From 8a8ae093b52ba76b650b493848d67e7b526c8751 Mon Sep 17 00:00:00 2001 From: Nadav Amit Date: Sun, 21 Nov 2021 12:40:07 -0800 Subject: hugetlbfs: flush TLBs correctly after huge_pmd_unshare commit a4a118f2eead1d6c49e00765de89878288d4b890 upstream. When __unmap_hugepage_range() calls to huge_pmd_unshare() succeed, a TLB flush is missing. This TLB flush must be performed before releasing the i_mmap_rwsem, in order to prevent an unshared PMDs page from being released and reused before the TLB flush took place. Arguably, a comprehensive solution would use mmu_gather interface to batch the TLB flushes and the PMDs page release, however it is not an easy solution: (1) try_to_unmap_one() and try_to_migrate_one() also call huge_pmd_unshare() and they cannot use the mmu_gather interface; and (2) deferring the release of the page reference for the PMDs page until after i_mmap_rwsem is dropeed can confuse huge_pmd_unshare() into thinking PMDs are shared when they are not. Fix __unmap_hugepage_range() by adding the missing TLB flush, and forcing a flush when unshare is successful. Fixes: 24669e58477e ("hugetlb: use mmu_gather instead of a temporary linked list for accumulating pages)" # 3.6 Signed-off-by: Nadav Amit Reviewed-by: Mike Kravetz Cc: Aneesh Kumar K.V Cc: KAMEZAWA Hiroyuki Cc: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- mm/hugetlb.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) (limited to 'mm/hugetlb.c') diff --git a/mm/hugetlb.c b/mm/hugetlb.c index 86a5c9852acf..4387fa138bd2 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -3290,8 +3290,11 @@ again: continue; ptl = huge_pte_lock(h, mm, ptep); - if (huge_pmd_unshare(mm, &address, ptep)) + if (huge_pmd_unshare(mm, &address, ptep)) { + tlb_flush_pmd_range(tlb, address & PUD_MASK, PUD_SIZE); + force_flush = 1; goto unlock; + } pte = huge_ptep_get(ptep); if (huge_pte_none(pte)) -- cgit v1.2.3