From: Takashi Sakamoto <o-takashi@sakamocchi.jp>
To: Dan Carpenter <dan.carpenter@oracle.com>
Cc: kernel-janitors@vger.kernel.org, alsa-devel@alsa-project.org,
Clemens Ladisch <clemens@ladisch.de>,
Takashi Iwai <tiwai@suse.com>
Subject: Re: [PATCH] ALSA: bebob: potential info leak in hwdep_read()
Date: Wed, 07 Oct 2020 13:04:37 +0000 [thread overview]
Message-ID: <20201007130437.GA73459@workstation> (raw)
In-Reply-To: <20201007074928.GA2529578@mwanda>
Hi,
Thanks for the patch.
On Wed, Oct 07, 2020 at 10:49:28AM +0300, Dan Carpenter wrote:
> The "count" variable needs to be capped on every path so that we don't
> copy too much information to the user.
>
> Fixes: 618eabeae711 ("ALSA: bebob: Add hwdep interface")
> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
> ---
> sound/firewire/bebob/bebob_hwdep.c | 3 +--
> 1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/sound/firewire/bebob/bebob_hwdep.c b/sound/firewire/bebob/bebob_hwdep.c
> index 45b740f44c45..c362eb38ab90 100644
> --- a/sound/firewire/bebob/bebob_hwdep.c
> +++ b/sound/firewire/bebob/bebob_hwdep.c
> @@ -36,12 +36,11 @@ hwdep_read(struct snd_hwdep *hwdep, char __user *buf, long count,
> }
>
> memset(&event, 0, sizeof(event));
> + count = min_t(long, count, sizeof(event.lock_status));
> if (bebob->dev_lock_changed) {
> event.lock_status.type = SNDRV_FIREWIRE_EVENT_LOCK_STATUS;
> event.lock_status.status = (bebob->dev_lock_count > 0);
> bebob->dev_lock_changed = false;
> -
> - count = min_t(long, count, sizeof(event.lock_status));
> }
>
> spin_unlock_irq(&bebob->lock);
> --
> 2.28.0
Indeed, the bug can leak the contents of kernel memory into user space
unintentionally for the size indicated by ALSA HwDep application...
I will check the other drivers in ALSA firewire stack later for safe.
Thanks
Takashi Sakamoto
next prev parent reply other threads:[~2020-10-07 13:04 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-07 7:49 [PATCH] ALSA: bebob: potential info leak in hwdep_read() Dan Carpenter
2020-10-07 13:04 ` Takashi Sakamoto [this message]
2020-10-07 15:23 ` Takashi Sakamoto
2020-10-07 15:34 ` Takashi Iwai
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