linux-kernel - Re: [BUG] arm64: an infinite loop in generic_perform

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Message-ID: <e5730b44-6aae-c486-8495-d170fdf9baa1@huawei.com>
Date:   Thu, 24 Jun 2021 11:52:53 +0800
From:   Chen Huang <chenhuang5@...wei.com>
To:     Matthew Wilcox <willy@...radead.org>
CC:     Mark Rutland <mark.rutland@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Stephen Rothwell <sfr@...b.auug.org.au>,
        Al Viro <viro@...iv.linux.org.uk>,
        Randy Dunlap <rdunlap@...radead.org>,
        "Catalin Marinas" <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        linux-mm <linux-mm@...ck.org>,
        "open list" <linux-kernel@...r.kernel.org>
Subject: Re: [BUG] arm64: an infinite loop in generic_perform_write()



在 2021/6/24 11:24, Matthew Wilcox 写道:
> 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.