Commit 5a049f14 authored Nov 18, 2013 by Anton Blanchard Committed by Benjamin Herrenschmidt Nov 21, 2013

powerpc: ppc64 address space capped at 32TB, mmap randomisation disabled



Commit fba2369e (mm: use vm_unmapped_area() on powerpc architecture)
has a bug in slice_scan_available() where we compare an unsigned long
(high_slices) against a shifted int. As a result, comparisons against
the top 32 bits of high_slices (representing the top 32TB) always
returns 0 and the top of our mmap region is clamped at 32TB

This also breaks mmap randomisation since the randomised address is
always up near the top of the address space and it gets clamped down
to 32TB.

Cc: stable@vger.kernel.org # v3.10+
Signed-off-by: Anton Blanchard <anton@samba.org>
Acked-by: Michel Lespinasse <walken@google.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

parent 6d888d1a

arch/powerpc/mm/slice.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -258,7 +258,7 @@ static bool slice_scan_available(unsigned long addr,
		slice = GET_HIGH_SLICE_INDEX(addr);
		*boundary_addr = (slice + end) ?
		((slice + end) << SLICE_HIGH_SHIFT) : SLICE_LOW_TOP;
		return !!(available.high_slices & (1u << slice));
		return !!(available.high_slices & (1ul << slice));
		}
		}

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