Currently we can end up touching PROT_MTE user pages twice on fault and once on unmap. On fault, with KASAN disabled we first clear data and then set tags to 0, and with KASAN enabled we simultaneously clear data and set tags to the KASAN random tag, and then set tags again to 0. On unmap, we poison the page by setting tags, but this is less likely to find a bug than poisoning kernel pages. This patch series fixes these inefficiencies by only touching the pages once on fault using the DC GZVA instruction to clear both data and tags, and providing the option to avoid poisoning user pages on free. Peter Collingbourne (3): kasan: use separate (un)poison implementation for integrated init arm64: mte: handle tags zeroing at page allocation time kasan: allow freed user page poisoning to be disabled with HW tags arch/arm64/include/asm/mte.h | 4 ++ arch/arm64/include/asm/page.h | 9 ++++- arch/arm64/lib/mte.S | 20 ++++++++++ arch/arm64/mm/fault.c | 25 +++++++++++++ arch/arm64/mm/proc.S | 10 +++-- include/linux/gfp.h | 18 +++++++-- include/linux/highmem.h | 8 ++++ include/linux/kasan.h | 66 ++++++++++++++++++++------------- include/linux/page-flags.h | 9 +++++ include/trace/events/mmflags.h | 9 ++++- mm/kasan/common.c | 4 +- mm/kasan/hw_tags.c | 31 ++++++++++++++++ mm/mempool.c | 6 ++- mm/page_alloc.c | 67 ++++++++++++++++++++-------------- 14 files changed, 221 insertions(+), 65 deletions(-) -- 2.31.1.607.g51e8a6a459-goog
