From: Takashi Iwai <redacted>

commit 8839c8c0f77ab8fc0463f4ab8b37fca3f70677c2 upstream.

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 <redacted>
Cc: <redacted>
Link: https://lore.kernel.org/r/1638270978-42412-1-git-send-email-cuibixuan@linux.alibaba.com (local)
Link: https://lore.kernel.org/r/20211201073606.11660-3-tiwai@suse.de (local)
Signed-off-by: Takashi Iwai <redacted>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 sound/core/oss/pcm_oss.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/sound/core/oss/pcm_oss.c
+++ b/sound/core/oss/pcm_oss.c

@@ -1952,7 +1952,7 @@ static int snd_pcm_oss_set_fragment1(str
 	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;