From 0db791c11d40b70122660a79beae7302e0a276d5 Mon Sep 17 00:00:00 2001
From: Thomas Gleixner <tglx@linutronix.de>
Date: Tue, 5 Sep 2017 10:12:20 +0200
Subject: [PATCH 01/10] genirq: Make sparse_irq_lock protect what it should
 protect

References: bsc#1070194
Patch-mainline: v4.14-rc1
Git-commit: 12ac1d0f6c3e95732d144ffa65c8b20fbd9aa462

for_each_active_irq() iterates the sparse irq allocation bitmap. The caller
must hold sparse_irq_lock. Several code pathes expect that an active bit in
the sparse bitmap also has a valid interrupt descriptor.

Unfortunately that's not true. The (de)allocation is a two step process,
which holds the sparse_irq_lock only across the queue/remove from the radix
tree and the set/clear in the allocation bitmap.

If a iteration locks sparse_irq_lock between the two steps, then it might
see an active bit but the corresponding irq descriptor is NULL. If that is
dereferenced unconditionally, then the kernel oopses. Of course, all
iterator sites could be audited and fixed, but....

There is no reason why the sparse_irq_lock needs to be dropped between the
two steps, in fact the code becomes simpler when the mutex is held across
both and the semantics become more straight forward, so future problems of
missing NULL pointer checks in the iteration are avoided and all existing
sites are fixed in one go.

Expand the lock held sections so both operations are covered and the bitmap
and the radixtree are in sync.

Fixes: a05a900a51c7 ("genirq: Make sparse_lock a mutex")
Reported-and-tested-by: Huang Ying <ying.huang@intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
Acked-by: Michal Suchanek <msuchanek@suse.de>
---
 kernel/irq/irqdesc.c | 24 +++++++-----------------
 1 file changed, 7 insertions(+), 17 deletions(-)

diff --git a/kernel/irq/irqdesc.c b/kernel/irq/irqdesc.c
index 00bb0aeea1d0..77977f55dff7 100644
--- a/kernel/irq/irqdesc.c
+++ b/kernel/irq/irqdesc.c
@@ -405,10 +405,8 @@ static void free_desc(unsigned int irq)
 	 * The sysfs entry must be serialized against a concurrent
 	 * irq_sysfs_init() as well.
 	 */
-	mutex_lock(&sparse_irq_lock);
 	kobject_del(&desc->kobj);
 	delete_irq_desc(irq);
-	mutex_unlock(&sparse_irq_lock);
 
 	/*
 	 * We free the descriptor, masks and stat fields via RCU. That
@@ -446,20 +444,15 @@ static int alloc_descs(unsigned int start, unsigned int cnt, int node,
 		desc = alloc_desc(start + i, node, flags, mask, owner);
 		if (!desc)
 			goto err;
-		mutex_lock(&sparse_irq_lock);
 		irq_insert_desc(start + i, desc);
 		irq_sysfs_add(start + i, desc);
-		mutex_unlock(&sparse_irq_lock);
 	}
+	bitmap_set(allocated_irqs, start, cnt);
 	return start;
 
 err:
 	for (i--; i >= 0; i--)
 		free_desc(start + i);
-
-	mutex_lock(&sparse_irq_lock);
-	bitmap_clear(allocated_irqs, start, cnt);
-	mutex_unlock(&sparse_irq_lock);
 	return -ENOMEM;
 }
 
@@ -558,6 +551,7 @@ static inline int alloc_descs(unsigned int start, unsigned int cnt, int node,
 
 		desc->owner = owner;
 	}
+	bitmap_set(allocated_irqs, start, cnt);
 	return start;
 }
 
@@ -653,10 +647,10 @@ void irq_free_descs(unsigned int from, unsigned int cnt)
 	if (from >= nr_irqs || (from + cnt) > nr_irqs)
 		return;
 
+	mutex_lock(&sparse_irq_lock);
 	for (i = 0; i < cnt; i++)
 		free_desc(from + i);
 
-	mutex_lock(&sparse_irq_lock);
 	bitmap_clear(allocated_irqs, from, cnt);
 	mutex_unlock(&sparse_irq_lock);
 }
@@ -703,19 +697,15 @@ __irq_alloc_descs(int irq, unsigned int from, unsigned int cnt, int node,
 					   from, cnt, 0);
 	ret = -EEXIST;
 	if (irq >=0 && start != irq)
-		goto err;
+		goto unlock;
 
 	if (start + cnt > nr_irqs) {
 		ret = irq_expand_nr_irqs(start + cnt);
 		if (ret)
-			goto err;
+			goto unlock;
 	}
-
-	bitmap_set(allocated_irqs, start, cnt);
-	mutex_unlock(&sparse_irq_lock);
-	return alloc_descs(start, cnt, node, affinity, owner);
-
-err:
+	ret = alloc_descs(start, cnt, node, affinity, owner);
+unlock:
 	mutex_unlock(&sparse_irq_lock);
 	return ret;
 }
-- 
2.13.6