From: Andrew Morton <akpm@linux-foundation.org>
To: aarcange@redhat.com, akpm@linux-foundation.org,
edumazet@google.com, hughd@google.com,
kirill.shutemov@linux.intel.com, linux-mm@kvack.org,
mike.kravetz@oracle.com, mm-commits@vger.kernel.org,
shy828301@gmail.com, songliubraving@fb.com,
stable@vger.kernel.org, syzkaller@googlegroups.com,
torvalds@linux-foundation.org
Subject: [patch 03/11] khugepaged: adjust VM_BUG_ON_MM() in __khugepaged_enter()
Date: Thu, 20 Aug 2020 17:42:02 -0700 [thread overview]
Message-ID: <20200821004202.AP6gJKDLE%akpm@linux-foundation.org> (raw)
In-Reply-To: <20200820174132.67fd4a7a9359048f807a533b@linux-foundation.org>
From: Hugh Dickins <hughd@google.com>
Subject: khugepaged: adjust VM_BUG_ON_MM() in __khugepaged_enter()
syzbot crashes on the VM_BUG_ON_MM(khugepaged_test_exit(mm), mm) in
__khugepaged_enter(): yes, when one thread is about to dump core, has set
core_state, and is waiting for others, another might do something calling
__khugepaged_enter(), which now crashes because I lumped the core_state
test (known as "mmget_still_valid") into khugepaged_test_exit(). I still
think it's best to lump them together, so just in this exceptional case,
check mm->mm_users directly instead of khugepaged_test_exit().
Link: http://lkml.kernel.org/r/alpine.LSU.2.11.2008141503370.18085@eggly.anvils
Fixes: bbe98f9cadff ("khugepaged: khugepaged_test_exit() check mmget_still_valid()")
Signed-off-by: Hugh Dickins <hughd@google.com>
Reported-by: syzbot <syzkaller@googlegroups.com>
Acked-by: Yang Shi <shy828301@gmail.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Song Liu <songliubraving@fb.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: <stable@vger.kernel.org> [4.8+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---
mm/khugepaged.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/mm/khugepaged.c~khugepaged-adjust-vm_bug_on_mm-in-__khugepaged_enter
+++ a/mm/khugepaged.c
@@ -466,7 +466,7 @@ int __khugepaged_enter(struct mm_struct
return -ENOMEM;
/* __khugepaged_exit() must not run from under us */
- VM_BUG_ON_MM(khugepaged_test_exit(mm), mm);
+ VM_BUG_ON_MM(atomic_read(&mm->mm_users) == 0, mm);
if (unlikely(test_and_set_bit(MMF_VM_HUGEPAGE, &mm->flags))) {
free_mm_slot(mm_slot);
return 0;
_
next prev parent reply other threads:[~2020-08-21 0:42 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-21 0:41 incoming Andrew Morton
2020-08-21 0:41 ` [patch 01/11] mailmap: add Andi Kleen Andrew Morton
2020-08-21 0:41 ` [patch 02/11] hugetlb_cgroup: convert comma to semicolon Andrew Morton
2020-08-21 0:42 ` Andrew Morton [this message]
2020-08-21 0:42 ` [patch 04/11] mm/vunmap: add cond_resched() in vunmap_pmd_range Andrew Morton
2020-08-21 0:42 ` [patch 05/11] mm/rodata_test.c: fix missing function declaration Andrew Morton
2020-08-21 0:42 ` [patch 06/11] romfs: fix uninitialized memory leak in romfs_dev_read() Andrew Morton
2020-08-21 0:42 ` [patch 07/11] kernel/relay.c: fix memleak on destroy relay channel Andrew Morton
2020-08-21 0:42 ` [patch 08/11] uprobes: __replace_page() avoid BUG in munlock_vma_page() Andrew Morton
2020-08-21 0:42 ` [patch 09/11] squashfs: avoid bio_alloc() failure with 1Mbyte blocks Andrew Morton
2020-08-21 0:42 ` [patch 10/11] mm: include CMA pages in lowmem_reserve at boot Andrew Morton
2020-08-21 0:42 ` [patch 11/11] mm, page_alloc: fix core hung in free_pcppages_bulk() Andrew Morton
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