On Sat, Jan 14, 2017 at 07:57:51PM -0500, Johannes Weiner wrote: > On Sat, Jan 14, 2017 at 09:31:51PM +0000, Matthew Wilcox wrote: > > From: Johannes Weiner [mailto:[email protected]] > > > On Thu, Jan 12, 2017 at 05:28:23PM -0800, Matthew Wilcox wrote: > > > > The newly introduced warning in radix_tree_free_nodes() was testing the > > > > wrong variable; it should have been 'old' instead of 'node'. Rather > > > > than replace that one instance, I noticed that we can simply put the > > > > WARN_ON_ONCE in radix_tree_node_free() and it will be just as effective. > > > > > > > > Fixes: ea07b862ac8e ("mm: workingset: fix use-after-free in shadow node > > > shrinker") > > > > Signed-off-by: Matthew Wilcox <[email protected]> > > > > > > Thanks for the fix in radix_tree_free_nodes(). But I intentionally > > > spread out the warnings to retain the line numbers. The inlining in > > > that code will obscure which tree operation ends up triggering. > > > > The backtrace should make that fairly obvious though; even if > > radix_tree_node_free() gets inlined, the caller of > > radix_tree_free_nodes() probably doesn't also call > > radix_tree_shrink() or delete_node(). You're really looking for the > > caller in the backtrace that's outside of radix-tree.c. > > Distinguishing between the radix_tree_shrink() and the delete_node() > sites was essential to find the bug whose fix added these warnings. > The former gets inlined into the latter. Not impossible to figure out > which one triggered from a full dump, but certainly less robust.
This? >From 669b5ed6e32386d634023fee29b0b8562951e734 Mon Sep 17 00:00:00 2001 From: Matthew Wilcox <[email protected]> Date: Thu, 12 Jan 2017 17:28:23 -0800 Subject: [PATCH] radix-tree: Fix private list warnings The newly introduced warning in radix_tree_free_nodes() was testing the wrong variable; it should have been 'old' instead of 'node'. Fixes: ea07b862ac8e ("mm: workingset: fix use-after-free in shadow node shrinker") Signed-off-by: Matthew Wilcox <[email protected]> Signed-off-by: Johannes Weiner <[email protected]> --- lib/radix-tree.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/lib/radix-tree.c b/lib/radix-tree.c index 0b92d605fb69..84812a9fb16f 100644 --- a/lib/radix-tree.c +++ b/lib/radix-tree.c @@ -769,7 +769,7 @@ static void radix_tree_free_nodes(struct radix_tree_node *node) struct radix_tree_node *old = child; offset = child->offset + 1; child = child->parent; - WARN_ON_ONCE(!list_empty(&node->private_list)); + WARN_ON_ONCE(!list_empty(&old->private_list)); radix_tree_node_free(old); if (old == entry_to_node(node)) return; -- 2.11.0
