Commit 91d86314 authored Aug 28, 2014 by Greg Hackmann Committed by Dmitry Shmidt Jan 27, 2017

ANDROID: arm64: check for upper PAGE_SHIFT bits in pfn_valid()



pfn_valid() returns a false positive when the lower (64 - PAGE_SHIFT)
bits match a valid pfn but some of the upper bits are set.  This caused
a kernel panic in kpageflags_read() when a userspace utility parsed
/proc/*/pagemap, neglected to discard the upper flag bits, and tried to
lseek()+read() from the corresponding offset in /proc/kpageflags.

A valid pfn will never have the upper PAGE_SHIFT bits set, so simply
check for this before passing the pfn to memblock_is_memory().

Change-Id: Ief5d8cd4dd93cbecd545a634a8d5885865cb5970
Signed-off-by: Greg Hackmann <ghackmann@google.com>

parent f556868a

arch/arm64/mm/init.c

+3 −1

Original line number	Diff line number	Diff line
		@@ -145,9 +145,11 @@ static void __init zone_sizes_init(unsigned long min, unsigned long max)
		#endif /* CONFIG_NUMA */

		#ifdef CONFIG_HAVE_ARCH_PFN_VALID
		#define PFN_MASK ((1UL << (64 - PAGE_SHIFT)) - 1)

		int pfn_valid(unsigned long pfn)
		{
		return memblock_is_map_memory(pfn << PAGE_SHIFT);
		return (pfn & PFN_MASK) == pfn && memblock_is_map_memory(pfn << PAGE_SHIFT);
		}
		EXPORT_SYMBOL(pfn_valid);
		#endif