| From | Greg Kroah-Hartman <> | Subject | [PATCH 4.5 46/88] xen/balloon: Fix crash when ballooning on x86 32 bit PAE | Date | Mon, 9 May 2016 09:21:35 +0200 |
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4.5-stable review patch. If anyone has any objections, please let me know.
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From: Ross Lagerwall <ross.lagerwall@citrix.com>
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>
--- drivers/xen/balloon.c | 16 ++++++++++++++++ 1 file changed, 16 insertions(+)
--- a/drivers/xen/balloon.c +++ b/drivers/xen/balloon.c @@ -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; }
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