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From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: "Dilger, Andreas" <andreas.dilger@intel.com>
Cc: Wenwen Wang <wang6495@umn.edu>,
	"devel@driverdev.osuosl.org" <devel@driverdev.osuosl.org>,
	Ben Evans <bevans@cray.com>, Jeff Layton <jlayton@redhat.com>,
	Aastha Gupta <aastha.gupta4104@gmail.com>,
	"kjlu@umn.edu" <kjlu@umn.edu>, NeilBrown <neilb@suse.com>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"Drokin, Oleg" <oleg.drokin@intel.com>,
	"lustre-devel@lists.lustre.org" <lustre-devel@lists.lustre.org>
Subject: Re: [PATCH] staging: luster: llite: fix a potential missing-check bug when copying lumv
Date: Sun, 29 Apr 2018 15:20:58 +0200	[thread overview]
Message-ID: <20180429132058.GB5972@kroah.com> (raw)
In-Reply-To: <8E6ADED8-592E-4794-8CAB-913A325B1971@intel.com>

On Sat, Apr 28, 2018 at 04:04:25PM +0000, Dilger, Andreas wrote:
> On Apr 27, 2018, at 17:45, Wenwen Wang <wang6495@umn.edu> wrote:
> > [PATCH] staging: luster: llite: fix potential missing-check bug when copying lumv
> 
> (typo) s/luster/lustre/
> 
> > In ll_dir_ioctl(), the object lumv3 is firstly copied from the user space
> > using Its address, i.e., lumv1 = &lumv3. If the lmm_magic field of lumv3 is
> > LOV_USER_MAGIV_V3, lumv3 will be modified by the second copy from the user
> 
> (typo) s/MAGIV/MAGIC/
> 
> > space. The second copy is necessary, because the two versions (i.e.,
> > lov_user_md_v1 and lov_user_md_v3) have different data formats and lengths.
> > However, given that the user data resides in the user space, a malicious
> > user-space process can race to change the data between the two copies. By
> > doing so, the attacker can provide a data with an inconsistent version,
> > e.g., v1 version + v3 data. This can lead to logical errors in the
> > following execution in ll_dir_setstripe(), which performs different actions
> > according to the version specified by the field lmm_magic.
> 
> This isn't a serious bug in the end.  The LOV_USER_MAGIC_V3 check just copies
> a bit more data from userspace (the lmm_pool field).  It would be more of a
> problem if the reverse was possible (copy smaller V1 buffer, but change the
> magic to LOV_USER_MAGIC_V3 afterward), but this isn't possible since the second
> copy is not done if there is a V1 magic.  If the user changes from V3 magic
> to V1 in a racy manner it means less data will be used than copied, which
> is harmless.
> 
> > This patch rechecks the version field lmm_magic in the second copy.  If the
> > version is not as expected, i.e., LOV_USER_MAGIC_V3, an error code will be
> > returned: -EINVAL.
> 
> This isn't a bad idea in any case, since it verifies the data copied from
> userspace is still valid.

So you agree with this patch?  Or do not?

confused,

greg k-h

  reply	other threads:[~2018-04-29 13:20 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-04-27 23:45 [PATCH] staging: luster: llite: fix a potential missing-check bug when copying lumv Wenwen Wang
2018-04-28 16:04 ` Dilger, Andreas
2018-04-29 13:20   ` Greg Kroah-Hartman [this message]
2018-04-29 20:58     ` Wenwen Wang
2018-04-30 11:15       ` Dan Carpenter
2018-04-30 22:38     ` Dilger, Andreas
2018-04-30 22:43       ` Wenwen Wang

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