From 99aed9227073fb34ce2880cbc7063e04185a65e1 Mon Sep 17 00:00:00 2001
From: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Date: Thu, 22 Oct 2020 21:41:00 +0300
Subject: [PATCH] device property: Don't clear secondary pointer for shared primary firmware node
Git-commit: 99aed9227073fb34ce2880cbc7063e04185a65e1
Patch-mainline: v5.10-rc2
References: git-fixes

It appears that firmware nodes can be shared between devices. In such case
when a (child) device is about to be deleted, its firmware node may be shared
and ACPI_COMPANION_SET(..., NULL) call for it breaks the secondary link
of the shared primary firmware node.

In order to prevent that, check, if the device has a parent and parent's
firmware node is shared with its child, and avoid crashing the link.

Fixes: c15e1bdda436 ("device property: Fix the secondary firmware node handling in set_primary_fwnode()")
Reported-by: Ferry Toth <fntoth@gmail.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Tested-by: Ferry Toth <fntoth@gmail.com>
Cc: 5.9+ <stable@vger.kernel.org> # 5.9+
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/base/core.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/base/core.c b/drivers/base/core.c
index 41feab679fa1..78114ddac755 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -4264,6 +4264,7 @@ static inline bool fwnode_is_primary(struct fwnode_handle *fwnode)
  */
 void set_primary_fwnode(struct device *dev, struct fwnode_handle *fwnode)
 {
+	struct device *parent = dev->parent;
 	struct fwnode_handle *fn = dev->fwnode;
 
 	if (fwnode) {
@@ -4278,7 +4279,8 @@ void set_primary_fwnode(struct device *dev, struct fwnode_handle *fwnode)
 	} else {
 		if (fwnode_is_primary(fn)) {
 			dev->fwnode = fn->secondary;
-			fn->secondary = ERR_PTR(-ENODEV);
+			if (!(parent && fn == parent->fwnode))
+				fn->secondary = ERR_PTR(-ENODEV);
 		} else {
 			dev->fwnode = NULL;
 		}
-- 
2.16.4