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

Commit 55b3da98a4 (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>
Cc: <stable@vger.kernel.org> # 4.4+
Signed-off-by: David Vrabel <david.vrabel@citrix.com>
This commit is contained in:
Ross Lagerwall 2016-03-17 16:52:00 +00:00 committed by David Vrabel
parent 60901df3ae
commit dfd74a1edf
1 changed files with 16 additions and 0 deletions
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16
drivers/xen/balloon.c
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@ -151,6 +151,8 @@ 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 \
@ -267,6 +269,20 @@ static struct resource *additional_memory_resource(phys_addr_t size)
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;
}