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@gmail.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

On Sat, 29 Mar 2025, Qasim Ijaz 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@gmail.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

Applied, thanks.

-- 
Jiri Kosina
SUSE Labs

On Fri, Mar 28, 2025 at 5:20 PM Qasim Ijaz <qasdev00@gmail.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@gmail.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@wacom.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....

…
> 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.
…
                                            pointer dereference?

I imagine that word wrapping can occasionally become a bit nicer
for text lines which may be longer than 52 characters.

Regards,
Markus