From: Will Deacon will@kernel.org
[ Upstream commit 912efa17e5121693dfbadae29768f4144a3f9e62 ]
Since commit 0758cd830494 ("asm-generic/tlb: avoid potential double flush"), TLB invalidation is elided in tlb_finish_mmu() if no entries were batched via the tlb_remove_*() functions. Consequently, the page-table modifications performed by clear_refs_write() in response to a write to /proc/<pid>/clear_refs do not perform TLB invalidation. Although this is fine when simply aging the ptes, in the case of clearing the "soft-dirty" state we can end up with entries where pte_write() is false, yet a writable mapping remains in the TLB.
Fix this by avoiding the mmu_gather API altogether: managing both the 'tlb_flush_pending' flag on the 'mm_struct' and explicit TLB invalidation for the sort-dirty path, much like mprotect() does already.
Fixes: 0758cd830494 ("asm-generic/tlb: avoid potential double flushâ) Signed-off-by: Will Deacon will@kernel.org Signed-off-by: Peter Zijlstra (Intel) peterz@infradead.org Reviewed-by: Yu Zhao yuzhao@google.com Acked-by: Peter Zijlstra (Intel) peterz@infradead.org Acked-by: Linus Torvalds torvalds@linux-foundation.org Link: https://lkml.kernel.org/r/20210127235347.1402-2-will@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- fs/proc/task_mmu.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-)
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c index 602e3a52884d8..3cec6fbef725e 100644 --- a/fs/proc/task_mmu.c +++ b/fs/proc/task_mmu.c @@ -1210,7 +1210,6 @@ static ssize_t clear_refs_write(struct file *file, const char __user *buf, struct mm_struct *mm; struct vm_area_struct *vma; enum clear_refs_types type; - struct mmu_gather tlb; int itype; int rv;
@@ -1249,7 +1248,6 @@ static ssize_t clear_refs_write(struct file *file, const char __user *buf, goto out_unlock; }
- tlb_gather_mmu(&tlb, mm, 0, -1); if (type == CLEAR_REFS_SOFT_DIRTY) { for (vma = mm->mmap; vma; vma = vma->vm_next) { if (!(vma->vm_flags & VM_SOFTDIRTY)) @@ -1258,15 +1256,18 @@ static ssize_t clear_refs_write(struct file *file, const char __user *buf, vma_set_page_prot(vma); }
+ inc_tlb_flush_pending(mm); mmu_notifier_range_init(&range, MMU_NOTIFY_SOFT_DIRTY, 0, NULL, mm, 0, -1UL); mmu_notifier_invalidate_range_start(&range); } walk_page_range(mm, 0, mm->highest_vm_end, &clear_refs_walk_ops, &cp); - if (type == CLEAR_REFS_SOFT_DIRTY) + if (type == CLEAR_REFS_SOFT_DIRTY) { mmu_notifier_invalidate_range_end(&range); - tlb_finish_mmu(&tlb, 0, -1); + flush_tlb_mm(mm); + dec_tlb_flush_pending(mm); + } out_unlock: mmap_write_unlock(mm); out_mm: