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From: Ross Lagerwall <ross.lagerwall@citrix.com>
To: xen-devel@lists.xenproject.org
Cc: Ross Lagerwall <ross.lagerwall@citrix.com>,
	Boris Ostrovsky <boris.ostrovsky@oracle.com>,
	David Vrabel <david.vrabel@citrix.com>
Subject: [PATCH 2/2] xen/balloon: Fix crash when ballooning on x86 32 bit PAE
Date: Thu, 17 Mar 2016 16:52:00 +0000	[thread overview]
Message-ID: <1458233520-18821-2-git-send-email-ross.lagerwall@citrix.com> (raw)
In-Reply-To: <1458233520-18821-1-git-send-email-ross.lagerwall@citrix.com>

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.

Signed-off-by: Ross Lagerwall <ross.lagerwall@citrix.com>
 drivers/xen/balloon.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c
index 12eab50..329695d 100644
--- a/drivers/xen/balloon.c
+++ b/drivers/xen/balloon.c
@@ -152,6 +152,8 @@ static DECLARE_WAIT_QUEUE_HEAD(balloon_wq);
 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 +270,19 @@ static struct resource *additional_memory_resource(phys_addr_t size)
 		return NULL;
+	{
+		unsigned long max_pfn = 1UL << (MAX_PHYSMEM_BITS - PAGE_SHIFT);
+		unsigned long pfn = res->start >> PAGE_SHIFT;
+		if (pfn > max_pfn) {
+			pr_err("pfn %lu exceeds max_pfn %lu\n", pfn, max_pfn);
+			release_memory_resource(res);
+			return NULL;
+		}
+	}
 	return res;

Xen-devel mailing list

  reply	other threads:[~2016-03-17 16:52 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-03-17 16:51 [PATCH 1/2] xen: Fix page <-> pfn conversion on 32 bit systems Ross Lagerwall
2016-03-17 16:52 ` Ross Lagerwall [this message]
2016-04-06 12:48   ` [PATCH 2/2] xen/balloon: Fix crash when ballooning on x86 32 bit PAE David Vrabel

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