From 8839c8c0f77ab8fc0463f4ab8b37fca3f70677c2 Mon Sep 17 00:00:00 2001
From: Takashi Iwai <tiwai@suse.de>
Date: Wed, 1 Dec 2021 08:36:05 +0100
Subject: [PATCH] ALSA: pcm: oss: Limit the period size to 16MB
Git-commit: 8839c8c0f77ab8fc0463f4ab8b37fca3f70677c2
Patch-mainline: v5.16-rc5
References: git-fixes

Set the practical limit to the period size (the fragment shift in OSS)
instead of a full 31bit; a too large value could lead to the exhaust
of memory as we allocate temporary buffers of the period size, too.

As of this patch, we set to 16MB limit, which should cover all use
cases.

Reported-by: syzbot+bb348e9f9a954d42746f@syzkaller.appspotmail.com
Reported-by: Bixuan Cui <cuibixuan@linux.alibaba.com>
Cc: <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/1638270978-42412-1-git-send-email-cuibixuan@linux.alibaba.com
Link: https://lore.kernel.org/r/20211201073606.11660-3-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>

---
 sound/core/oss/pcm_oss.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/sound/core/oss/pcm_oss.c b/sound/core/oss/pcm_oss.c
index bec7590bc84b..89c4910daf02 100644
--- a/sound/core/oss/pcm_oss.c
+++ b/sound/core/oss/pcm_oss.c
@@ -1962,7 +1962,7 @@ static int snd_pcm_oss_set_fragment1(struct snd_pcm_substream *substream, unsign
 	if (runtime->oss.subdivision || runtime->oss.fragshift)
 		return -EINVAL;
 	fragshift = val & 0xffff;
-	if (fragshift >= 31)
+	if (fragshift >= 25) /* should be large enough */
 		return -EINVAL;
 	runtime->oss.fragshift = fragshift;
 	runtime->oss.maxfrags = (val >> 16) & 0xffff;
-- 
2.31.1