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[PATCH] kernel/resource.c: ensure parent is not freed in __request_region()

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The commit 59ceeaaf355fa0fb16558ef7c24413c804932ada
("kernel/resource.c: fix muxed resource handling in __request_region()")
don't address properly the case where the current parent resource has
been freed while sleeping, waiting for a muxed resource to be available.

This patch fixes the issue by resetting the parent pointer to the root
parent resource when sleeping is needed.

Signed-off-by: Simon Guinot <simon.guinot@sequanux.org>
Cc: stable@vger.kernel.org
---
 kernel/resource.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/kernel/resource.c b/kernel/resource.c
index 3669d1bfc425..14a7f9d66259 100644
--- a/kernel/resource.c
+++ b/kernel/resource.c
@@ -1052,16 +1052,17 @@ static DECLARE_WAIT_QUEUE_HEAD(muxed_resource_wait);
 
 /**
  * __request_region - create a new busy resource region
- * @parent: parent resource descriptor
+ * @root: root resource descriptor
  * @start: resource start address
  * @n: resource region size
  * @name: reserving caller's ID string
  * @flags: IO resource flags
  */
-struct resource * __request_region(struct resource *parent,
+struct resource * __request_region(struct resource *root,
 				   resource_size_t start, resource_size_t n,
 				   const char *name, int flags)
 {
+	struct resource *parent = root;
 	DECLARE_WAITQUEUE(wait, current);
 	struct resource *res = alloc_resource(GFP_KERNEL);
 
@@ -1089,6 +1090,7 @@ struct resource * __request_region(struct resource *parent,
 			}
 		}
 		if (conflict->flags & flags & IORESOURCE_MUXED) {
+			parent = root;
 			add_wait_queue(&muxed_resource_wait, &wait);
 			write_unlock(&resource_lock);
 			set_current_state(TASK_UNINTERRUPTIBLE);
-- 
2.1.4

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Re: [PATCH] kernel/resource.c: fix muxed resource handling in  __request_region() Simon Guinot <simon.guinot@sequanux.org> - 2016-02-23 17:20 +0100
  Re: [PATCH] kernel/resource.c: fix muxed resource handling in  __request_region() Jesse Barnes <jbarnes@virtuousgeek.org> - 2016-02-23 18:20 +0100
    Re: [PATCH] kernel/resource.c: fix muxed resource handling in  __request_region() One Thousand Gnomes <gnomes@lxorguk.ukuu.org.uk> - 2016-02-23 22:40 +0100
    [PATCH] kernel/resource.c: ensure parent is not freed in __request_region() Simon Guinot <simon.guinot@sequanux.org> - 2016-02-24 15:30 +0100

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