Patch "ALSA: usx2y: Suppress kernel warning at page allocation failures" has been added to the 4.13-stable tree

This is a note to let you know that I've just added the patch titled

ALSA: usx2y: Suppress kernel warning at page allocation failures

to the 4.13-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
alsa-usx2y-suppress-kernel-warning-at-page-allocation-failures.patch
and it can be found in the queue-4.13 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Takashi Iwai <[email protected]>
Date: Mon, 2 Oct 2017 14:06:43 +0200
Subject: ALSA: usx2y: Suppress kernel warning at page allocation failures

From: Takashi Iwai <[email protected]>

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.

---
 sound/usb/usx2y/usb_stream.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

@@ -191,7 +191,8 @@ 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;

@@ -211,7 +212,8 @@ 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);

Patches currently in stable-queue which might be from [email protected] are

queue-4.13/alsa-usx2y-suppress-kernel-warning-at-page-allocation-failures.patch queue-4.13/alsa-usb-audio-check-out-of-bounds-access-by-corrupted-buffer-descriptor.patch queue-4.13/revert-alsa-echoaudio-purge-contradictions-between-dimension-matrix-members-and-total-number-of-members.patch queue-4.13/alsa-compress-remove-unused-variable.patch