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

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Message-Id: <20111222.223738.869939610976955478.davem@davemloft.net>
Date:	Thu, 22 Dec 2011 22:37:38 -0500 (EST)
From:	David Miller <davem@...emloft.net>
To:	xi.wang@...il.com
Cc:	eric.dumazet@...il.com, therbert@...gle.com, netdev@...r.kernel.org
Subject: Re: [PATCH v2] rps: fix insufficient bounds checking in
 store_rps_dev_flow_table_cnt()

From: Xi Wang <xi.wang@...il.com>
Date: Thu, 22 Dec 2011 18:35:22 -0500

> Setting a large rps_flow_cnt like (1 << 30) on 32-bit platform will
> cause a kernel oops due to insufficient bounds checking.
> 
> 	if (count > 1<<30) {
> 		/* Enforce a limit to prevent overflow */
> 		return -EINVAL;
> 	}
> 	count = roundup_pow_of_two(count);
> 	table = vmalloc(RPS_DEV_FLOW_TABLE_SIZE(count));
> 
> Note that the macro RPS_DEV_FLOW_TABLE_SIZE(count) is defined as:
> 
> 	... + (count * sizeof(struct rps_dev_flow))
> 
> where sizeof(struct rps_dev_flow) is 8.  (1 << 30) * 8 will overflow
> 32 bits.
> 
> This patch replaces the magic number (1 << 30) with a symbolic bound.
> 
> Suggested-by: Eric Dumazet <eric.dumazet@...il.com>
> Signed-off-by: Xi Wang <xi.wang@...il.com>

Applied.
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