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authorPeter Xu <peterx@redhat.com>2022-12-16 10:52:26 -0500
committerAndrew Morton <akpm@linux-foundation.org>2023-01-18 17:12:39 -0800
commitdd361e5033cf36c51acab996ea17748b81cedb38 (patch)
tree5b3eccbb296ae07feecfdfe622c6e051689308b3 /mm
parenteefc7fa53608920203a1402ecf7255ecfa8bb030 (diff)
mm/hugetlb: make walk_hugetlb_range() safe to pmd unshare
Since walk_hugetlb_range() walks the pgtable, it needs the vma lock to make sure the pgtable page will not be freed concurrently. Link: https://lkml.kernel.org/r/20221216155226.2043738-1-peterx@redhat.com Signed-off-by: Peter Xu <peterx@redhat.com> Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com> Reviewed-by: John Hubbard <jhubbard@nvidia.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: David Hildenbrand <david@redhat.com> Cc: James Houghton <jthoughton@google.com> Cc: Jann Horn <jannh@google.com> Cc: Miaohe Lin <linmiaohe@huawei.com> Cc: Muchun Song <songmuchun@bytedance.com> Cc: Nadav Amit <nadav.amit@gmail.com> Cc: Rik van Riel <riel@surriel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'mm')
-rw-r--r--mm/hmm.c15
-rw-r--r--mm/pagewalk.c2
2 files changed, 16 insertions, 1 deletions
diff --git a/mm/hmm.c b/mm/hmm.c
index 601a99ce3c84..6a151c09de5e 100644
--- a/mm/hmm.c
+++ b/mm/hmm.c
@@ -492,8 +492,21 @@ static int hmm_vma_walk_hugetlb_entry(pte_t *pte, unsigned long hmask,
required_fault =
hmm_pte_need_fault(hmm_vma_walk, pfn_req_flags, cpu_flags);
if (required_fault) {
+ int ret;
+
spin_unlock(ptl);
- return hmm_vma_fault(addr, end, required_fault, walk);
+ hugetlb_vma_unlock_read(vma);
+ /*
+ * Avoid deadlock: drop the vma lock before calling
+ * hmm_vma_fault(), which will itself potentially take and
+ * drop the vma lock. This is also correct from a
+ * protection point of view, because there is no further
+ * use here of either pte or ptl after dropping the vma
+ * lock.
+ */
+ ret = hmm_vma_fault(addr, end, required_fault, walk);
+ hugetlb_vma_lock_read(vma);
+ return ret;
}
pfn = pte_pfn(entry) + ((start & ~hmask) >> PAGE_SHIFT);
diff --git a/mm/pagewalk.c b/mm/pagewalk.c
index 7f1c9b274906..d98564a7be57 100644
--- a/mm/pagewalk.c
+++ b/mm/pagewalk.c
@@ -302,6 +302,7 @@ static int walk_hugetlb_range(unsigned long addr, unsigned long end,
const struct mm_walk_ops *ops = walk->ops;
int err = 0;
+ hugetlb_vma_lock_read(vma);
do {
next = hugetlb_entry_end(h, addr, end);
pte = huge_pte_offset(walk->mm, addr & hmask, sz);
@@ -314,6 +315,7 @@ static int walk_hugetlb_range(unsigned long addr, unsigned long end,
if (err)
break;
} while (addr = next, addr != end);
+ hugetlb_vma_unlock_read(vma);
return err;
}