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

Commit fba2369e6c (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>
This commit is contained in:
Anton Blanchard 2013-11-18 14:55:28 +11:00 committed by Benjamin Herrenschmidt
parent 6d888d1ab0
commit 5a049f1490
1 changed files with 1 additions and 1 deletions
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arch/powerpc/mm/slice.c
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@ -258,7 +258,7 @@ static bool slice_scan_available(unsigned long addr,
slice = GET_HIGH_SLICE_INDEX(addr); slice = GET_HIGH_SLICE_INDEX(addr);
*boundary_addr = (slice + end) ? *boundary_addr = (slice + end) ?
((slice + end) << SLICE_HIGH_SHIFT) : SLICE_LOW_TOP; ((slice + end) << SLICE_HIGH_SHIFT) : SLICE_LOW_TOP;
return !!(available.high_slices & (1u << slice)); return !!(available.high_slices & (1ul << slice));
} }
} }