Re: [PATCH] Bluetooth: HIDP: fix missing length checks in hidp_input_report()

[Greg KH]

On Sun, May 17, 2026 at 07:48:05PM -0400, Muhammad Bilal wrote:
> hidp_input_report() reads keyboard and mouse payload data from an skb
> without first verifying that skb->len contains enough data.
> 
> hidp_recv_intr_frame() pulls the 1-byte HIDP header before dispatching
> to hidp_input_report(). If a paired device sends a truncated packet,
> the handler reads beyond the valid skb data, resulting in
> an out-of-bounds read of skb data.
> The OOB bytes may be interpreted as phantom key presses or
> spurious mouse movement.
> 
> Add a check that skb->len is non-zero before the type switch, and
> per-report-type minimum length checks before accessing the payload.
> 
> Signed-off-by: Muhammad Bilal <meatuni001@xxxxxxxxx>
> ---
>  net/bluetooth/hidp/core.c | 19 ++++++++++++++++---
>  1 file changed, 16 insertions(+), 3 deletions(-)
> 
> diff --git a/net/bluetooth/hidp/core.c b/net/bluetooth/hidp/core.c
> index 976f91eeb..03838a6ff 100644
> --- a/net/bluetooth/hidp/core.c
> +++ b/net/bluetooth/hidp/core.c
> @@ -179,12 +179,22 @@ static void hidp_input_report(struct hidp_session *session, struct sk_buff *skb)
>  {
>  	struct input_dev *dev = session->input;
>  	unsigned char *keys = session->keys;
> -	unsigned char *udata = skb->data + 1;
> -	signed char *sdata = skb->data + 1;
> -	int i, size = skb->len - 1;
> +	unsigned char *udata;
> +	signed char *sdata;
> +	int i, size;
> +
> +	if (!skb->len)
> +		return;
> +
> +	udata = skb->data + 1;
> +	sdata = skb->data + 1;
> +	size = skb->len - 1;
>  
>  	switch (skb->data[0]) {
>  	case 0x01:	/* Keyboard report */
> +		if (size < 8)
> +			break;
> +
>  		for (i = 0; i < 8; i++)
>  			input_report_key(dev, hidp_keycode[i + 224], (udata[0] >> i) & 1);
>  
> @@ -213,6 +223,9 @@ static void hidp_input_report(struct hidp_session *session, struct sk_buff *skb)
>  		break;
>  
>  	case 0x02:	/* Mouse report */
> +		if (size < 3)
> +			break;
> +
>  		input_report_key(dev, BTN_LEFT,   sdata[0] & 0x01);
>  		input_report_key(dev, BTN_RIGHT,  sdata[0] & 0x02);
>  		input_report_key(dev, BTN_MIDDLE, sdata[0] & 0x04);
> -- 
> 2.54.0
> 
> 

<formletter>

This is not the correct way to submit patches for inclusion in the
stable kernel tree.  Please read:
    https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html
for how to do this properly.

</formletter>