Konstantin, Andrew,
On Fri, Feb 05, 2016 at 02:19:40PM -0800, Andrew Morton wrote:
> On Fri, 5 Feb 2016 10:05:02 -0800 Jeremiah Mahler <jmmah...@gmail.com> wrote:
>
[...]
>
> This should fix it up.
>
> From: Konstantin Khlebnikov <koc...@gmail.com>
> Subject: radix-tree: fix oops after radix_tree_iter_retry
>
> Helper radix_tree_iter_retry() resets next_index to the current index. In
> following radix_tree_next_slot current chunk size becomes zero. This
> isn't checked and it tries to dereference null pointer in slot.
>
> Tagged iterator is fine because retry happens only at slot 0 where tag
> bitmask in iter->tags is filled with single bit.
>
> Fixes: 46437f9a554f ("radix-tree: fix race in gang lookup")
> Signed-off-by: Konstantin Khlebnikov <koc...@gmail.com>
> Cc: Matthew Wilcox <wi...@linux.intel.com>
> Cc: Hugh Dickins <hu...@google.com>
> Cc: Ohad Ben-Cohen <o...@wizery.com>
> Cc: Jeremiah Mahler <jmmah...@gmail.com>
> Cc: <sta...@vger.kernel.org>
> Signed-off-by: Andrew Morton <a...@linux-foundation.org>
> ---
>
> include/linux/radix-tree.h | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff -puN
> include/linux/radix-tree.h~radix-tree-fix-oops-after-radix_tree_iter_retry
> include/linux/radix-tree.h
> ---
> a/include/linux/radix-tree.h~radix-tree-fix-oops-after-radix_tree_iter_retry
> +++ a/include/linux/radix-tree.h
> @@ -400,7 +400,7 @@ void **radix_tree_iter_retry(struct radi
> * @iter: pointer to radix tree iterator
> * Returns: current chunk size
> */
> -static __always_inline unsigned
> +static __always_inline long
> radix_tree_chunk_size(struct radix_tree_iter *iter)
> {
> return iter->next_index - iter->index;
> @@ -434,9 +434,9 @@ radix_tree_next_slot(void **slot, struct
> return slot + offset + 1;
> }
> } else {
> - unsigned size = radix_tree_chunk_size(iter) - 1;
> + long size = radix_tree_chunk_size(iter);
>
> - while (size--) {
> + while (--size > 0) {
> slot++;
> iter->index++;
> if (likely(*slot))
> _
>
Fix is still working great after a couple days.
Tested-by: Jeremiah Mahler <jmmah...@gmail.com>
--
- Jeremiah Mahler
