linux-kernel - Re: [PATCH] HID: wacom: fix memory leak on size mismatch in wacom_wac_queue

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Message-ID: <CANRwn3RYdgHAc17QPBSNf44uhPp6kEH_GA58zs-Sg1LmE_aW+A@mail.gmail.com>
Date: Tue, 1 Apr 2025 08:21:20 -0700
From: Jason Gerecke <killertofu@...il.com>
To: Qasim Ijaz <qasdev00@...il.com>
Cc: ping.cheng@...om.com, jason.gerecke@...om.com, jikos@...nel.org, 
	bentiss@...nel.org, linux-input@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] HID: wacom: fix memory leak on size mismatch in wacom_wac_queue_flush()

On Fri, Mar 28, 2025 at 5:20 PM Qasim Ijaz <qasdev00@...il.com> wrote:
>
> In wacom_wac_queue_flush() the code allocates zero initialised
> buffer which it uses as a storage buffer for copying data from
> a fifo via kfifo_out(). The kfifo_out() function returns the
> number of elements it has copied. The code checks if the number
> of copied elements does not equal the size of the fifo record,
> if it does not it simply skips the entry and continues to the
> next iteration. However it does not release the storage buffer
> leading to a memory leak.
>
> Fix the memory leak by freeing the buffer on size mismatch.
>
> Fixes: 5e013ad20689 ("HID: wacom: Remove static WACOM_PKGLEN_MAX limit")
> Signed-off-by: Qasim Ijaz <qasdev00@...il.com>
> ---
>  drivers/hid/wacom_sys.c | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/drivers/hid/wacom_sys.c b/drivers/hid/wacom_sys.c
> index 666b7eb0fdfe..3e4f823f8ee8 100644
> --- a/drivers/hid/wacom_sys.c
> +++ b/drivers/hid/wacom_sys.c
> @@ -87,6 +87,7 @@ static void wacom_wac_queue_flush(struct hid_device *hdev,
>                         // to flush seems reasonable enough, however.
>                         hid_warn(hdev, "%s: removed fifo entry with unexpected size\n",
>                                  __func__);
> +                       kfree(buf);
>                         continue;
>                 }
>                 err = hid_report_raw_event(hdev, HID_INPUT_REPORT, buf, size, false);
> --
> 2.39.5
>

Patch looks good to me. With or without Markus' comments addressed,

Reviewed-by: Jason Gerecke <jason.gerecke@...om.com>

Jason (she/they)
---
Now instead of four in the eights place /
you’ve got three, ‘Cause you added one  /
(That is to say, eight) to the two,     /
But you can’t take seven from three,    /
So you look at the sixty-fours....