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ANDROID: disable page table moves when speculative page faults are enabled

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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 <surenb@google.com>
This commit is contained in:
Suren Baghdasaryan
2022-11-18 17:06:03 -08:00
parent a1f65b39ba
commit 533a88fed7
1 changed files with 11 additions and 2 deletions
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13
mm/mremap.c
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@@ -219,7 +219,11 @@ static inline bool arch_supports_page_table_move(void)
}
#endif
#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, pmd_t *old_pmd, pmd_t *new_pmd)
{
@@ -287,7 +291,12 @@ static inline bool move_normal_pmd(struct vm_area_struct *vma,
}
#endif
#if CONFIG_PGTABLE_LEVELS > 2 && defined(CONFIG_HAVE_MOVE_PUD)
/*
* Speculative page fault handlers will not detect page table changes done
* without ptl locking.
*/
#if CONFIG_PGTABLE_LEVELS > 2 && defined(CONFIG_HAVE_MOVE_PUD) && \
!defined(CONFIG_SPECULATIVE_PAGE_FAULT)
static bool move_normal_pud(struct vm_area_struct *vma, unsigned long old_addr,
unsigned long new_addr, pud_t *old_pud, pud_t *new_pud)
{