Re: [Qemu-devel] [PATCH v2] file-posix: specify expected filetypes

[Eric Blake]

On 01/15/2018 04:50 PM, John Snow wrote:
> 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>
> ---
> 

> @@ -556,10 +557,30 @@ static int raw_open_common(BlockDriverState *bs, QDict 
> *options,
>          error_setg_errno(errp, errno, "Could not stat file");
>          goto fail;
>      }
> -    if (S_ISREG(st.st_mode)) {
> -        s->discard_zeroes = true;
> -        s->has_fallocate = true;
> +
> +    if (!device) {
> +        if (S_ISBLK(st.st_mode)) {
> +            warn_report("Opening a block device as file using 'file'"
> +                        "driver is deprecated");

Do we have a proper deprecation documentation in place, and a time frame
for when we'd start rejecting this rather than permitting it with the
warning?

> +        } else if (S_ISCHR(st.st_mode)) {
> +            warn_report("Opening a character device as file using the 'file'"
> +                        "driver is deprecated");
> +        } else if (!S_ISREG(st.st_mode)) {
> +            error_setg(errp, "A regular file was expected by the 'file' 
> driver,"
> +                       "but something else was given");

This makes sense.


> @@ -589,7 +610,6 @@ static int raw_open_common(BlockDriverState *bs, QDict 
> *options,
>          s->needs_alignment = true;
>      }
>  #endif
> -
>  #ifdef CONFIG_XFS
>      if (platform_test_xfs_fd(s->fd)) {

Spurious whitespace change.

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

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