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While the DOC at the beginning of lib/bitmap.c explicitly states that
"The number of valid bits in a given bitmap does _not_ need to be an
exact multiple of BITS_PER_LONG.", some of the bitmap operations do
indeed access BITS_PER_LONG portions of the provided bitmap no matter
the size of the provided bitmap. For example, if bitmap_intersects()
is provided with an 8 bit bitmap the operation will access
BITS_PER_LONG bits from the provided bitmap. While the operation
ensures that these extra bits do not affect the result, the memory
is still accessed.
The capacity bitmasks (CBMs) are typically stored in u32 since they
can never exceed 32 bits. A few instances exist where a bitmap_*
operation is performed on a CBM by simply pointing the bitmap operation
to the stored u32 value.
The consequence of this pattern is that some bitmap_* operations will
access out-of-bounds memory when interacting with the provided CBM. This
is confirmed with a KASAN test that reports:
BUG: KASAN: stack-out-of-bounds in __bitmap_intersects+0xa2/0x100
and
BUG: KASAN: stack-out-of-bounds in __bitmap_weight+0x58/0x90
Fix this by moving any CBM provided to a bitmap operation needing
BITS_PER_LONG to an 'unsigned long' variable.
[ tglx: Changed related function arguments to unsigned long and got rid
of the _cbm extra step ]
Fixes: 72d5050566 ("x86/intel_rdt: Add utilities to test pseudo-locked region possibility")
Fixes: 49f7b4efa1 ("x86/intel_rdt: Enable setting of exclusive mode")
Fixes: d9b48c86eb ("x86/intel_rdt: Display resource groups' allocations' size in bytes")
Fixes: 95f0b77efa ("x86/intel_rdt: Initialize new resource group with sane defaults")
Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: fenghua.yu@intel.com
Cc: tony.luck@intel.com
Cc: gavin.hindman@intel.com
Cc: jithu.joseph@intel.com
Cc: dave.hansen@intel.com
Cc: hpa@zytor.com
Link: https://lkml.kernel.org/r/69a428613a53f10e80594679ac726246020ff94f.1538686926.git.reinette.chatre@intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
49e00eee00