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 <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>
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@ -487,7 +487,7 @@ static int queue_pages_pte_range(pmd_t *pmd, unsigned long addr,
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struct queue_pages *qp = walk->private;
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unsigned long flags = qp->flags;
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int nid, ret;
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pte_t *pte;
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pte_t *pte, *mapped_pte;
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spinlock_t *ptl;
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if (pmd_trans_huge(*pmd)) {
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@ -515,7 +515,7 @@ static int queue_pages_pte_range(pmd_t *pmd, unsigned long addr,
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if (pmd_trans_unstable(pmd))
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return 0;
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retry:
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pte = pte_offset_map_lock(walk->mm, pmd, addr, &ptl);
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mapped_pte = pte = pte_offset_map_lock(walk->mm, pmd, addr, &ptl);
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for (; addr != end; pte++, addr += PAGE_SIZE) {
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if (!pte_present(*pte))
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continue;
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@ -554,7 +554,7 @@ retry:
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} else
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break;
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}
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pte_unmap_unlock(pte - 1, ptl);
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pte_unmap_unlock(mapped_pte, ptl);
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cond_resched();
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return addr != end ? -EIO : 0;
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}
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