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>
diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
index 212c4d1..af38d02 100644
--- a/arch/arm64/mm/init.c
+++ b/arch/arm64/mm/init.c
@@ -145,9 +145,11 @@
#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