On 11/12/2012 06:51 AM, Michel Lespinasse wrote: > Using the trinity fuzzer, Sasha Levin uncovered a case where > rb_subtree_gap wasn't correctly updated. > > Digging into this, the root cause was that vma insertions and removals > require both an rbtree insert or erase operation (which may trigger > tree rotations), and an update of the next vma's gap (which does not > change the tree topology, but may require iterating on the node's > ancestors to propagate the update). The rbtree rotations caused the > rb_subtree_gap values to be updated in some of the internal nodes, but > without upstream propagation. Then the subsequent update on the next > vma didn't iterate as high up the tree as it should have, as it > stopped as soon as it hit one of the internal nodes that had been > updated as part of a tree rotation. > > The fix is to impose that all rb_subtree_gap values must be up to date > before any rbtree insertion or erase, with the possible exception that > the node being erased doesn't need to have an up to date rb_subtree_gap. > > These 3 patches apply on top of the stack I previously sent (or equally, > on top of the last published mmotm). > > Michel Lespinasse (3): > mm: ensure safe rb_subtree_gap update when inserting new VMA > mm: ensure safe rb_subtree_gap update when removing VMA > mm: debug code to verify rb_subtree_gap updates are safe > > mm/mmap.c | 121 +++++++++++++++++++++++++++++++++++++------------------------ > 1 files changed, 73 insertions(+), 48 deletions(-) > Looking good: old warnings gone, no new warnings. Thanks, Sasha -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>