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arm64: check for upper PAGE_SHIFT bits in pfn_valid()

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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>
This commit is contained in:
Greg Hackmann 2014-08-28 14:00:10 -07:00 • committed by John Stultz
parent 487e34bfed
commit c6a9c8e51b
1 changed files with 3 additions and 1 deletions
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4
arch/arm64/mm/init.c
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@ -118,9 +118,11 @@ static void __init zone_sizes_init(unsigned long min, unsigned long max)
}
#ifdef CONFIG_HAVE_ARCH_PFN_VALID
#define PFN_MASK ((1UL << (64 - PAGE_SHIFT)) - 1)
int pfn_valid(unsigned long pfn)
{
return memblock_is_memory(pfn << PAGE_SHIFT);
return (pfn & PFN_MASK) == pfn && memblock_is_memory(pfn << PAGE_SHIFT);
}
EXPORT_SYMBOL(pfn_valid);
#endif