This is a note to let you know that I've just added the patch titled hugetlbfs: flush TLBs correctly after huge_pmd_unshare to the 4.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: hugetlbfs-flush-tlbs-correctly-after-huge_pmd_unshare.patch and it can be found in the queue-4.4 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From a4a118f2eead1d6c49e00765de89878288d4b890 Mon Sep 17 00:00:00 2001 From: Nadav Amit <namit@xxxxxxxxxx> Date: Sun, 21 Nov 2021 12:40:07 -0800 Subject: hugetlbfs: flush TLBs correctly after huge_pmd_unshare From: Nadav Amit <namit@xxxxxxxxxx> 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 <namit@xxxxxxxxxx> Reviewed-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx> Cc: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxxxxxxx> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- include/asm-generic/tlb.h | 7 +++++++ mm/hugetlb.c | 5 ++++- 2 files changed, 11 insertions(+), 1 deletion(-) --- a/include/asm-generic/tlb.h +++ b/include/asm-generic/tlb.h @@ -165,6 +165,13 @@ static inline void __tlb_reset_range(str #define tlb_end_vma __tlb_end_vma #endif +static inline void tlb_flush_pmd_range(struct mmu_gather *tlb, + unsigned long address, unsigned long size) +{ + tlb->start = min(tlb->start, address); + tlb->end = max(tlb->end, address + size); +} + #ifndef __tlb_remove_tlb_entry #define __tlb_remove_tlb_entry(tlb, ptep, address) do { } while (0) #endif --- 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)) Patches currently in stable-queue which might be from namit@xxxxxxxxxx are queue-4.4/hugetlbfs-flush-tlbs-correctly-after-huge_pmd_unshare.patch