On Fri, May 11, 2018 at 07:40:26AM +0200, Dmitry Vyukov wrote:
On Fri, May 11, 2018 at 1:54 AM, Paolo Bonzini pbonzini@redhat.com wrote:
On 10/05/2018 21:16, Roman Kagan wrote:
If an IDR contains a single entry at index==0, the underlying radix tree has a single item in its root node, in which case __radix_tree_lookup(index!=0) doesn't set its *@nodep argument (in addition to returning NULL).
However, the tree itself is not empty, i.e. the tree root doesn't have IDR_FREE tag.
As a result, on an attempt to remove an index!=0 entry from such an IDR, radix_tree_delete_item doesn't return early and calls __radix_tree_delete with invalid parameters which are then dereferenced.
Reported-by: syzbot+35666cba7f0a337e2e79@syzkaller.appspotmail.com Signed-off-by: Roman Kagan rkagan@virtuozzo.com
lib/radix-tree.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/lib/radix-tree.c b/lib/radix-tree.c index da9e10c827df..10ff1bfae952 100644 --- a/lib/radix-tree.c +++ b/lib/radix-tree.c @@ -2040,8 +2040,9 @@ void *radix_tree_delete_item(struct radix_tree_root *root, void *entry;
entry = __radix_tree_lookup(root, index, &node, &slot);
if (!entry && (!is_idr(root) || node_tag_get(root, node, IDR_FREE,get_slot_offset(node, slot))))
if (!entry && (!is_idr(root) || !node ||node_tag_get(root, node, IDR_FREE,get_slot_offset(node, slot)))) return NULL; if (item && entry != item)I cannot really vouch for the patch, but if it is correct it's definitely stuff for stable. The KVM testcase is only for 4.17-rc but this is a really nasty bug in a core data structure.
Cc: stable@vger.kernel.org
Should radix-tree be compilable in userspace, so that we can add unit tests for it?...
Good point.
For my education, what/where are the tests that run as user-space code?
Actually there are userspace tests for it under tools/tests/radix-tree, but I didn't manage to get them to build. Looks like the recent introduction of a spin_lock in the radix_tree structure (for XArray work?) broke them.
Roman.