From: Shijie Luo luoshijie1@huawei.com
[ 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 luoshijie1@huawei.com Signed-off-by: Miaohe Lin linmiaohe@huawei.com Signed-off-by: Andrew Morton akpm@linux-foundation.org Reviewed-by: Oscar Salvador osalvador@suse.de Acked-by: Michal Hocko mhocko@suse.com Cc: Miaohe Lin linmiaohe@huawei.com Cc: Feilong Lin linfeilong@huawei.com Cc: Shijie Luo luoshijie1@huawei.com Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/20201019074853.50856-1-luoshijie1@huawei.com Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Sasha Levin sashal@kernel.org --- mm/mempolicy.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/mm/mempolicy.c b/mm/mempolicy.c index e101cac3d4a63..9ab7969ee7e30 100644 --- a/mm/mempolicy.c +++ b/mm/mempolicy.c @@ -490,14 +490,14 @@ 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; - pte_t *pte; + pte_t *pte, *mapped_pte; spinlock_t *ptl;
split_huge_page_pmd(vma, addr, pmd); if (pmd_trans_unstable(pmd)) return 0;
- 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; @@ -521,7 +521,7 @@ static int queue_pages_pte_range(pmd_t *pmd, unsigned long addr, } else break; } - pte_unmap_unlock(pte - 1, ptl); + pte_unmap_unlock(mapped_pte, ptl); cond_resched(); return addr != end ? -EIO : 0; }