linux-kernel - Re: [PATCH] staging: tidspbridge: fix signess error

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Message-ID: <20101012164815.GA28276@albatros>
Date:	Tue, 12 Oct 2010 20:48:15 +0400
From:	Vasiliy Kulikov <segooon@...il.com>
To:	Dan Rosenberg <drosenberg@...curity.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] staging: tidspbridge: fix signess error

On Mon, Oct 11, 2010 at 16:24 -0400, Dan Rosenberg wrote:
> It seems to me that in a lot of cases, signed types were used initially
> with checks that the value was not below zero, but then unsigned types
> were substituted due to problems later on (potentially security
> related), and the checks were never removed.  Just because a check
> doesn't make sense doesn't necessarily mean it's safe to revert an
> unsigned type to a signed one - just be careful to make sure you're not
> introducing any problems when you make these kinds of changes.  I have
> no idea whether or not this is the case in this particular example.

i is used as the store for get_user_pages() result, which may be
-EFAULT.

> > i was unsigned, so check for (i < 0) made no sense.  Made it signed.
> > 
> > Signed-off-by: Vasiliy Kulikov <segooon@...il.com>
> > ---
> >  I cannot compile this driver, so it is not tested.
> >  drivers/staging/tidspbridge/core/dsp-mmu.c |    3 ++-
> >  1 files changed, 2 insertions(+), 1 deletions(-)
> > diff --git a/drivers/staging/tidspbridge/core/dsp-mmu.c b/drivers/staging/tidspbridge/core/dsp-mmu.c
> > index 3c978f9..983c95a 100644
> > --- a/drivers/staging/tidspbridge/core/dsp-mmu.c
> > +++ b/drivers/staging/tidspbridge/core/dsp-mmu.c
> > @@ -219,7 +219,8 @@ u32 user_to_dsp_map(struct iommu *mmu, u32 uva, u32 da, u32 size,
> >  				struct page **usr_pgs)
> >  {
> >  	int res, w;
> > -	unsigned pages, i;
> > +	unsigned pages;
> > +	int i;
> >  	struct vm_area_struct *vma;
> >  	struct mm_struct *mm = current->mm;
> >  	struct sg_table *sgt;
> > -- 
> > 1.7.0.4
> 
> 

-- 
Vasiliy
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