[PATCH] usb: typec: altmode: Fix typec_altmode_get_partner sometimes returning an invalid pointer

[PATCH] usb: typec: altmode: Fix typec_altmode_get_partner sometimes returning an invalid pointer

[Hans de Goede]

From: Naoki Kiryu <naonaokiryu2@gmail.com>

Before this commit, typec_altmode_get_partner would return a
const struct typec_altmode * pointing to address 0x08 when
to_altmode(adev)->partner was NULL.

Add a check for to_altmode(adev)->partner being NULL to fix this.

BugLink: https://bugzilla.kernel.org/show_bug.cgi?id=206365
BugLink: https://bugzilla.redhat.com/show_bug.cgi?id=1785972
Fixes: 5f54a85db5df ("usb: typec: Make sure an alt mode exist before getting its partner")
Cc: stable@vger.kernel.org
Signed-off-by: Naoki Kiryu <naonaokiryu2@gmail.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
---
 drivers/usb/typec/bus.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/typec/bus.c b/drivers/usb/typec/bus.c
index c823122f9cb7..e8ddb81cb6df 100644
--- a/drivers/usb/typec/bus.c
+++ b/drivers/usb/typec/bus.c
@@ -198,7 +198,10 @@ EXPORT_SYMBOL_GPL(typec_altmode_vdm);
 const struct typec_altmode *
 typec_altmode_get_partner(struct typec_altmode *adev)
 {
-	return adev ? &to_altmode(adev)->partner->adev : NULL;
+	if (!adev || !to_altmode(adev)->partner)
+		return NULL;
+
+	return &to_altmode(adev)->partner->adev;
 }
 EXPORT_SYMBOL_GPL(typec_altmode_get_partner);
 
-- 
2.26.0

Re: [PATCH] usb: typec: altmode: Fix typec_altmode_get_partner sometimes returning an invalid pointer

[Heikki Krogerus]

On Wed, Apr 22, 2020 at 04:43:45PM +0200, Hans de Goede wrote:
> From: Naoki Kiryu <naonaokiryu2@gmail.com>
> 
> Before this commit, typec_altmode_get_partner would return a
> const struct typec_altmode * pointing to address 0x08 when
> to_altmode(adev)->partner was NULL.
> 
> Add a check for to_altmode(adev)->partner being NULL to fix this.
> 
> BugLink: https://bugzilla.kernel.org/show_bug.cgi?id=206365
> BugLink: https://bugzilla.redhat.com/show_bug.cgi?id=1785972
> Fixes: 5f54a85db5df ("usb: typec: Make sure an alt mode exist before getting its partner")
> Cc: stable@vger.kernel.org
> Signed-off-by: Naoki Kiryu <naonaokiryu2@gmail.com>
> Signed-off-by: Hans de Goede <hdegoede@redhat.com>

Acked-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>

> ---
>  drivers/usb/typec/bus.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/usb/typec/bus.c b/drivers/usb/typec/bus.c
> index c823122f9cb7..e8ddb81cb6df 100644
> --- a/drivers/usb/typec/bus.c
> +++ b/drivers/usb/typec/bus.c
> @@ -198,7 +198,10 @@ EXPORT_SYMBOL_GPL(typec_altmode_vdm);
>  const struct typec_altmode *
>  typec_altmode_get_partner(struct typec_altmode *adev)
>  {
> -	return adev ? &to_altmode(adev)->partner->adev : NULL;
> +	if (!adev || !to_altmode(adev)->partner)
> +		return NULL;
> +
> +	return &to_altmode(adev)->partner->adev;
>  }
>  EXPORT_SYMBOL_GPL(typec_altmode_get_partner);
>  
> -- 
> 2.26.0

thanks,

-- 
heikki