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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Ferry Toth <fntoth@gmail.com>,
        Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
        Heikki Krogerus <heikki.krogerus@linux.intel.com>,
        "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
Subject: [PATCH 4.9 087/117] device property: Dont clear secondary pointer for shared primary firmware node
Date:   Mon,  9 Nov 2020 13:55:13 +0100
Message-Id: <20201109125029.822833733@linuxfoundation.org>
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References: <20201109125025.630721781@linuxfoundation.org>
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From: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

commit 99aed9227073fb34ce2880cbc7063e04185a65e1 upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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

--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -2348,6 +2348,7 @@ static inline bool fwnode_is_primary(str
  */
 void set_primary_fwnode(struct device *dev, struct fwnode_handle *fwnode)
 {
+	struct device *parent = dev->parent;
 	struct fwnode_handle *fn = dev->fwnode;
 
 	if (fwnode) {
@@ -2362,7 +2363,8 @@ void set_primary_fwnode(struct device *d
 	} 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;
 		}