From 5ed0bc2d3e2df994b739bc0c6f536f480ae60c13 Mon Sep 17 00:00:00 2001 From: Shijie Luo Date: Sun, 1 Nov 2020 17:07:40 -0800 Subject: [PATCH] mm: mempolicy: fix potential pte_unmap_unlock pte error [ Upstream commit 3f08842098e842c51e3b97d0dcdebf810b32558e ] When flags in queue_pages_pte_range don't have MPOL_MF_MOVE or MPOL_MF_MOVE_ALL bits, code breaks and passing origin pte - 1 to pte_unmap_unlock seems like not a good idea. queue_pages_pte_range can run in MPOL_MF_MOVE_ALL mode which doesn't migrate misplaced pages but returns with EIO when encountering such a page. Since commit a7f40cfe3b7a ("mm: mempolicy: make mbind() return -EIO when MPOL_MF_STRICT is specified") and early break on the first pte in the range results in pte_unmap_unlock on an underflow pte. This can lead to lockups later on when somebody tries to lock the pte resp. page_table_lock again.. Fixes: a7f40cfe3b7a ("mm: mempolicy: make mbind() return -EIO when MPOL_MF_STRICT is specified") Signed-off-by: Shijie Luo Signed-off-by: Miaohe Lin Signed-off-by: Andrew Morton Reviewed-by: Oscar Salvador Acked-by: Michal Hocko Cc: Miaohe Lin Cc: Feilong Lin Cc: Shijie Luo Cc: Link: https://lkml.kernel.org/r/20201019074853.50856-1-luoshijie1@huawei.com Signed-off-by: Linus Torvalds Signed-off-by: Sasha Levin --- mm/mempolicy.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/mm/mempolicy.c b/mm/mempolicy.c index a2be65bf5d8c..2f443767fd1b 100644 --- a/mm/mempolicy.c +++ b/mm/mempolicy.c @@ -487,7 +487,7 @@ static int queue_pages_pte_range(pmd_t *pmd, unsigned long addr, struct queue_pages *qp = walk->private; unsigned long flags = qp->flags; int nid, ret; - pte_t *pte; + pte_t *pte, *mapped_pte; spinlock_t *ptl; if (pmd_trans_huge(*pmd)) { @@ -515,7 +515,7 @@ static int queue_pages_pte_range(pmd_t *pmd, unsigned long addr, if (pmd_trans_unstable(pmd)) return 0; retry: - pte = pte_offset_map_lock(walk->mm, pmd, addr, &ptl); + mapped_pte = pte = pte_offset_map_lock(walk->mm, pmd, addr, &ptl); for (; addr != end; pte++, addr += PAGE_SIZE) { if (!pte_present(*pte)) continue; @@ -554,7 +554,7 @@ retry: } else break; } - pte_unmap_unlock(pte - 1, ptl); + pte_unmap_unlock(mapped_pte, ptl); cond_resched(); return addr != end ? -EIO : 0; }