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ALSA: usx2y: Suppress kernel warning at page allocation failures
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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 <[email protected]>
Tested-by: Andrey Konovalov <[email protected]>
Cc: <[email protected]>
Signed-off-by: Takashi Iwai <[email protected]>
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tiwai committed Oct 2, 2017
1 parent 51db452 commit 7682e39
Showing 1 changed file with 4 additions and 2 deletions.
6 changes: 4 additions & 2 deletions sound/usb/usx2y/usb_stream.c
Original file line number Diff line number Diff line change
Expand Up @@ -191,7 +191,8 @@ struct usb_stream *usb_stream_new(struct usb_stream_kernel *sk,
}

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;
Expand All @@ -211,7 +212,8 @@ struct usb_stream *usb_stream_new(struct usb_stream_kernel *sk,
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);
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