Alsa-Devel Archive on lore.kernel.org
 help / color / Atom feed
From: Takashi Iwai <tiwai@suse.de>
To: alsa-devel@alsa-project.org
Subject: [PATCH 2/2] ALSA: pcm: oss: Fix potential out-of-bounds shift
Date: Wed,  9 Dec 2020 09:45:52 +0100
Message-ID: <20201209084552.17109-2-tiwai@suse.de> (raw)
In-Reply-To: <20201209084552.17109-1-tiwai@suse.de>

syzbot spotted a potential out-of-bounds shift in the PCM OSS layer
where it calculates the buffer size with the arbitrary shift value
given via an ioctl.

Add a range check for avoiding the undefined behavior.
As the value can be treated by a signed integer, the max shift should
be 30.

Reported-by: syzbot+df7dc146ebdd6435eea3@syzkaller.appspotmail.com
Cc: <stable@vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
---
 sound/core/oss/pcm_oss.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/sound/core/oss/pcm_oss.c b/sound/core/oss/pcm_oss.c
index 327ec42a36b0..de1917484647 100644
--- a/sound/core/oss/pcm_oss.c
+++ b/sound/core/oss/pcm_oss.c
@@ -1935,11 +1935,15 @@ static int snd_pcm_oss_set_subdivide(struct snd_pcm_oss_file *pcm_oss_file, int
 static int snd_pcm_oss_set_fragment1(struct snd_pcm_substream *substream, unsigned int val)
 {
 	struct snd_pcm_runtime *runtime;
+	int fragshift;
 
 	runtime = substream->runtime;
 	if (runtime->oss.subdivision || runtime->oss.fragshift)
 		return -EINVAL;
-	runtime->oss.fragshift = val & 0xffff;
+	fragshift = val & 0xffff;
+	if (fragshift >= 31)
+		return -EINVAL;
+	runtime->oss.fragshift = fragshift;
 	runtime->oss.maxfrags = (val >> 16) & 0xffff;
 	if (runtime->oss.fragshift < 4)		/* < 16 */
 		runtime->oss.fragshift = 4;
-- 
2.26.2


      reply index

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-12-09  8:45 [PATCH 1/2] ALSA: usb-audio: " Takashi Iwai
2020-12-09  8:45 ` Takashi Iwai [this message]

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20201209084552.17109-2-tiwai@suse.de \
    --to=tiwai@suse.de \
    --cc=alsa-devel@alsa-project.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

Alsa-Devel Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/alsa-devel/0 alsa-devel/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 alsa-devel alsa-devel/ https://lore.kernel.org/alsa-devel \
		alsa-devel@alsa-project.org
	public-inbox-index alsa-devel

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.alsa-project.alsa-devel


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git