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Date:   Sat, 11 Sep 2021 13:54:17 +0200
From:   Greg KH <gregkh@linuxfoundation.org>
To:     Cheng Chao <cs.os.kernel@gmail.com>
Cc:     labbott@redhat.com, sumit.semwal@linaro.org, arve@android.com,
        riandrews@android.com, devel@driverdev.osuosl.org,
        stable@vger.kernel.org
Subject: Re: [PATCH] [PATCH 4.9] staging: android: ion: fix page is NULL
Message-ID: <YTyY6ZALBhCm47T6@kroah.com>
References: <20210911112115.47202-1-cs.os.kernel@gmail.com>
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On Sat, Sep 11, 2021 at 07:21:15PM +0800, Cheng Chao wrote:
> kernel panic is here:
> 
> Unable to handle kernel paging request at virtual address b0380000
> pgd = d9d94000
> [b0380000] *pgd=00000000
> Internal error: Oops: 2805 [#1] PREEMPT SMP ARM
> ...
> task: daa2dd00 task.stack: da194000
> PC is at v7_dma_clean_range+0x1c/0x34
> LR is at arm_dma_sync_single_for_device+0x44/0x58
> pc : [<c011aa0c>]    lr : [<c011645c>]    psr: 200f0013
> sp : da195da0  ip : dc1f9000  fp : c1043dc4
> r10: 00000000  r9 : c16f1f58  r8 : 00000001
> r7 : c1621f94  r6 : c0116418  r5 : 00000000  r4 : c011aa58
> r3 : 0000003f  r2 : 00000040  r1 : b0480000  r0 : b0380000
> Flags: nzCv  IRQs on  FIQs on  Mode SVC_32  ISA ARM  Segment none
> Control: 10c5383d  Table: 19d9406a  DAC: 00000051
> ...
> [<c011aa0c>] (v7_dma_clean_range) from [<c011645c>] (arm_dma_sync_single_for_device+0x44/0x58)
> [<c011645c>] (arm_dma_sync_single_for_device) from [<c0117088>] (arm_dma_sync_sg_for_device+0x50/0x7c)
> [<c0117088>] (arm_dma_sync_sg_for_device) from [<c0c033c4>] (ion_pages_sync_for_device+0xb0/0xec)
> [<c0c033c4>] (ion_pages_sync_for_device) from [<c0c054ac>] (ion_system_heap_allocate+0x2a0/0x2e0)
> [<c0c054ac>] (ion_system_heap_allocate) from [<c0c02c78>] (ion_alloc+0x12c/0x494)
> [<c0c02c78>] (ion_alloc) from [<c0c03eac>] (ion_ioctl+0x510/0x63c)
> [<c0c03eac>] (ion_ioctl) from [<c027c4b0>] (do_vfs_ioctl+0xa8/0x9b4)
> [<c027c4b0>] (do_vfs_ioctl) from [<c027ce28>] (SyS_ioctl+0x6c/0x7c)
> [<c027ce28>] (SyS_ioctl) from [<c0108a40>] (ret_fast_syscall+0x0/0x48)
> Code: e3a02004 e1a02312 e2423001 e1c00003 (ee070f3a)
> ---[ end trace 89278304932c0e87 ]---
> Kernel panic - not syncing: Fatal exception
> 
> Signed-off-by: Cheng Chao <cs.os.kernel@gmail.com>
> ---
>  drivers/staging/android/ion/ion_system_heap.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/staging/android/ion/ion_system_heap.c b/drivers/staging/android/ion/ion_system_heap.c
> index 22c481f2ae4f..2a35b99cf628 100644
> --- a/drivers/staging/android/ion/ion_system_heap.c
> +++ b/drivers/staging/android/ion/ion_system_heap.c
> @@ -75,7 +75,7 @@ static struct page *alloc_buffer_page(struct ion_system_heap *heap,
>  
>  	page = ion_page_pool_alloc(pool);
>  
> -	if (cached)
> +	if (page && cached)
>  		ion_pages_sync_for_device(NULL, page, PAGE_SIZE << order,
>  					  DMA_BIDIRECTIONAL);
>  	return page;
> -- 
> 2.26.3
> 

Why is this just a 4.9 patch?  Ion didn't get removed until 5.11, so
wouldn't this be an issue for anything 5.10 and older?

thanks,

greg k-h