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Re: [PATCH v4 3/7] xfs: ioctl check for capabilities in the current user

To: Dwight Engen <dwight.engen@xxxxxxxxxx>
Subject: Re: [PATCH v4 3/7] xfs: ioctl check for capabilities in the current user namespace
From: Dave Chinner <david@xxxxxxxxxxxxx>
Date: Fri, 19 Jul 2013 15:29:20 +1000
Cc: xfs@xxxxxxxxxxx
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <20130717114727.23491330@xxxxxxxxxx>
References: <20130717114727.23491330@xxxxxxxxxx>
User-agent: Mutt/1.5.21 (2010-09-15)
On Wed, Jul 17, 2013 at 11:47:27AM -0400, Dwight Engen wrote:
> Use inode_capable() to check if SUID|SGID bits should be cleared to match
> similar check in inode_change_ok().
> 
> The check for CAP_LINUX_IMMUTABLE was not modified since all other file
> systems also check against init_user_ns rather than current_user_ns.
> 
> Signed-off-by: Dwight Engen <dwight.engen@xxxxxxxxxx>
> ---
>  fs/xfs/xfs_ioctl.c  | 4 ++--
>  kernel/capability.c | 1 +
>  2 files changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/xfs/xfs_ioctl.c b/fs/xfs/xfs_ioctl.c
> index 6e2bca5..8edc780 100644
> --- a/fs/xfs/xfs_ioctl.c
> +++ b/fs/xfs/xfs_ioctl.c
> @@ -981,7 +981,7 @@ xfs_ioctl_setattr(
>        * to the file owner ID, except in cases where the
>        * CAP_FSETID capability is applicable.
>        */
> -     if (current_fsuid() != ip->i_d.di_uid && !capable(CAP_FOWNER)) {
> +     if (!inode_owner_or_capable(VFS_I(ip))) {
>               code = XFS_ERROR(EPERM);
>               goto error_return;
>       }
> @@ -1103,7 +1103,7 @@ xfs_ioctl_setattr(
>                * cleared upon successful return from chown()
>                */
>               if ((ip->i_d.di_mode & (S_ISUID|S_ISGID)) &&
> -                 !capable(CAP_FSETID))
> +                 !inode_capable(VFS_I(ip), CAP_FSETID))
>                       ip->i_d.di_mode &= ~(S_ISUID|S_ISGID);
>  
>               /*
> diff --git a/kernel/capability.c b/kernel/capability.c
> index f6c2ce5..a4b6744 100644
> --- a/kernel/capability.c
> +++ b/kernel/capability.c
> @@ -464,3 +464,4 @@ bool inode_capable(const struct inode *inode, int cap)
>  
>       return ns_capable(ns, cap) && kuid_has_mapping(ns, inode->i_uid);
>  }
> +EXPORT_SYMBOL(inode_capable);

Looks good. I'm surprised that no-one else has needed this exported;
there are several non-core !capable(CAP_FSETID) checks that are
similar to this one that weren't converted to inode_capable()
checks, yet the core inode_change_ok()/setattr_copy() code was...

Regardless,

Reviewed-by: Dave Chinner <dchinner@xxxxxxxxxx>

Cheers,

Dave.
-- 
Dave Chinner
david@xxxxxxxxxxxxx

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