linux-kernel - Re: [ 137/143] xfs: underflow bug in xfs_attrlist_by

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Date:	Tue, 13 May 2014 12:08:12 +0100
From:	Luis Henriques <luis.henriques@...onical.com>
To:	Willy Tarreau <w@....eu>
Cc:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	Dan Carpenter <dan.carpenter@...cle.com>,
	Ben Myers <bpm@....com>
Subject: Re: [ 137/143] xfs: underflow bug in xfs_attrlist_by_handle()

On Mon, May 12, 2014 at 02:34:17AM +0200, Willy Tarreau wrote:
> 2.6.32-longterm review patch.  If anyone has any objections, please let me know.
> 
> ------------------
> 
> From: Dan Carpenter <dan.carpenter@...cle.com>
> 
> If we allocate less than sizeof(struct attrlist) then we end up
> corrupting memory or doing a ZERO_PTR_SIZE dereference.
> 
> This can only be triggered with CAP_SYS_ADMIN.
> 
> Reported-by: Nico Golde <nico@...lde.de>
> Reported-by: Fabian Yamaguchi <fabs@...sec.de>
> Signed-off-by: Dan Carpenter <dan.carpenter@...cle.com>
> Reviewed-by: Dave Chinner <dchinner@...hat.com>
> Signed-off-by: Ben Myers <bpm@....com>
> 
> (cherry picked from commit 071c529eb672648ee8ca3f90944bcbcc730b4c06)
> [dannf: backported to Debian's 2.6.32]
> Signed-off-by: Willy Tarreau <w@....eu>
> ---
>  fs/xfs/linux-2.6/xfs_ioctl.c   | 3 ++-
>  fs/xfs/linux-2.6/xfs_ioctl32.c | 4 ++--
>  2 files changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/xfs/linux-2.6/xfs_ioctl.c b/fs/xfs/linux-2.6/xfs_ioctl.c
> index 942362f..5663351 100644
> --- a/fs/xfs/linux-2.6/xfs_ioctl.c
> +++ b/fs/xfs/linux-2.6/xfs_ioctl.c
> @@ -410,7 +410,8 @@ xfs_attrlist_by_handle(
>  		return -XFS_ERROR(EPERM);
>  	if (copy_from_user(&al_hreq, arg, sizeof(xfs_fsop_attrlist_handlereq_t)))
>  		return -XFS_ERROR(EFAULT);
> -	if (al_hreq.buflen > XATTR_LIST_MAX)
> +	if (al_hreq.buflen < sizeof(struct attrlist) ||
> +	    al_hreq.buflen > XATTR_LIST_MAX)
>  		return -XFS_ERROR(EINVAL);
>  
>  	/*
> diff --git a/fs/xfs/linux-2.6/xfs_ioctl32.c b/fs/xfs/linux-2.6/xfs_ioctl32.c
> index bad485a..782d03d 100644
> --- a/fs/xfs/linux-2.6/xfs_ioctl32.c
> +++ b/fs/xfs/linux-2.6/xfs_ioctl32.c
> @@ -361,8 +361,8 @@ xfs_compat_attrlist_by_handle(
>  	if (copy_from_user(&al_hreq, arg,
>  			   sizeof(compat_xfs_fsop_attrlist_handlereq_t)))
>  		return -XFS_ERROR(EFAULT);
> -	if (al_hreq.buflen > XATTR_LIST_MAX)
> -		return -XFS_ERROR(EINVAL);

Am I missing something or was the above return statement deleted by
mistake?

Cheers,
--
Luís

> +	if (al_hreq.buflen < sizeof(struct attrlist) ||
> +	    al_hreq.buflen > XATTR_LIST_MAX)
>  
>  	/*
>  	 * Reject flags, only allow namespaces.
> -- 
> 1.7.12.2.21.g234cd45.dirty
> 
> 
> 
> --
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