);
> >  	tty->driver_data = serial;
> >  	tty_port_tty_set(&serial->port, tty);
> >  
> > @@ -1294,8 +1296,6 @@ static int hso_serial_open(struct tty_struct *tty, struct file *filp)
> >  		if (result) {
> >  			hso_stop_serial_device(serial->parent);
> >  			serial->port.count--;
> > -		} else {
> > -			kref_get(&serial->parent->ref);
> >  		}
> >  	} else {
> >  		D1("Port was already open");
> 
> 
> 
> --
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at  http://www.tux.org/lkml/


[-- Attachment #2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 811 bytes --]

Re: [PATCH] hso: fix refcnt leak in recent patch.

[Olivier Sobrie]

On Tue, Apr 14, 2015 at 11:03:03AM +1000, NeilBrown wrote:
> On Tue, 14 Apr 2015 09:36:34 +1000 NeilBrown <neilb@suse.de> wrote:
> 
> > 
> > 
> > Prior to
> > commit 29bd3bc1194c624ce863cab2a7da9bc1f0c3b47b
> >     hso: fix crash when device disappears while serial port is open
> > 
> > hso_serial_open would always kref_get(&serial->parent->ref) before
> > returning zero.
> > Since that commit, it only calls kref_get when returning 0 if
> > serial->port.count was zero.
> > 
> > This results in calls to
> >        kref_put(&serial->parent->ref, hso_serial_ref_free);
> > 
> > after hso_serial_ref_free has been called, which dereferences a freed
> > pointer.
> > 
> > This patch adds the missing kref_get().
> > 
> > Fixes: commit 29bd3bc1194c624ce863cab2a7da9bc1f0c3b47b
> > Cc: stable@vger.kernel.org (v4.0)
> > Cc: Olivier Sobrie <olivier@sobrie.be>
> > Signed-off-by: NeilBrown <neilb@suse.de>
> > 
> > diff --git a/drivers/net/usb/hso.c b/drivers/net/usb/hso.c
> > index 75befc1bd816..6848fc903340 100644
> > --- a/drivers/net/usb/hso.c
> > +++ b/drivers/net/usb/hso.c
> > @@ -1299,6 +1299,7 @@ static int hso_serial_open(struct tty_struct *tty, struct file *filp)
> >  		}
> >  	} else {
> >  		D1("Port was already open");
> > +		kref_get(&serial->parent->ref);
> >  	}
> >  
> >  	usb_autopm_put_interface(serial->parent->interface);
> 
> 
> Sorry - that was wrong.
> I'm getting crashes which strongly suggest the kref_put is being called extra
> times, but I misunderstood the code and was hasty.
> 
> Maybe this instead?

I tested the patch and it looks fine :-)
Thank you,
Olivier

> 
> Thanks,
> NeilBrown
> 
> From: NeilBrown <neil@brown.name>
> Date: Tue, 14 Apr 2015 09:33:03 +1000
> Subject: [PATCH] hso: fix refcnt leak in recent patch.
> 
> Prior to
> commit 29bd3bc1194c624ce863cab2a7da9bc1f0c3b47b
>     hso: fix crash when device disappears while serial port is open
> 
> a kref_get on serial->parent->ref would be taken on each open,
> and it would be kref_put on each close.
> 
> Now the kref_put happens when the tty_struct is finally put (via
> the 'cleanup') providing tty->driver_data has been set.
> So the kref_get must be called exact once when tty->driver_data is
> set.
> 
> With the current code, if the first open fails the kref_get() is never
> called, but the kref_put() is called, leaving to a crash.
> 
> So change the kref_get call to happen exactly when ->driver_data is
> changed from NULL to non-NULL.
> 
> Fixes: commit 29bd3bc1194c624ce863cab2a7da9bc1f0c3b47b
> Cc: stable@vger.kernel.org (v4.0)
> Cc: Olivier Sobrie <olivier@sobrie.be>

Tested-by: Olivier Sobrie <olivier@sobrie.be>

> Signed-off-by: NeilBrown <neil@brown.name>
> 
> diff --git a/drivers/net/usb/hso.c b/drivers/net/usb/hso.c
> index 75befc1bd816..17fd3820263a 100644
> --- a/drivers/net/usb/hso.c
> +++ b/drivers/net/usb/hso.c
> @@ -1278,6 +1278,8 @@ static int hso_serial_open(struct tty_struct *tty, struct file *filp)
>  	D1("Opening %d", serial->minor);
>  
>  	/* setup */
> +	if (tty->driver_data == NULL)
> +		kref_get(&serial->parent->ref);
>  	tty->driver_data = serial;
>  	tty_port_tty_set(&serial->port, tty);
>  
> @@ -1294,8 +1296,6 @@ static int hso_serial_open(struct tty_struct *tty, struct file *filp)
>  		if (result) {
>  			hso_stop_serial_device(serial->parent);
>  			serial->port.count--;
> -		} else {
> -			kref_get(&serial->parent->ref);
>  		}
>  	} else {
>  		D1("Port was already open");



-- 
Olivier