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Subject: Re: [BUG] arm64: an infinite loop in generic_perform_write()
To:     Matthew Wilcox <willy@infradead.org>
CC:     Mark Rutland <mark.rutland@arm.com>,
        Andrew Morton <akpm@linux-foundation.org>,
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From:   Chen Huang <chenhuang5@huawei.com>
Message-ID: <e5730b44-6aae-c486-8495-d170fdf9baa1@huawei.com>
Date:   Thu, 24 Jun 2021 11:52:53 +0800
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ÔÚ 2021/6/24 11:24, Matthew Wilcox дµÀ:
> On Thu, Jun 24, 2021 at 11:10:41AM +0800, Chen Huang wrote:
>> In userspace, I perform such operation:
>>
>>  	fd = open("/tmp/test", O_RDWR | O_SYNC);
>>         access_address = (char *)mmap(NULL, uio_size, PROT_READ, MAP_SHARED, uio_fd, 0);
>>         ret = write(fd, access_address + 2, sizeof(long));
> 
> ... you know that accessing this at unaligned offsets isn't going to
> work.  It's completely meaningless.  Why are you trying to do it?
> .
> 

Yeah, it's a wrong usage of access. But maybe it's still a problem
an userspace operation  makes the kernel crash.