Re: [PATCH v4] bitops: Fix shift overflow in GENMASK macros

[Andrew Morton]

On Thu,  6 Nov 2014 10:54:19 +0100 Maxime COQUELIN <maxime.coquelin@xxxxxx> wrote:

> On some 32 bits architectures, including x86, GENMASK(31, 0) returns 0
> instead of the expected ~0UL.
> 
> This is the same on some 64 bits architectures with GENMASK_ULL(63, 0).
> 
> This is due to an overflow in the shift operand, 1 << 32 for GENMASK,
> 1 << 64 for GENMASK_ULL.
> 
> Fixes: 10ef6b0dffe404bcc54e94cb2ca1a5b18445a66b
> Cc: <stable@xxxxxxxxxxxxxxx> #v3.13+
> Reported-by: Eric Paire <eric.paire@xxxxxx>
> Suggested-by: Rasmus Villemoes <linux@xxxxxxxxxxxxxxxxxx>
> Signed-off-by: Maxime Coquelin <maxime.coquelin@xxxxxx>

Why cc:stable?  Does this bug cause some observed kernel misbehaviour? 
If so, please fully describe that in the changelog.  This will help
people to determine whether this patch might fix a bug they're
observing, and will help them to decide whether they should backport
this patch into their kernels.

I'm assuming that Peter will be merging this patch.

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