From c8394812e56fbc334d815226268cea69b447d461 Mon Sep 17 00:00:00 2001 From: "Kirill A. Shutemov" Date: Fri, 24 Feb 2017 14:57:42 -0800 Subject: [PATCH] uprobes: split THPs before trying to replace them Patch series "Fix few rmap-related THP bugs", v3. The patchset fixes handing PTE-mapped THPs in page_referenced() and page_idle_clear_pte_refs(). To achieve that I've intrdocued new helper -- page_vma_mapped_walk() -- which replaces all page_check_address{,_transhuge}() and covers all THP cases. Patchset overview: - First patch fixes one uprobe bug (unrelated to the rest of the patchset, just spotted it at the same time); - Patches 2-5 fix handling PTE-mapped THPs in page_referenced(), page_idle_clear_pte_refs() and rmap core; - Patches 6-12 convert all page_check_address{,_transhuge}() users (plus remove_migration_pte()) to page_vma_mapped_walk() and drop unused helpers. I think the fixes are not critical enough for stable@ as they don't lead to crashes or hangs, only suboptimal behaviour. This patch (of 12): For THPs page_check_address() always fails. It leads to endless loop in uprobe_write_opcode(). Testcase with huge-tmpfs (uprobes cannot probe anonymous memory). mount -t debugfs none /sys/kernel/debug mount -t tmpfs -o huge=always none /mnt gcc -Wall -O2 -o /mnt/test -x c - < /sys/kernel/debug/tracing/uprobe_events echo 1 > /sys/kernel/debug/tracing/events/uprobes/enable /mnt/test Let's split THPs before trying to replace. Link: http://lkml.kernel.org/r/20170129173858.45174-2-kirill.shutemov@linux.intel.com Signed-off-by: Kirill A. Shutemov Acked-by: Rik van Riel Acked-by: Johannes Weiner Cc: Oleg Nesterov Cc: Peter Zijlstra Cc: Andrea Arcangeli Cc: Hugh Dickins Cc: Hillf Danton Cc: Srikar Dronamraju Cc: Vladimir Davydov Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- kernel/events/uprobes.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c index d416f3baf392..1e65c79e52a6 100644 --- a/kernel/events/uprobes.c +++ b/kernel/events/uprobes.c @@ -300,8 +300,8 @@ int uprobe_write_opcode(struct mm_struct *mm, unsigned long vaddr, retry: /* Read the page with vaddr into memory */ - ret = get_user_pages_remote(NULL, mm, vaddr, 1, FOLL_FORCE, &old_page, - &vma, NULL); + ret = get_user_pages_remote(NULL, mm, vaddr, 1, + FOLL_FORCE | FOLL_SPLIT, &old_page, &vma, NULL); if (ret <= 0) return ret; -- 2.34.1