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Re: [Qemu-block] [Qemu-devel] [PATCH v4] file-posix: specify expected fi

From: Eric Blake
Subject: Re: [Qemu-block] [Qemu-devel] [PATCH v4] file-posix: specify expected filetypes
Date: Fri, 19 Jan 2018 17:03:27 -0600
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.5.2

On 01/19/2018 04:47 PM, John Snow wrote:
> Adjust each caller of raw_open_common to specify if they are expecting
> host and character devices or not. Tighten expectations of file types upon
> open in the common code and refuse types that are not expected.
> This has two effects:
> (1) Character and block devices are now considered deprecated for the
>     'file' driver, which expects only S_IFREG, and
> (2) no file-posix driver (file, host_cdrom, or host_device) can open
>     directories now.
> I don't think there's a legitimate reason to open directories as if
> they were files. This prevents QEMU from opening and attempting to probe
> a directory inode, which can break in exciting ways. One of those ways
> is lseek on ext4/xfs, which will return 0x7fffffffffffffff as the file
> size instead of EISDIR. This can coax QEMU into responding with a
> confusing "file too big" instead of "Hey, that's not a file".
> See: https://bugs.launchpad.net/qemu/+bug/1739304/
> Signed-off-by: John Snow <address@hidden>
> ---

Reviewed-by: Eric Blake <address@hidden>

Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org

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