Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1427803

[PATCH] mm/huge_memory: fix the memory leak due to the race

Show all headers | View raw

From: zhong jiang <zhongjiang@huawei.com>

with great pressure, I run some test cases. As a result, I found
that the THP is not freed, it is detected by check_mm().

BUG: Bad rss-counter state mm:ffff8827edb70000 idx:1 val:512

Consider the following race :

	CPU0                               CPU1
  __handle_mm_fault()
        wp_huge_pmd()
   	    do_huge_pmd_wp_page()
		pmdp_huge_clear_flush_notify()
                (pmd_none = true)
					exit_mmap()
					   unmap_vmas()
					     zap_pmd_range()
						pmd_none_or_trans_huge_or_clear_bad()
						   (result in memory leak)
                set_pmd_at()

because of CPU0 have allocated huge page before pmdp_huge_clear_notify,
and it make the pmd entry to be null. Therefore, The memory leak can occur.

The patch fix the scenario that the pmd entry can lead to be null.

Signed-off-by: zhong jiang <zhongjiang@huawei.com>
---
 mm/huge_memory.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index e10a4fe..ef04b94 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1340,11 +1340,11 @@ alloc:
 		pmd_t entry;
 		entry = mk_huge_pmd(new_page, vma->vm_page_prot);
 		entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
-		pmdp_huge_clear_flush_notify(vma, haddr, pmd);
+		pmdp_invalidate(vma, haddr, pmd);	
 		page_add_new_anon_rmap(new_page, vma, haddr, true);
 		mem_cgroup_commit_charge(new_page, memcg, false, true);
 		lru_cache_add_active_or_unevictable(new_page, vma);
-		set_pmd_at(mm, haddr, pmd, entry);
+		pmd_populate(mm, pmd, entry);
 		update_mmu_cache_pmd(vma, address, pmd);
 		if (!page) {
 			add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR);
-- 
1.8.3.1

Back to linux.kernel | Previous | Next — Next in thread | Find similar | Unroll thread

Thread

[PATCH] mm/huge_memory: fix the memory leak due to the race zhongjiang <zhongjiang@huawei.com> - 2016-06-21 16:20 +0200
  Re: [PATCH] mm/huge_memory: fix the memory leak due to the race Michal Hocko <mhocko@kernel.org> - 2016-06-21 17:00 +0200
  Re: [PATCH] mm/huge_memory: fix the memory leak due to the race "Kirill A. Shutemov" <kirill@shutemov.name> - 2016-06-21 17:40 +0200
    Re: [PATCH] mm/huge_memory: fix the memory leak due to the race "Kirill A. Shutemov" <kirill@shutemov.name> - 2016-06-21 18:40 +0200
      Re: [PATCH] mm/huge_memory: fix the memory leak due to the race zhong jiang <zhongjiang@huawei.com> - 2016-06-22 05:10 +0200
      Re: [PATCH] mm/huge_memory: fix the memory leak due to the race zhong jiang <zhongjiang@huawei.com> - 2016-06-22 12:10 +0200

csiph-web