On 10/09/2012 11:56 PM, Jeff Cody wrote:
> Currently, bdrv_find_backing_image compares bs->backing_file with
> what is passed in as a backing_file name. Mismatches may occur,
> however, when bs->backing_file and backing_file are both not
> absolute or relative.
>
> Use path_combine() to make sure any relative backing filenames are
> relative to the current image filename being searched, and then use
> realpath() to make all comparisons based on absolute filenames.
>
> This also changes bdrv_find_backing_image to no longer be recursive,
> but iterative.
>
> Signed-off-by: Jeff Cody <jc...@redhat.com>
> ---
> block.c | 38 ++++++++++++++++++++++++++++++++------
> 1 file changed, 32 insertions(+), 6 deletions(-)
>
> diff --git a/block.c b/block.c
> index e95f613..641b8fa 100644
> --- a/block.c
> +++ b/block.c
> @@ -3123,18 +3123,44 @@ int bdrv_snapshot_load_tmp(BlockDriverState *bs,
> return -ENOTSUP;
> }
>
> +/* backing_file can either be relative, or absolute. If it is
> + * relative, it must be relative to the chain. So, passing in
> + * bs->filename from a BDS as backing_file should not be done,
> + * as that may be relative to the CWD rather than the chain. */
> BlockDriverState *bdrv_find_backing_image(BlockDriverState *bs,
> const char *backing_file)
> {
> - if (!bs->drv) {
> + char filename_full[PATH_MAX];
> + char backing_file_full[PATH_MAX];
> + char filename_tmp[PATH_MAX];That's a LOT of stack space, which risks stack overflow, will mostly be unused, and still doesn't work if you have super-deep hierarchies larger than PATH_MAX. Would you be better off using realpath(,NULL) for its allocating semantics, and then free()ing the results? -- Eric Blake ebl...@redhat.com +1-919-301-3266 Libvirt virtualization library http://libvirt.org
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