linux-kernel - Re: [PATCH 4.4 013/193] staging: android: ion: Add __GFP

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Date:   Fri, 23 Feb 2018 13:46:08 -0700
From:   Nathan Chancellor <natechancellor@...il.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        syzbot+76e7efc4748495855a4d@...kaller.appspotmail.com,
        syzbot <syzkaller@...glegroups.com>,
        Laura Abbott <labbott@...hat.com>
Subject: Re: [PATCH 4.4 013/193] staging: android: ion: Add __GFP_NOWARN for
 system contig heap

On Fri, Feb 23, 2018 at 07:24:06PM +0100, Greg Kroah-Hartman wrote:
> 4.4-stable review patch.  If anyone has any objections, please let me know.
> 
> ------------------
> 
> From: Laura Abbott <labbott@...hat.com>
> 
> commit 0c75f10312a35b149b2cebb1832316b35c2337ca upstream.
> 
> syzbot reported a warning from Ion:
> 
>   WARNING: CPU: 1 PID: 3485 at mm/page_alloc.c:3926
> 
>   ...
>    __alloc_pages_nodemask+0x9fb/0xd80 mm/page_alloc.c:4252
>   alloc_pages_current+0xb6/0x1e0 mm/mempolicy.c:2036
>   alloc_pages include/linux/gfp.h:492 [inline]
>   ion_system_contig_heap_allocate+0x40/0x2c0
>   drivers/staging/android/ion/ion_system_heap.c:374
>   ion_buffer_create drivers/staging/android/ion/ion.c:93 [inline]
>   ion_alloc+0x2c1/0x9e0 drivers/staging/android/ion/ion.c:420
>   ion_ioctl+0x26d/0x380 drivers/staging/android/ion/ion-ioctl.c:84
>   vfs_ioctl fs/ioctl.c:46 [inline]
>   do_vfs_ioctl+0x1b1/0x1520 fs/ioctl.c:686
>   SYSC_ioctl fs/ioctl.c:701 [inline]
>   SyS_ioctl+0x8f/0xc0 fs/ioctl.c:692
> 
> This is a warning about attempting to allocate order > MAX_ORDER. This
> is coming from a userspace Ion allocation request. Since userspace is
> free to request however much memory it wants (and the kernel is free to
> deny its allocation), silence the allocation attempt with __GFP_NOWARN
> in case it fails.
> 
> Reported-by: syzbot+76e7efc4748495855a4d@...kaller.appspotmail.com
> Reported-by: syzbot <syzkaller@...glegroups.com>
> Signed-off-by: Laura Abbott <labbott@...hat.com>
> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> 
> ---
>  drivers/staging/android/ion/ion_system_heap.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> --- a/drivers/staging/android/ion/ion_system_heap.c
> +++ b/drivers/staging/android/ion/ion_system_heap.c
> @@ -336,7 +336,7 @@ static int ion_system_contig_heap_alloca
>  	if (align > (PAGE_SIZE << order))
>  		return -EINVAL;
>  
> -	page = alloc_pages(low_order_gfp_flags, order);
> +	page = alloc_pages(low_order_gfp_flags | __GFP_NOWARN, order);
>  	if (!page)
>  		return -ENOMEM;
>  
> 
>

This commit is not necessary as __GFP_NOWARN is still in the global
low_order_gfp_flags since commit d2805d7fff5b ("staging: ion: remove
__GFP_NOWARN when use low order gfp flags") did not show up until 4.9.
This also applies to 3.18.

Thanks!
Nathan