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author | Huang Shijie <shijie.huang@arm.com> | 2016-11-08 05:44:38 (GMT) |
---|---|---|
committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2017-01-19 19:18:08 (GMT) |
commit | 2021e55d719acfebdabbb4d6d0104465f76c9158 (patch) | |
tree | d5ee9c00bba5cc2dafd9ab461bf9bd79fd01ad38 /arch/arm64 | |
parent | 736aec92c4e95a993a6e936ba3a90498975f5d62 (diff) | |
download | linux-2021e55d719acfebdabbb4d6d0104465f76c9158.tar.xz |
arm64: hugetlb: remove the wrong pmd check in find_num_contig()
commit 20156ce2365d61beaa6f5a78a7a789044e0e7acc upstream.
The find_num_contig() will return 1 when the pmd is not present.
It will cause a kernel dead loop in the following scenaro:
1.) pmd entry is not present.
2.) the page fault occurs:
... hugetlb_fault() --> hugetlb_no_page() --> set_huge_pte_at()
3.) set_huge_pte_at() will only set the first PMD entry, since the
find_num_contig just return 1 in this case. So the PMD entries
are all empty except the first one.
4.) when kernel accesses the address mapped by the second PMD entry,
a new page fault occurs:
... hugetlb_fault() --> huge_ptep_set_access_flags()
The second PMD entry is still empty now.
5.) When the kernel returns, the access will cause a page fault again.
The kernel will run like the "4)" above.
We will see a dead loop since here.
The dead loop is caught in the 32M hugetlb page (2M PMD + Contiguous bit).
This patch removes wrong pmd check, and fixes this dead loop.
This patch also removes the redundant checks for PGD/PUD in
the find_num_contig().
Acked-by: Steve Capper <steve.capper@arm.com>
Signed-off-by: Huang Shijie <shijie.huang@arm.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'arch/arm64')
-rw-r--r-- | arch/arm64/mm/hugetlbpage.c | 12 |
1 files changed, 0 insertions, 12 deletions
diff --git a/arch/arm64/mm/hugetlbpage.c b/arch/arm64/mm/hugetlbpage.c index 52f2c8f..fd96ba7 100644 --- a/arch/arm64/mm/hugetlbpage.c +++ b/arch/arm64/mm/hugetlbpage.c @@ -51,20 +51,8 @@ static int find_num_contig(struct mm_struct *mm, unsigned long addr, *pgsize = PAGE_SIZE; if (!pte_cont(pte)) return 1; - if (!pgd_present(*pgd)) { - VM_BUG_ON(!pgd_present(*pgd)); - return 1; - } pud = pud_offset(pgd, addr); - if (!pud_present(*pud)) { - VM_BUG_ON(!pud_present(*pud)); - return 1; - } pmd = pmd_offset(pud, addr); - if (!pmd_present(*pmd)) { - VM_BUG_ON(!pmd_present(*pmd)); - return 1; - } if ((pte_t *)pmd == ptep) { *pgsize = PMD_SIZE; return CONT_PMDS; |