Re: [PATCH v1] usb: typec: tcpm: Fix out-of-bounds read of the pds and pd_list arrays

[Heikki Krogerus <heikki.krogerus@linux.intel.com>]

On Tue, Oct 13, 2026 at 08:15:49AM +0000, Kyle Tso wrote:
> select_usb_power_delivery_show() iterates through port->pds (via the
> pd_get() callback) and tcpm_find_pd_data() iterates through
> port->pd_list until they find a NULL entry. However, tcpm_fw_get_caps()
> allocates only port->pd_count entries for each array, and
> tcpm_port_register_pd() fills all of them. Without a NULL terminator,
> both loops read and dereference one entry past the end:
> 
>   Unable to handle kernel paging request at virtual address
>   adacafaea9a8ac1a
>   Internal error: Oops: 0000000096000004 [#1] PREEMPT SMP
>   pc : select_usb_power_delivery_show+0xa4/0x110
>   lr : select_usb_power_delivery_show+0x90/0x110
>   Call trace:
>    select_usb_power_delivery_show+0xa4/0x110
>    dev_attr_show+0x38/0x74
>    sysfs_kf_seq_show+0xb4/0x130
>    kernfs_seq_show+0x44/0x54
>    seq_read_iter+0x158/0x4ec
>    kernfs_fop_read_iter+0x68/0x1bc
>    vfs_read+0x230/0x2c0
>    ksys_read+0x78/0xe8
>    __arm64_sys_read+0x1c/0x2c
>    invoke_syscall+0x58/0x118
>    el0_svc_common+0xb4/0xf4
>    do_el0_svc+0x24/0x80
>    el0_svc+0x2c/0x90
>    el0t_64_sync_handler+0x68/0xb4
>    el0t_64_sync+0x1a4/0x1a8
> 
> Allocate one extra, zeroed entry for both arrays so that they are
> always NULL-terminated.
> 
> Fixes: cd099cde4ed2 ("usb: typec: tcpm: Support multiple capabilities")
> Cc: stable@vger.kernel.org
> Reviewed-by: Badhri Jagan Sridharan <badhri@google.com>
> Signed-off-by: Kyle Tso <kyletso@google.com>

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

> ---
>  drivers/usb/typec/tcpm/tcpm.c | 11 +++++++++--
>  1 file changed, 9 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/usb/typec/tcpm/tcpm.c b/drivers/usb/typec/tcpm/tcpm.c
> index d721baef5210..8f4e10ec6d66 100644
> --- a/drivers/usb/typec/tcpm/tcpm.c
> +++ b/drivers/usb/typec/tcpm/tcpm.c
> @@ -8376,14 +8376,21 @@ static int tcpm_fw_get_caps(struct tcpm_port *port, struct fwnode_handle *fwnode
>  		}
>  	}
>  
> -	port->pds = devm_kcalloc(port->dev, port->pd_count, sizeof(struct usb_power_delivery *),
> +	/*
> +	 * Allocate one extra entry for each array to keep them NULL-terminated.
> +	 * select_usb_power_delivery_show() iterates through port->pds (via the
> +	 * pd_get callback) until it finds a NULL entry. Similarly,
> +	 * tcpm_find_pd_data() iterates through port->pd_list until it finds a
> +	 * NULL entry.
> +	 */
> +	port->pds = devm_kcalloc(port->dev, port->pd_count + 1, sizeof(struct usb_power_delivery *),
>  				 GFP_KERNEL);
>  	if (!port->pds) {
>  		ret = -ENOMEM;
>  		goto put_capabilities;
>  	}
>  
> -	port->pd_list = devm_kcalloc(port->dev, port->pd_count, sizeof(struct pd_data *),
> +	port->pd_list = devm_kcalloc(port->dev, port->pd_count + 1, sizeof(struct pd_data *),
>  				     GFP_KERNEL);
>  	if (!port->pd_list) {
>  		ret = -ENOMEM;
> -- 
> 2.56.0.385.gd3acb90ef8-goog

-- 
heikki