linux-kernel - Re: [PATCH] infiniband: core: fix information leak to userland

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Date:	Wed, 10 Nov 2010 16:01:08 -0800
From:	Roland Dreier <rdreier@...co.com>
To:	Vasiliy Kulikov <segooon@...il.com>
Cc:	kernel-janitors@...r.kernel.org, Roland Dreier <rolandd@...co.com>,
	Sean Hefty <sean.hefty@...el.com>,
	Hal Rosenstock <hal.rosenstock@...il.com>,
	Alex Chiang <achiang@...com>, Andi Kleen <ak@...ux.intel.com>,
	Greg Kroah-Hartman <gregkh@...e.de>,
	Julia Lawall <julia@...u.dk>, linux-rdma@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] infiniband: core: fix information leak to userland

 > Structure ib_uverbs_qp_attr is copied to userland with allmost all
 > fields uninitialized (140 bytes on x86).  It leads to leaking of
 > contents of kernel stack memory.

I don't think most of the fields are uninitialized... we have:

 	memset(&qp_attr, 0, sizeof qp_attr);

and then later on,

	ib_copy_qp_attr_to_user(&resp, &qp_attr);

which actually does initialize almost all of the fields in resp.  The
things that are missing are clearing out the reserved fields in the
structures, and also resp.qp_state never gets set.

I would suggest adding code to clear the reserved fields of structures
to ib_copy_qp_attr_to_user() and ib_copy_ah_attr_to_user(), since this
will fix what looks to be the same problem in ucma_init_qp_attr() (in
drivers/infiniband/core/ucma.c).

Sean, what is intended for qp_state handling here?  It seems
ib_copy_qp_attr_to_user() should either clear it or set it to something
sensible.

 - R.
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