linux-kernel - Re: [PATCH 2/3] mm: ensure safe rb_subtree

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <50A0FC41.5020802@redhat.com>
Date:	Mon, 12 Nov 2012 08:40:17 -0500
From:	Rik van Riel <riel@...hat.com>
To:	Michel Lespinasse <walken@...gle.com>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	Hugh Dickins <hughd@...gle.com>,
	Sasha Levin <levinsasha928@...il.com>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH 2/3] mm: ensure safe rb_subtree_gap update when removing
 VMA

On 11/12/2012 06:51 AM, Michel Lespinasse wrote:
> Using the trinity fuzzer, Sasha Levin uncovered a case where
> rb_subtree_gap wasn't correctly updated.
>
> Digging into this, the root cause was that vma insertions and removals
> require both an rbtree insert or erase operation (which may trigger
> tree rotations), and an update of the next vma's gap (which does not
> change the tree topology, but may require iterating on the node's
> ancestors to propagate the update). The rbtree rotations caused the
> rb_subtree_gap values to be updated in some of the internal nodes, but
> without upstream propagation. Then the subsequent update on the next
> vma didn't iterate as high up the tree as it should have, as it
> stopped as soon as it hit one of the internal nodes that had been
> updated as part of a tree rotation.
>
> The fix is to impose that all rb_subtree_gap values must be up to date
> before any rbtree insertion or erase, with the possible exception that
> the node being erased doesn't need to have an up to date rb_subtree_gap.
>
> This change: during VMA removal, remove VMA from the rbtree before we
> remove it from the linked list. The implication is the next vma's
> rb_subtree_gap value becomes stale when next->vm_prev is updated,
> and we want to make sure vma_rb_erase() runs before there are any
> such stale rb_subtree_gap values in the rbtree.
>
> (I don't know of a reproduceable test case for this particular issue)
>
> Signed-off-by: Michel Lespinasse <walken@...gle.com>

Reviewed-by: Rik van Riel <riel@...hat.com>


-- 
All rights reversed
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/