Re: [PATCH for-9.1 6/9] block/nbd: Use URI parsing code from glib

[Thomas Huth <thuth@redhat.com>]

On 23/09/2024 18.03, Eric Blake wrote:
> On Sun, Sep 22, 2024 at 08:51:22PM GMT, Richard W.M. Jones wrote:
>> On Thu, Mar 28, 2024 at 02:13:42PM +0000, Richard W.M. Jones wrote:
>>> On Thu, Mar 28, 2024 at 03:06:03PM +0100, Thomas Huth wrote:
>>>> Since version 2.66, glib has useful URI parsing functions, too.
>>>> Use those instead of the QEMU-internal ones to be finally able
>>>> to get rid of the latter. The g_uri_get_host() also takes care
>>>> of removing the square brackets from IPv6 addresses, so we can
>>>> drop that part of the QEMU code now, too.
>>>>
> 
>>>>   
>>>> -    p = uri->path ? uri->path : "";
>>>> +    p = g_uri_get_path(uri) ?: "";
>>>>       if (p[0] == '/') {
>>>>           p++;
>>>>       }
> 
>>> Looks ok,
>>>
>>> Reviewed-by: Richard W.M. Jones <rjones@redhat.com>
>>
>> Or maybe not.  This caused a regression in the nbdkit test suite (when
>> we use qemu-img from 9.1).  It seems the exportname part of the NBD
>> URI gets munged:
>>
>> https://gitlab.com/qemu-project/qemu/-/issues/2584
> 
> To be more specific, it looks like
> g_uri_get_path("./name//with//..//slashes") is getting munged to
> "name/slashes".  That is, glib is blindly assuming that ./ and XXX/../
> can be dropped, and // can be simplified to /, which may be true for
> arbitrary file names but not true for abitrary URIs (since URIs have
> application-specific semantics, which may not match path name
> traversal semantics).  Looks like we need to report a bug to glib,
> and/or see if glib's URI functions have a flag for turning off this
> unwanted munging.
> 
> Or we may just want to document this corner case change as
> intentional.

Ok ... so how bad is this for NBD? Can we go along with the odditiy or is 
this breaking some real world NBD scenarios?

... in the worst case, we have to revert the patch ...

  Thomas