Patch "xen/balloon: Fix crash when ballooning on x86 32 bit PAE" has been added to the 4.5-stable tree

This is a note to let you know that I've just added the patch titled

xen/balloon: Fix crash when ballooning on x86 32 bit PAE

to the 4.5-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
xen-balloon-fix-crash-when-ballooning-on-x86-32-bit-pae.patch
and it can be found in the queue-4.5 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Ross Lagerwall <[email protected]>
Date: Thu, 17 Mar 2016 16:52:00 +0000
Subject: xen/balloon: Fix crash when ballooning on x86 32 bit PAE

From: Ross Lagerwall <[email protected]>

commit dfd74a1edfaba5864276a2859190a8d242d18952 upstream.

Commit 55b3da98a40dbb3776f7454daf0d95dde25c33d2 (xen/balloon: find non-conflicting regions to place hotplugged memory) caused a regression in 4.4.

When ballooning on an x86 32 bit PAE system with close to 64 GiB of memory, the address returned by allocate_resource may be above 64 GiB. When using CONFIG_SPARSEMEM, this setup is limited to using physical addresses < 64 GiB. When adding memory at this address, it runs off the end of the mem_section array and causes a crash. Instead, fail the ballooning request.

---
 drivers/xen/balloon.c |   16 ++++++++++++++++
 1 file changed, 16 insertions(+)

@@ -152,6 +152,8 @@ static DECLARE_WAIT_QUEUE_HEAD(balloon_w
 static void balloon_process(struct work_struct *work);
 static DECLARE_DELAYED_WORK(balloon_worker, balloon_process);
 
+static void release_memory_resource(struct resource *resource);
+
 /* When ballooning out (allocating memory to return to Xen) we don't really
    want the kernel to try too hard since that can trigger the oom killer. */
 #define GFP_BALLOON \

@@ -268,6 +270,20 @@ static struct resource *additional_memor
 		return NULL;
 	}
 
+#ifdef CONFIG_SPARSEMEM
+	{
+		unsigned long limit = 1UL << (MAX_PHYSMEM_BITS - PAGE_SHIFT);
+		unsigned long pfn = res->start >> PAGE_SHIFT;
+
+		if (pfn > limit) {
+			pr_err("New System RAM resource outside addressable RAM (%lu > %lu)\n",
+			       pfn, limit);
+			release_memory_resource(res);
+			return NULL;
+		}
+	}
+#endif
+
 	return res;
 }
 

Patches currently in stable-queue which might be from [email protected] are

queue-4.5/xen-balloon-fix-crash-when-ballooning-on-x86-32-bit-pae.patch queue-4.5/xen-fix-page-pfn-conversion-on-32-bit-systems.patch