From: Benson Leung <bleung@google.com>
To: Jameson Thies <jthies@google.com>
Cc: heikki.krogerus@linux.intel.com, linux-usb@vger.kernel.org,
linux-kernel@vger.kernel.org, bleung@chromium.org,
gregkh@linuxfoundation.org, akuchynski@chromium.org,
stable@vger.kernel.org
Subject: Re: [PATCH v2] usb: typec: ucsi: displayport: Fix OOB altmode array index
Date: Sat, 5 Sep 2026 00:53:09 +0000 [thread overview]
Message-ID: <aptn9eUDt6Q63gWF@google.com> (raw)
In-Reply-To: <20260904234401.2339633-1-jthies@google.com>
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On Fri, Sep 04, 2026 at 11:44:01PM +0000, Jameson Thies wrote:
> The UCSI displayport driver indexes the connector's port altmode array
> with the GET_CURRENT_CAM response after checking it is not 0xff. The
> port altmode array is UCSI_MAX_ALTMODES elements long. If the PPM
> returns an invalid GET_CURRENT_CAM response above UCSI_MAX_ALTMODES and
> not equal to 0xff, the kernel may crash with an array index OOB error.
>
> Update the UCSI displayport driver to verify the current cam is less
> than UCSI_MAX_ALTMODES before accessing the port altmode array.
>
> Fixes: af8622f6a585 ("usb: typec: ucsi: Support for DisplayPort alt mode")
> Cc: stable@vger.kernel.org
> Signed-off-by: Jameson Thies <jthies@google.com>
Reviewed-by: Benson Leung <bleung@chromium.org>
> ---
> Changes in v2:
> - removed 0xff alt mode assignement when GET_CURRENT_CAM returns an error.
> - return -EINVAL when alt mode index above UCSI_MAX_ALTMODES is returned.
>
> drivers/usb/typec/ucsi/displayport.c | 7 +++++--
> 1 file changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/usb/typec/ucsi/displayport.c b/drivers/usb/typec/ucsi/displayport.c
> index 7067f2561b84..572da7bbd29c 100644
> --- a/drivers/usb/typec/ucsi/displayport.c
> +++ b/drivers/usb/typec/ucsi/displayport.c
> @@ -71,11 +71,14 @@ static int ucsi_displayport_enter(struct typec_altmode *alt, u32 *vdo)
> if (ret < 0) {
> if (ucsi->version > 0x0100)
> goto err_unlock;
> - cur = 0xff;
> }
>
> if (cur != 0xff) {
> - ret = dp->con->port_altmode[cur] == alt ? 0 : -EBUSY;
> + if (cur < UCSI_MAX_ALTMODES)
> + ret = dp->con->port_altmode[cur] == alt ? 0 : -EBUSY;
> + else
> + ret = -EINVAL;
> +
> goto err_unlock;
> }
>
>
> base-commit: cee9395acd8043be0644b25c34bfa86623f2b935
> --
> 2.55.0.979.g7e5102b832-goog
>
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prev parent reply other threads:[~2026-09-05 0:53 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-04 23:44 Jameson Thies
2026-09-05 0:53 ` Benson Leung [this message]
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