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. By the way, if you'd run the radix tree test-suite, the WARN_ON_ONCE would have triggered (that's how I spotted the bug). The test-suite is getting pretty useful these days; would you mind running it in future?
