From d0ff14fdc987303aeeb7de6f1bd72c3749ae2a9b Mon Sep 17 00:00:00 2001
From: Michael Kelley <mikelley@microsoft.com>
Date: Thu, 1 Aug 2019 23:53:53 +0000
Subject: [PATCH] genirq: Properly pair kobject_del() with kobject_add()
Git-commit: d0ff14fdc987303aeeb7de6f1bd72c3749ae2a9b
Patch-mainline: v5.3-rc6
References: bsc#1051510

If alloc_descs() fails before irq_sysfs_init() has run, free_desc() in the
cleanup path will call kobject_del() even though the kobject has not been
added with kobject_add().

Fix this by making the call to kobject_del() conditional on whether
irq_sysfs_init() has run.

This problem surfaced because commit aa30f47cf666 ("kobject: Add support
for default attribute groups to kobj_type") makes kobject_del() stricter
about pairing with kobject_add(). If the pairing is incorrrect, a WARNING
and backtrace occur in sysfs_remove_group() because there is no parent.

[ tglx: Add a comment to the code and make it work with CONFIG_SYSFS=n ]

Fixes: ecb3f394c5db ("genirq: Expose interrupt information through sysfs")
Signed-off-by: Michael Kelley <mikelley@microsoft.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/1564703564-4116-1-git-send-email-mikelley@microsoft.com
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 kernel/irq/irqdesc.c | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/kernel/irq/irqdesc.c b/kernel/irq/irqdesc.c
index 9484e88dabc2..9be995fc3c5a 100644
--- a/kernel/irq/irqdesc.c
+++ b/kernel/irq/irqdesc.c
@@ -295,6 +295,18 @@ static void irq_sysfs_add(int irq, struct irq_desc *desc)
 	}
 }
 
+static void irq_sysfs_del(struct irq_desc *desc)
+{
+	/*
+	 * If irq_sysfs_init() has not yet been invoked (early boot), then
+	 * irq_kobj_base is NULL and the descriptor was never added.
+	 * kobject_del() complains about a object with no parent, so make
+	 * it conditional.
+	 */
+	if (irq_kobj_base)
+		kobject_del(&desc->kobj);
+}
+
 static int __init irq_sysfs_init(void)
 {
 	struct irq_desc *desc;
@@ -325,6 +337,7 @@ static struct kobj_type irq_kobj_type = {
 };
 
 static void irq_sysfs_add(int irq, struct irq_desc *desc) {}
+static void irq_sysfs_del(struct irq_desc *desc) {}
 
 #endif /* CONFIG_SYSFS */
 
@@ -438,7 +451,7 @@ static void free_desc(unsigned int irq)
 	 * The sysfs entry must be serialized against a concurrent
 	 * irq_sysfs_init() as well.
 	 */
-	kobject_del(&desc->kobj);
+	irq_sysfs_del(desc);
 	delete_irq_desc(irq);
 
 	/*
-- 
2.16.4