linux-kernel - Re: [PATCH 2/2] MIPS: o32: Get rid of useless wrapper for llseek

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Date:	Wed, 25 Mar 2009 13:28:29 -0600
From:	dann frazier <dannf@...ian.org>
To:	Heiko Carstens <heiko.carstens@...ibm.com>
Cc:	Ralf Baechle <ralf@...ux-mips.org>, linux-arch@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-mips@...ux-mips.org
Subject: Re: [PATCH 2/2] MIPS: o32: Get rid of useless wrapper for llseek

On Wed, Mar 25, 2009 at 06:29:05PM +0100, Heiko Carstens wrote:
> On Wed, 25 Mar 2009 01:15:55 +0100
> Ralf Baechle <ralf@...ux-mips.org> wrote:
> 
> > Signed-off-by: Ralf Baechle <ralf@...ux-mips.org>
> > 
> >  arch/mips/kernel/linux32.c     |    7 -------
> >  arch/mips/kernel/scall64-o32.S |    2 +-
> >  2 files changed, 1 insertions(+), 8 deletions(-)
> > 
> > diff --git a/arch/mips/kernel/linux32.c b/arch/mips/kernel/linux32.c
> > index 49aac6e..ab2da41 100644
> > --- a/arch/mips/kernel/linux32.c
> > +++ b/arch/mips/kernel/linux32.c
> > @@ -133,13 +133,6 @@ SYSCALL_DEFINE4(32_ftruncate64, unsigned long, fd, unsigned long, __dummy,
> >  	return sys_ftruncate(fd, merge_64(a2, a3));
> >  }
> > 
> > -SYSCALL_DEFINE5(32_llseek, unsigned long, fd, unsigned long, offset_high,
> > -	unsigned long, offset_low, loff_t __user *, result,
> > -	unsigned long, origin)
> > -{
> > -	return sys_llseek(fd, offset_high, offset_low, result, origin);
> > -}
> > -
> 
> Ah.. this hunk seems to be the origin of the bug. git commit
> dbda6ac0897603f6c6dfadbbc37f9882177ec7ac "MIPS: CVE-2009-0029: Enable
> syscall wrappers." contains this:
> 
> -asmlinkage int sys32_llseek(unsigned int fd, unsigned int offset_high,
> -			    unsigned int offset_low, loff_t __user * result,
> -			    unsigned int origin)
> +SYSCALL_DEFINE5(32_llseek, unsigned long, fd, unsigned long, offset_high,
> +	unsigned long, offset_low, loff_t __user *, result,
> +	unsigned long, origin)
> 
> Here you converted offset_low from unsigned int to unsigned long. Hence
> you lost the clearing of the upper 32 bits. That would explain the bug.
> Any chance the process where the bug was seen was a compat process?

$ file /sbin/e2fsck 
/sbin/e2fsck: ELF 32-bit MSB executable, MIPS, MIPS-I version 1 (SYSV), dynamically linked (uses shared libs), for GNU/Linux 2.6.8, with unknown capability 0x41000000 = 0xf676e75, stripped

> Patch below would probably fix it.

This patch works for me on the aforementioned Debian system.

> Btw. there are a lot of int->long conversions in the git commit
> mentioned above. AFAICS all(?) of the conversions are wrong.

> diff --git a/arch/mips/kernel/linux32.c b/arch/mips/kernel/linux32.c
> index 1a86f84..5abcc7f 100644
> --- a/arch/mips/kernel/linux32.c
> +++ b/arch/mips/kernel/linux32.c
> @@ -134,9 +134,9 @@ SYSCALL_DEFINE4(32_ftruncate64, unsigned long, fd, unsigned long, __dummy,
>  	return sys_ftruncate(fd, merge_64(a2, a3));
>  }
>  
> -SYSCALL_DEFINE5(32_llseek, unsigned long, fd, unsigned long, offset_high,
> -	unsigned long, offset_low, loff_t __user *, result,
> -	unsigned long, origin)
> +SYSCALL_DEFINE5(32_llseek, unsigned int, fd, unsigned int, offset_high,
> +		unsigned int, offset_low, loff_t __user *, result,
> +		unsigned int, origin)
>  {
>  	return sys_llseek(fd, offset_high, offset_low, result, origin);
>  }
> 

-- 
dann frazier

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