4.4-stable review patch. If anyone has any objections, please let me know.
------------------
From: Konstantin Khlebnikov <koct9i@xxxxxxxxx>
commit 732042821cfa106b3c20b9780e4c60fee9d68900 upstream.
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 <koct9i@xxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Ohad Ben-Cohen <ohad@xxxxxxxxxx>
Cc: Jeremiah Mahler <jmmahler@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
include/linux/radix-tree.h | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
--- a/include/linux/radix-tree.h
+++ b/include/linux/radix-tree.h
@@ -391,7 +391,7 @@ 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;
@@ -425,9 +425,9 @@ 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))
--
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