From: Stefano Stabellini <stefano.stabellini@xilinx.com>

In case of errors in xenbus_init (e.g. missing xen_store_gfn parameter),
we goto out_error but we forget to reset xen_store_domain_type to
XS_UNKNOWN. As a consequence xenbus_probe_initcall and other initcalls
will still try to initialize xenstore resulting into a crash at boot.

[    2.479830] Call trace:
[    2.482314]  xb_init_comms+0x18/0x150
[    2.486354]  xs_init+0x34/0x138
[    2.489786]  xenbus_probe+0x4c/0x70
[    2.498432]  xenbus_probe_initcall+0x2c/0x7c
[    2.503944]  do_one_initcall+0x54/0x1b8
[    2.507358]  kernel_init_freeable+0x1ac/0x210
[    2.511617]  kernel_init+0x28/0x130
[    2.516112]  ret_from_fork+0x10/0x20

Cc: <Stable@vger.kernel.org>
Signed-off-by: Stefano Stabellini <stefano.stabellini@xilinx.com>
---
 drivers/xen/xenbus/xenbus_probe.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/xen/xenbus/xenbus_probe.c b/drivers/xen/xenbus/xenbus_probe.c
index bd003ca8acbe..34abf2b5967b 100644
--- a/drivers/xen/xenbus/xenbus_probe.c
+++ b/drivers/xen/xenbus/xenbus_probe.c
@@ -983,8 +983,10 @@ static int __init xenbus_init(void)
 	 */
 	proc_create_mount_point("xen");
 #endif
+	return err;
 
 out_error:
+	xen_store_domain_type = XS_UNKNOWN;
 	return err;
 }
 
-- 
2.25.1

On 12.11.2021 22:47, Stefano Stabellini wrote:
> --- a/drivers/xen/xenbus/xenbus_probe.c
> +++ b/drivers/xen/xenbus/xenbus_probe.c
> @@ -983,8 +983,10 @@ static int __init xenbus_init(void)
>  	 */
>  	proc_create_mount_point("xen");
>  #endif
> +	return err;

Personally I think such cases would better be "return 0". With
that done here, err's initializer could (imo should) then also
be dropped.

Jan

>  out_error:
> +	xen_store_domain_type = XS_UNKNOWN;
>  	return err;
>  }
>  
> 

On Mon, 15 Nov 2021, Jan Beulich wrote:
> On 12.11.2021 22:47, Stefano Stabellini wrote:
> > --- a/drivers/xen/xenbus/xenbus_probe.c
> > +++ b/drivers/xen/xenbus/xenbus_probe.c
> > @@ -983,8 +983,10 @@ static int __init xenbus_init(void)
> >  	 */
> >  	proc_create_mount_point("xen");
> >  #endif
> > +	return err;
> 
> Personally I think such cases would better be "return 0". With
> that done here, err's initializer could (imo should) then also
> be dropped.

I'll make both changes in the next version


> >  out_error:
> > +	xen_store_domain_type = XS_UNKNOWN;
> >  	return err;
> >  }
> >  
> > 
>