Merge tag 'v5.16-rc5' into locking/core, to pick up fixes

Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 26 insertions, 1 deletions

diff --git a/drivers/xen/xenbus/xenbus_probe.c b/drivers/xen/xenbus/xenbus_probe.c
index bd003ca8acbe..fe360c33ce71 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;
 
@@ -949,6 +949,29 @@ static int __init xenbus_init(void)
 		err = hvm_get_parameter(HVM_PARAM_STORE_PFN, &v);
 		if (err)
 			goto out_error;
+		/*
+		 * Uninitialized hvm_params are zero and return no error.
+		 * Although it is theoretically possible to have
+		 * HVM_PARAM_STORE_PFN set to zero on purpose, in reality it is
+		 * not zero when valid. If zero, it means that Xenstore hasn't
+		 * been properly initialized. Instead of attempting to map a
+		 * wrong guest physical address return error.
+		 *
+		 * Also recognize all bits set as an invalid value.
+		 */
+		if (!v || !~v) {
+			err = -ENOENT;
+			goto out_error;
+		}
+		/* Avoid truncation on 32-bit. */
+#if BITS_PER_LONG == 32
+		if (v > ULONG_MAX) {
+			pr_err("%s: cannot handle HVM_PARAM_STORE_PFN=%llx > ULONG_MAX\n",
+			       __func__, v);
+			err = -EINVAL;
+			goto out_error;
+		}
+#endif
 		xen_store_gfn = (unsigned long)v;
 		xen_store_interface =
 			xen_remap(xen_store_gfn << XEN_PAGE_SHIFT,
@@ -983,8 +1006,10 @@ static int __init xenbus_init(void)
 	 */
 	proc_create_mount_point("xen");
 #endif
+	return 0;
 
 out_error:
+	xen_store_domain_type = XS_UNKNOWN;
 	return err;
 }