genirq: Properly pair kobject_del() with kobject_add()

commit d0ff14fdc987303aeeb7de6f1bd72c3749ae2a9b upstream.

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

diff --git a/kernel/irq/irqdesc.c b/kernel/irq/irqdesc.c
index 8e009ce..26814a1 100644 (file)
--- a/kernel/irq/irqdesc.c
+++ b/kernel/irq/irqdesc.c
@@ -294,6 +294,18 @@ 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;
@@ -324,6 +336,7 @@ 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 */
 
@@ -437,7 +450,7 @@ 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);
 
        /*