From dfd74a1edfaba5864276a2859190a8d242d18952 Mon Sep 17 00:00:00 2001 From: Ross Lagerwall Date: Thu, 17 Mar 2016 16:52:00 +0000 Subject: [PATCH] xen/balloon: Fix crash when ballooning on x86 32 bit PAE 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 Cc: # 4.4+ Signed-off-by: David Vrabel --- drivers/xen/balloon.c | 16 ++++++++++++++++ 1 file changed, 16 insertions(+) diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c index 9781e0dd59d6..d46839f51e73 100644 --- a/drivers/xen/balloon.c +++ b/drivers/xen/balloon.c @@ -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; }