On Fri, 5 Feb 2016 10:05:02 -0800 Jeremiah Mahler <jmmah...@gmail.com> wrote:
> On a Lenovo X1 Carbon running -next (20160201+, 20160203+) I have
> experienced several system hangs. I usually notice it first when
> my browser (Chrome) stops responding but then other programs will stop
> responding as well. The only fix is a reboot. It is sporadic but it
> will usually occur once a day.
>
> In the logs there will be a
>
> unable to handle kernel NULL pointer dereference
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))
_
