RE: [PATCH] x86/resctrl: Prevent possible overrun during bitmap operations
From: David Laight
Date: Mon Jun 24 2019 - 09:55:13 EST
From: Reinette Chatre
> Sent: 19 June 2019 21:27
> 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 find_first_bit()
> 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.
I suspect that comment also needs correcting.
On BE systems you really do need to have a array of longs.
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