From 78035f7a502da2bff28626bd891527aa6cbb55ce Mon Sep 17 00:00:00 2001 From: Suren Baghdasaryan Date: Fri, 18 Nov 2022 17:06:03 -0800 Subject: [PATCH] ANDROID: disable page table moves when speculative page faults are enabled move_page_tables() can move entire pmd or pud without locking individual ptes. This is problematic for speculative page faults which do not take mmap_lock because they rely on ptl lock when writing new pte value. To avoid possible race, disable move_page_tables() optimization when CONFIG_SPECULATIVE_PAGE_FAULT is enabled. Bug: 257443051 Change-Id: Ib48dda08ecad1abc60d08fc089a6566a63393c13 Signed-off-by: Suren Baghdasaryan Git-commit: 0f43357d37e4451cdc12a60895b6e4929a87adf7 Git-repo: https://android.googlesource.com/kernel/common/ [quic_c_spathi@quicinc.com: resolve trivial merge conflicts] Signed-off-by: Srinivasarao Pathipati --- mm/mremap.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/mm/mremap.c b/mm/mremap.c index f7c278e65a5d..0a026571645e 100644 --- a/mm/mremap.c +++ b/mm/mremap.c @@ -191,7 +191,11 @@ static void move_ptes(struct vm_area_struct *vma, pmd_t *old_pmd, drop_rmap_locks(vma); } -#ifdef CONFIG_HAVE_MOVE_PMD +/* + * Speculative page fault handlers will not detect page table changes done + * without ptl locking. + */ +#if defined(CONFIG_HAVE_MOVE_PMD) && !defined(CONFIG_SPECULATIVE_PAGE_FAULT) static bool move_normal_pmd(struct vm_area_struct *vma, unsigned long old_addr, unsigned long new_addr, unsigned long old_end, pmd_t *old_pmd, pmd_t *new_pmd)