linux-kernel - Re: [PATCH] HID: wacom: handle kzalloc() allocation failure in wacom_wac_queue

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Message-ID: <CANRwn3THBtd=e46a1Gaa0CFqJ-dwkLjyqPqpJU4kMjpDUX-n2g@mail.gmail.com>
Date: Tue, 1 Apr 2025 08:21:14 -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: handle kzalloc() allocation failure in wacom_wac_queue_flush()

On Fri, Mar 28, 2025 at 5:20 PM Qasim Ijaz <qasdev00@...il.com> wrote:
>
> During wacom_wac_queue_flush() the code calls
> kzalloc() to allocate a zero initialised buffer
> which it uses as a storage buffer to get data
> from the fifo via kfifo_out(). However it does not
> check kzalloc() for allocation failure which returns
> NULL and could potentially lead to a NULL deref.
>
> Fix this by checking for kzalloc() failure and skipping
> the current entry if allocation failure occurs.
>
> Fixes: 5e013ad20689 ("HID: wacom: Remove static WACOM_PKGLEN_MAX limit")
> Signed-off-by: Qasim Ijaz <qasdev00@...il.com>
> ---
>  drivers/hid/wacom_sys.c | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/hid/wacom_sys.c b/drivers/hid/wacom_sys.c
> index 97393a3083ca..666b7eb0fdfe 100644
> --- a/drivers/hid/wacom_sys.c
> +++ b/drivers/hid/wacom_sys.c
> @@ -70,10 +70,16 @@ static void wacom_wac_queue_flush(struct hid_device *hdev,
>  {
>         while (!kfifo_is_empty(fifo)) {
>                 int size = kfifo_peek_len(fifo);
> -               u8 *buf = kzalloc(size, GFP_KERNEL);
> +               u8 *buf;
>                 unsigned int count;
>                 int err;
>
> +               buf = kzalloc(size, GFP_KERNEL);
> +               if (!buf) {
> +                       kfifo_skip(fifo);
> +                       continue;
> +               }
> +
>                 count = kfifo_out(fifo, buf, size);
>                 if (count != size) {
>                         // Hard to say what is the "right" action in this
> --
> 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....