linux-ext4 - Re: [PATCH] Fix oops in mballoc caused by a variable overflow

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Message-ID: <20080117120752.GB24979@skywalker>
Date:	Thu, 17 Jan 2008 17:37:52 +0530
From:	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
To:	Valerie Clement <valerie.clement@...l.net>
Cc:	Mingming Cao <cmm@...ibm.com>,
	linux-ext4 <linux-ext4@...r.kernel.org>
Subject: Re: [PATCH] Fix oops in mballoc caused by a variable overflow

On Thu, Jan 17, 2008 at 10:43:40AM +0100, Valerie Clement wrote:
> Aneesh Kumar K.V wrote:
>> What about this  ? I guess we will overflow start = start << bsbits;
>>
>
> Hi Aneesh,
> your patch below doesn't fix the issue, because as start_off is also  
> loff_t, start_off = ac->ac_o_ex.fe_logical << bsbits  also overflows.
>

loff_t is 64 bits.

typedef __kernel_loff_t         loff_t;
typedef long long       __kernel_loff_t;
typedef __u32 ext4_lblk_t;
typedef unsigned long long ext4_fsblk_t

start_off = ac->ac_o_ex.fe_logical << bsbits;

In the above line what we are storing in start_off is the offset in bytes.So it makes
sense to use the type loff_t. It is neither logical block nor physical block.


-aneesh
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