Re: [PATCH] usb: usbtmc: initialize memory written to device

[Greg KH <gregkh@linuxfoundation.org>]

On Fri, Oct 04, 2024 at 12:33:13PM +0000, Pimyn@web.codeaurora.org wrote:
> Avoid kernel-usb-infoleak by initializing all memory written to device.
> The buffer length uses 32bit alignment which might cause some buffer
> data to be read without any initialization.
> 
> Reported-by: syzbot+8f282cce71948071c335@syzkaller.appspotmail.com
> Closes: https://lore.kernel.org/all/0000000000006f6622061eb52dba@google.com/T/
> Signed-off-by: Pimyn Girgis <bemenboshra2001@gmail.com> (Google)
> ---
>  drivers/usb/class/usbtmc.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/usb/class/usbtmc.c b/drivers/usb/class/usbtmc.c
> index ffc9c6fdd7e1..d79a08dfb54d 100644
> --- a/drivers/usb/class/usbtmc.c
> +++ b/drivers/usb/class/usbtmc.c
> @@ -21,6 +21,7 @@
>  #include <linux/usb.h>
>  #include <linux/compat.h>
>  #include <linux/usb/tmc.h>
> +#include <linux/string.h>
>  
>  /* Increment API VERSION when changing tmc.h with new flags or ioctls
>   * or when changing a significant behavior of the driver.
> @@ -1169,6 +1170,8 @@ static ssize_t usbtmc_generic_write(struct usbtmc_file_data *file_data,
>  		 * (size + 3 & ~3) rounds up and simplifies user code
>  		 */
>  		aligned = (this_part + 3) & ~3;
> +		/* Initialize the remaining part of the buffer */
> +		memzero_explicit(buffer + this_part, aligned - this_part);

Why "explicit"?

Also, what about commit 625fa77151f0 ("USB: usbtmc: prevent
kernel-usb-infoleak"), doesn't that solve the issue here?

thanks,

greg k-h