linux-kernel - Re: [PATCH] scsi: int overflow in st

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Message-ID: <CAAdffVH3pPpvu+GWwikPpGynTRRMW2unbyRvP2jQWpUU-=R6qw@mail.gmail.com>
Date:	Wed, 18 Dec 2013 12:00:20 +0800
From:	Yu Chen <chyyuu@...il.com>
To:	Kai Mäkisara (Kolumbus) 
	<kai.makisara@...umbus.fi>
Cc:	徐永健 <xuyongjiande@...il.com>,
	"James E.J. Bottomley" <JBottomley@...allels.com>,
	linux-kernel@...r.kernel.org, linux-scsi@...r.kernel.org
Subject: Re: [PATCH] scsi: int overflow in st_ioctl()

Because the local variable of st_int_ioctl function, such as long ltmp
be assigned by arg.
I think  we should limit the parameter arg of st_int_ioctl function to
the range of 24-bit signed integer.
Yong Jianxu, please update your patch.

2013/12/18 "Kai Mäkisara (Kolumbus)" <kai.makisara@...umbus.fi>:
> On 17.12.2013, at 16.43, Yongjian Xu xuyongjiande@...il.com wrote:
>
>> From: Yongjian Xu <xuyongjiande@...il.com>
>>
>> mtc.mt_count comes from user-space.
>> int overflow may occur:
>> mtc.mt_count++;
>> mtc.mt_count—;
>
> I agree that this is a problem. However, it seems that there is also another problem: the SPACE command uses a 24-bit count field and this overflows far below INT_MAX. Should the count in MTFSF etc. be limited to (2<<24-2)? This would make the checks you suggest unnecessary. (-2 so that the behavior does not depend on whether we are at file mark or not.)
>
> I am a bit hesitant with this suggestion because someone may use count INT_MAX to space to the end of the tape. This probably succeeds now but after the fix it would return an error.
>
> Thanks,
> Kai
>
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-- 
Best Regards
==============================================
Yu Chen
Ph.D.  Associate Professor
System Software&Software Engineering Group,
Dept. of Computer Science and Technology
Tsinghua University, Beijing 100084, P.R. China
E-Mail: mailto:yuchen@...nghua.edu.cn  chyyuu@...il.com
==============================================
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