linux-kernel - [PATCH 4.8 02/92] ALSA: info: Limit the proc text input size

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Date:   Thu, 17 Nov 2016 11:31:35 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Takashi Iwai <tiwai@...e.de>
Subject: [PATCH 4.8 02/92] ALSA: info: Limit the proc text input size

4.8-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Takashi Iwai <tiwai@...e.de>

commit 027a9fe6835620422b6713892175716f3613dd9d upstream.

The ALSA proc handler allows currently the write in the unlimited size
until kmalloc() fails.  But basically the write is supposed to be only
for small inputs, mostly for one line inputs, and we don't have to
handle too large sizes at all.  Since the kmalloc error results in the
kernel warning, it's better to limit the size beforehand.

This patch adds the limit of 16kB, which must be large enough for the
currently existing code.

Signed-off-by: Takashi Iwai <tiwai@...e.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 sound/core/info.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/sound/core/info.c
+++ b/sound/core/info.c
@@ -331,6 +331,9 @@ static ssize_t snd_info_text_entry_write
 	if (!valid_pos(pos, count))
 		return -EIO;
 	next = pos + count;
+	/* don't handle too large text inputs */
+	if (next > 16 * 1024)
+		return -EIO;
 	mutex_lock(&entry->access);
 	buf = data->wbuffer;
 	if (!buf) {