linux-kernel - Re: [SCSI] compat_ioct: fix bsg SG

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Message-ID: <20111102092414.GE4751@mwanda>
Date:	Wed, 2 Nov 2011 12:24:14 +0300
From:	Dan Carpenter <dan.carpenter@...cle.com>
To:	James Bottomley <James.Bottomley@...senPartnership.com>
Cc:	FUJITA Tomonori <fujita.tomonori@....ntt.co.jp>,
	Giridhar Malavali <giridhar.malavali@...gic.com>,
	linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [SCSI] compat_ioct: fix bsg SG_IO

On Wed, Nov 02, 2011 at 12:58:58PM +0400, James Bottomley wrote:
> On Wed, 2011-11-02 at 11:16 +0300, Dan Carpenter wrote:
> > 84eb8fb42c120 "[SCSI] compat_ioct: fix bsg SG_IO" introduces an
> > uninitialized variable use.
> > 
> >    278  static int sg_ioctl_trans(unsigned int fd, unsigned int cmd,
> >    279                          sg_io_hdr32_t __user *sgio32)
> >    280  {
> >    281          sg_io_hdr_t __user *sgio;
> >    282          u16 iovec_count;
> >    283          u32 data;
> >    284          void __user *dxferp;
> >    285          int err;
> >    286          int interface_id;
> >    287  
> >    288          if (get_user(interface_id, &sgio32->interface_id))
> >                                             ^^^^^^
> > sgio32 is unitialized here.  Unfortunately Gcc doesn't warn about it.
> 
> I don't quite understand what makes you think that: it's passed in as an
> argument to the function.  It's a pointer to the userspace 32 bit
> representation of the structure.  The use logic is a slightly convoluted
> way of saying we only understand the 'S' header but we're going to let
> the real ioctl routine say what the error is if it's not type 'S'.

Uh...  This is embarrassing.  I got confused between sgio and sgio32.

Sorry for this.

regards,
dan carpenter

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