From:   Stefano Stabellini <sstabellini@kernel.org>
To:     jgross@suse.com
Cc:     boris.ostrovsky@oracle.com, xen-devel@lists.xenproject.org,
        linux-kernel@vger.kernel.org, sstabellini@kernel.org,
        Stefano Stabellini <stefano.stabellini@xilinx.com>,
        Stable@vger.kernel.org, jbeulich@suse.com
Subject: [PATCH v2] xen: don't continue xenstore initialization in case of errors
Date:   Mon, 15 Nov 2021 14:27:19 -0800
Message-Id: <20211115222719.2558207-1-sstabellini@kernel.org>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

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>
Cc: jbeulich@suse.com
Signed-off-by: Stefano Stabellini <stefano.stabellini@xilinx.com>
---
Changes in v2:
- use return 0 for the success case
- remove err initializer as it is not useful any longer
---
 drivers/xen/xenbus/xenbus_probe.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/xen/xenbus/xenbus_probe.c b/drivers/xen/xenbus/xenbus_probe.c
index bd003ca8acbe..5967aa937255 100644
--- a/drivers/xen/xenbus/xenbus_probe.c
+++ b/drivers/xen/xenbus/xenbus_probe.c
@@ -909,7 +909,7 @@ static struct notifier_block xenbus_resume_nb = {
 
 static int __init xenbus_init(void)
 {
-	int err = 0;
+	int err;
 	uint64_t v = 0;
 	xen_store_domain_type = XS_UNKNOWN;
 
@@ -983,8 +983,10 @@ static int __init xenbus_init(void)
 	 */
 	proc_create_mount_point("xen");
 #endif
+	return 0;
 
 out_error:
+	xen_store_domain_type = XS_UNKNOWN;
 	return err;
 }
 
-- 
2.25.1