On Tue, Jul 16 2013, Jan Kara wrote:
> With users of radix_tree_preload() run from interrupt (CFQ is one such
> possible user), the following race can happen:
>
> radix_tree_preload()
> ...
> radix_tree_insert()
> radix_tree_node_alloc()
> if (rtp->nr) {
> ret = rtp->nodes[rtp->nr - 1];
> <interrupt>
> ...
> radix_tree_preload()
> ...
> radix_tree_insert()
> radix_tree_node_alloc()
> if (rtp->nr) {
> ret = rtp->nodes[rtp->nr - 1];
>
> And we give out one radix tree node twice. That clearly results in radix
> tree corruption with different results (usually OOPS) depending on which
> two users of radix tree race.
>
> Fix the problem by disabling interrupts when working with rtp variable.
> In-interrupt user can still deplete our preloaded nodes but at least we
> won't corrupt radix trees.
Looks good to me, great catch Jan.
--
Jens Axboe
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