xen/balloon: Fix crash when ballooning on x86 32 bit PAE
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.
Signed-off-by: Ross Lagerwall <ross.lagerwall@citrix.com>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c
index 12eab50..364bc44 100644
--- a/drivers/xen/balloon.c
+++ b/drivers/xen/balloon.c
@@ -152,6 +152,8 @@
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 @@
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;
}
