Re: [Linux-kernel-mentees] [PATCH] firewire: Prevent kernel-infoleak in ioctl_get_info()

[Arnd Bergmann]

On Mon, Jul 27, 2020 at 5:18 PM Peilin Ye <yepeilin.cs@xxxxxxxxx> wrote:
>
> ioctl_get_info() is copying uninitialized stack memory to userspace due to
> the compiler not initializing holes in statically allocated structures.
> Fix it by initializing `event` using memset() in fill_bus_reset_event().
>
> Cc: stable@xxxxxxxxxxxxxxx
> Suggested-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
> Suggested-by: Arnd Bergmann <arnd@xxxxxxxx>
> Signed-off-by: Peilin Ye <yepeilin.cs@xxxxxxxxx>

Acked-by: Arnd Bergmann <arnd@xxxxxxxx>

I would recommend always looking through the git history of the
file to come up with an appropriate 'Fixes' tag. In this case

$ git log -p --follow drivers/firewire/core-cdev.c

searching for any mention of fill_bus_reset_event leads you to
commit 344bbc4de14e.

In my ~/.gitconfig I have this alias:

[core]
        abbrev = 12
[alias]
        fixes = show --format='Fixes: %h (\"%s\")' -s

With something like that, calling 'git fixes 344bbc4de14e' produces
the line to copy:

Fixes: 344bbc4de14e ("firewire: Generalize get_config_rom to get_info.")

     Arnd

> ---
>  drivers/firewire/core-cdev.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/drivers/firewire/core-cdev.c b/drivers/firewire/core-cdev.c
> index fb6c651214f3..2341d762df5b 100644
> --- a/drivers/firewire/core-cdev.c
> +++ b/drivers/firewire/core-cdev.c
> @@ -340,6 +340,8 @@ static void fill_bus_reset_event(struct fw_cdev_event_bus_reset *event,
>  {
>         struct fw_card *card = client->device->card;
>
> +       memset(event, 0, sizeof(*event));
> +
>         spin_lock_irq(&card->lock);
>
>         event->closure       = client->bus_reset_closure;
> --
> 2.25.1
>