[libvirt] [PATCH v2] util: Set backing file name for LOOP_GET_STATUS64 queries.

[Daniel P. Berrangé]

On Mon, Sep 02, 2019 at 02:00:27PM -0300, jcfaracco at gmail.com wrote:
> From: Julio Faracco <jcfaracco at gmail.com>
> 
> This is an issue for LXC loop devices when you are trying to get loop
> devices info using `ioctl`. Modern apps uses `/sys/dev/block` to grab
> information about devices, but if you use the method mention you won't
> be able to retrive the associated file with that loop device. See
> example below from cryptsetup sources:
> 
>     static char *_ioctl_backing_file(const char *loop)
>     {
>         struct loop_info64 lo64 = {0};
>         int loop_fd;
> 
>         loop_fd = open(loop, O_RDONLY);
>         if (loop_fd < 0)
>             return NULL;
> 
>         if (ioctl(loop_fd, LOOP_GET_STATUS64, &lo64) < 0) {
>             close(loop_fd);
>             return NULL;
>         }
> 
>         lo64.lo_file_name[LO_NAME_SIZE-2] = '*';
>         lo64.lo_file_name[LO_NAME_SIZE-1] = 0;
> 
>         close(loop_fd);
>         return strdup((char*)lo64.lo_file_name);
>     }
> 
> It will return an empty string because lo_file_name was not set.
> Function `virFileLoopDeviceOpenSearch()` is using `ioctl` to query data,
> but it is not checking `lo_file_name` field.
> 
> v1: I accidentally committed two wrong lines.

This type of message should be put after the "---" lines...

> 
> Signed-off-by: Julio Faracco <jcfaracco at gmail.com>
> ---

Here, so that it doesn't get into git history when the patch
is applied

>  src/util/virfile.c | 8 ++++++++
>  1 file changed, 8 insertions(+)

Reviewed-by: Daniel P. Berrangé <berrange at redhat.com>

and pushed to git


Regards,
Daniel
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