git.ipfire.org Git - thirdparty/kernel/stable-queue.git/blob

   1 From 96e7deb0a438672dc1ad9ef1d86e43d3ebd30126 Mon Sep 17 00:00:00 2001
   2 From: Sasha Levin <sashal@kernel.org>
   3 Date: Sun, 1 Nov 2020 17:07:40 -0800
   4 Subject: mm: mempolicy: fix potential pte_unmap_unlock pte error
   5
   6 From: Shijie Luo <luoshijie1@huawei.com>
   7
   8 [ Upstream commit 3f08842098e842c51e3b97d0dcdebf810b32558e ]
   9
  10 When flags in queue_pages_pte_range don't have MPOL_MF_MOVE or
  11 MPOL_MF_MOVE_ALL bits, code breaks and passing origin pte - 1 to
  12 pte_unmap_unlock seems like not a good idea.
  13
  14 queue_pages_pte_range can run in MPOL_MF_MOVE_ALL mode which doesn't
  15 migrate misplaced pages but returns with EIO when encountering such a
  16 page.  Since commit a7f40cfe3b7a ("mm: mempolicy: make mbind() return
  17 -EIO when MPOL_MF_STRICT is specified") and early break on the first pte
  18 in the range results in pte_unmap_unlock on an underflow pte.  This can
  19 lead to lockups later on when somebody tries to lock the pte resp.
  20 page_table_lock again..
  21
  22 Fixes: a7f40cfe3b7a ("mm: mempolicy: make mbind() return -EIO when MPOL_MF_STRICT is specified")
  23 Signed-off-by: Shijie Luo <luoshijie1@huawei.com>
  24 Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
  25 Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
  26 Reviewed-by: Oscar Salvador <osalvador@suse.de>
  27 Acked-by: Michal Hocko <mhocko@suse.com>
  28 Cc: Miaohe Lin <linmiaohe@huawei.com>
  29 Cc: Feilong Lin <linfeilong@huawei.com>
  30 Cc: Shijie Luo <luoshijie1@huawei.com>
  31 Cc: <stable@vger.kernel.org>
  32 Link: https://lkml.kernel.org/r/20201019074853.50856-1-luoshijie1@huawei.com
  33 Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
  34 Signed-off-by: Sasha Levin <sashal@kernel.org>
  35 ---
  36  mm/mempolicy.c | 6 +++---
  37  1 file changed, 3 insertions(+), 3 deletions(-)
  38
  39 diff --git a/mm/mempolicy.c b/mm/mempolicy.c
  40 index a2be65bf5d8cc..2f443767fd1b4 100644
  41 --- a/mm/mempolicy.c
  42 +++ b/mm/mempolicy.c
  43 @@ -487,7 +487,7 @@ static int queue_pages_pte_range(pmd_t *pmd, unsigned long addr,
  44         struct queue_pages *qp = walk->private;
  45         unsigned long flags = qp->flags;
  46         int nid, ret;
  47 -       pte_t *pte;
  48 +       pte_t *pte, *mapped_pte;
  49         spinlock_t *ptl;
  50
  51         if (pmd_trans_huge(*pmd)) {
  52 @@ -515,7 +515,7 @@ static int queue_pages_pte_range(pmd_t *pmd, unsigned long addr,
  53         if (pmd_trans_unstable(pmd))
  54                 return 0;
  55  retry:
  56 -       pte = pte_offset_map_lock(walk->mm, pmd, addr, &ptl);
  57 +       mapped_pte = pte = pte_offset_map_lock(walk->mm, pmd, addr, &ptl);
  58         for (; addr != end; pte++, addr += PAGE_SIZE) {
  59                 if (!pte_present(*pte))
  60                         continue;
  61 @@ -554,7 +554,7 @@ retry:
  62                 } else
  63                         break;
  64         }
  65 -       pte_unmap_unlock(pte - 1, ptl);
  66 +       pte_unmap_unlock(mapped_pte, ptl);
  67         cond_resched();
  68         return addr != end ? -EIO : 0;
  69  }
  70 --
  71 2.27.0
  72