linux-kernel - [PATCH 3.2 36/94] ALSA: usx2y: Suppress kernel warning at page allocation failures

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Date:   Thu, 28 Dec 2017 16:59:12 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org,
        "Andrey Konovalov" <andreyknvl@...gle.com>,
        "Takashi Iwai" <tiwai@...e.de>
Subject: [PATCH 3.2 36/94] ALSA: usx2y: Suppress kernel warning at page
 allocation failures

3.2.97-rc1 review patch.  If anyone has any objections, please let me know.

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

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

commit 7682e399485fe19622b6fd82510b1f4551e48a25 upstream.

The usx2y driver allocates the stream read/write buffers in continuous
pages depending on the stream setup, and this may spew the kernel
warning messages with a stack trace like:
  WARNING: CPU: 1 PID: 1846 at mm/page_alloc.c:3883
  __alloc_pages_slowpath+0x1ef2/0x2d70
  Modules linked in:
  CPU: 1 PID: 1846 Comm: kworker/1:2 Not tainted
  ....

It may confuse user as if it were any serious error, although this is
no fatal error and the driver handles the error case gracefully.
Since the driver has already some sanity check of the given size (128
and 256 pages), it can't pass any crazy value.  So it's merely page
fragmentation.

This patch adds __GFP_NOWARN to each caller for suppressing such
kernel warnings.  The original issue was spotted by syzkaller.

Reported-by: Andrey Konovalov <andreyknvl@...gle.com>
Tested-by: Andrey Konovalov <andreyknvl@...gle.com>
Signed-off-by: Takashi Iwai <tiwai@...e.de>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 sound/usb/usx2y/usb_stream.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

--- a/sound/usb/usx2y/usb_stream.c
+++ b/sound/usb/usx2y/usb_stream.c
@@ -192,7 +192,8 @@ struct usb_stream *usb_stream_new(struct
 	}

 	pg = get_order(read_size);
-	sk->s = (void *) __get_free_pages(GFP_KERNEL|__GFP_COMP|__GFP_ZERO, pg);
+	sk->s = (void *) __get_free_pages(GFP_KERNEL|__GFP_COMP|__GFP_ZERO|
+					  __GFP_NOWARN, pg);
 	if (!sk->s) {
 		snd_printk(KERN_WARNING "couldn't __get_free_pages()\n");
 		goto out;
@@ -212,7 +213,8 @@ struct usb_stream *usb_stream_new(struct
 	pg = get_order(write_size);

 	sk->write_page =
-		(void *)__get_free_pages(GFP_KERNEL|__GFP_COMP|__GFP_ZERO, pg);
+		(void *)__get_free_pages(GFP_KERNEL|__GFP_COMP|__GFP_ZERO|
+					 __GFP_NOWARN, pg);
 	if (!sk->write_page) {
 		snd_printk(KERN_WARNING "couldn't __get_free_pages()\n");
 		usb_stream_free(sk);