RE: [PATCH for-4.14] tools: fix error path of xendevicemodel_open()

[Paul Durrant <xadimgnik@xxxxxxxxx>]

> -----Original Message-----
> From: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> Sent: 10 June 2020 12:40
> To: Xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>
> Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>; Ian Jackson 
> <Ian.Jackson@xxxxxxxxxx>; Wei Liu
> <wl@xxxxxxx>; Juergen Gross <jgross@xxxxxxxx>; Paul Durrant <paul@xxxxxxx>
> Subject: [PATCH for-4.14] tools: fix error path of xendevicemodel_open()
> 
> c/s 6902cb00e03 "tools/libxendevicemodel: extract functions and add a compat
> layer" introduced calls to both xencall_open() and osdep_xendevicemodel_open()
> but failed to fix up the error path.
> 
> c/s f68c7c618a3 "libs/devicemodel: free xencall handle in error path in
> _open()" fixed up the xencall_open() aspect of the error path (missing the
> osdep_xendevicemodel_open() aspect), but positioned the xencall_close()
> incorrectly, creating the same pattern proved to be problematic by c/s
> 30a72f02870 "tools: fix error path of xenhypfs_open()".
> 
> Reposition xtl_logger_destroy(), and introduce the missing
> osdep_xendevicemodel_close().
> 
> Fixes: 6902cb00e03 ("tools/libxendevicemodel: extract functions and add a 
> compat layer")
> Fixes: f68c7c618a3 ("libs/devicemodel: free xencall handle in error path in 
> _open()")
> Backport: 4.9+
> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> ---
> CC: Ian Jackson <Ian.Jackson@xxxxxxxxxx>
> CC: Wei Liu <wl@xxxxxxx>
> CC: Juergen Gross <jgross@xxxxxxxx>
> CC: Paul Durrant <paul@xxxxxxx>
> 
> RFC - this is still broken.
> 

I'm slightly confused. Do you want this in 4.14 in this form or are you 
expecting to update it?

  Paul

> Failure to create the logger will still hit the NULL deference, in all of the
> stable libs, not just devicemodel.
> 
> Also, unless I'd triple checked the history, I was about to reintroduce the
> deadlock from c/s 9976f3874d4, because it totally counterintuitive wrong to
> expect setup and teardown in opposite orders.
> ---
>  tools/libs/devicemodel/core.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/libs/devicemodel/core.c b/tools/libs/devicemodel/core.c
> index db501d9e80..4d4063956d 100644
> --- a/tools/libs/devicemodel/core.c
> +++ b/tools/libs/devicemodel/core.c
> @@ -67,9 +67,10 @@ xendevicemodel_handle 
> *xendevicemodel_open(xentoollog_logger *logger,
>      return dmod;
> 
>  err:
> -    xtl_logger_destroy(dmod->logger_tofree);
> +    osdep_xendevicemodel_close(dmod);
>      xentoolcore__deregister_active_handle(&dmod->tc_ah);
>      xencall_close(dmod->xcall);
> +    xtl_logger_destroy(dmod->logger_tofree);
>      free(dmod);
>      return NULL;
>  }
> --
> 2.11.0