On Thu, Dec 06, 2018 at 08:54:03AM +0100, Greg Kurz wrote:
> Commit 66ee620f06f9 ("idr: Permit any valid kernel pointer to
> be stored") changed the radix tree lookup so that it stops when
> reaching the bottom of the tree. But radix_tree_descend() may have
> changed the node variable to point to an internal entry which then
> gets returned to the caller and bad things may happen.> pe_data is equal to R3 which is the return value of radix_tree_lookup(), > ie, 0x406 == RADIX_TREE_RETRY. Thank you for the report and the debugging! I've decided to fix the problem slightly differently, and I've also added a test to the test-suite that reproduces the problem in only a few iterations (the largest I've seen is a few hundred; and often it'll reproduce in under twenty). You can see it here: http://git.infradead.org/users/willy/linux-dax.git/commitdiff/eff3860bbfedbac6edac57fb0d7f3a60e860c1c3 I'll give the build bots a couple of days to chew on it and then ask Linus to pull it.
