netdev - Re: [PATCH v2] rps: fix insufficient bounds checking in store_rps_dev_flow_table

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Message-Id: <C6E2C6E1-A4DA-45F8-A94F-D3B78AFA018F@gmail.com>
Date:	Fri, 23 Dec 2011 10:07:57 -0500
From:	Xi Wang <xi.wang@...il.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	Tom Herbert <therbert@...gle.com>,
	"David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org
Subject: Re: [PATCH v2] rps: fix insufficient bounds checking in store_rps_dev_flow_table_cnt()

On Dec 23, 2011, at 9:53 AM, Eric Dumazet wrote:
> Unsigned arithmetics is well defined in C. Very well in fact.

Oversized shifts are undefined in C, no matter it is unsigned
or not; roundup_pow_of_two() is implemented by shifting.

>> BTW, (count > UINT_MAX) is shorter and easier to understand
>> than (count != (unsigned long)(u32)count).
> 
> You miss the point. UINT_MAX is too small for 64bit arches.

I am sorry why is it too small?  what's difference between
(count > UINT_MAX) and (count != (unsigned long)(u32)count)?

- xi
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