Pedro Falcato retported an mprotect regression [1] which was bisected back to the iterator changes for maple tree. Root cause analysis showed the mas_prev() running off the end of the VMA space (previous from 0) followed by mas_find(), would skip the first value. This patch set introduces maple state underflow/overflow so the sequence of calls on the maple state will return what the user expects. Users who encounter this bug may see mprotect(), userfaultfd_register(), and mlock() fail on VMAs mapped with address 0. [1] https://bugs.archlinux.org/task/79656 Liam R. Howlett (2): maple_tree: Add mas_is_active() to detect in-tree walks maple_tree: Add MAS_UNDERFLOW and MAS_OVERFLOW states include/linux/maple_tree.h | 11 ++ lib/maple_tree.c | 221 +++++++++++++++++++++++++++---------- lib/test_maple_tree.c | 87 ++++++++++++--- 3 files changed, 246 insertions(+), 73 deletions(-) -- 2.40.1
