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mm: proc: Invalidate TLB after clearing soft-dirty page state 

Since commit 0758cd8304 ("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: 0758cd8304 ("asm-generic/tlb: avoid potential double flush”)
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
This commit is contained in:
Will Deacon 2021-01-27 23:53:42 +00:00 committed by Peter Zijlstra
parent 6ee1d745b7
commit 912efa17e5
1 changed files with 5 additions and 4 deletions
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9
fs/proc/task_mmu.c
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@ -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: