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author | Liam R. Howlett <Liam.Howlett@oracle.com> | 2023-03-08 17:03:10 -0500 |
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committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2023-03-30 12:49:29 +0200 |
commit | 286b0cab31bac29960e5684f6fb331d42f03b363 (patch) | |
tree | ec9f34f4fb7c10496b0bce95d44ba9b036941466 /mm | |
parent | 318b65386756de5808cc687f97da61cd16f4f8d1 (diff) | |
download | linux-286b0cab31bac29960e5684f6fb331d42f03b363.tar.gz |
mm/ksm: fix race with VMA iteration and mm_struct teardown
commit 6db504ce55bdbc575723938fc480713c9183f6a2 upstream. exit_mmap() will tear down the VMAs and maple tree with the mmap_lock held in write mode. Ensure that the maple tree is still valid by checking ksm_test_exit() after taking the mmap_lock in read mode, but before the for_each_vma() iterator dereferences a destroyed maple tree. Since the maple tree is destroyed, the flags telling lockdep to check an external lock has been cleared. Skip the for_each_vma() iterator to avoid dereferencing a maple tree without the external lock flag, which would create a lockdep warning. Link: https://lkml.kernel.org/r/20230308220310.3119196-1-Liam.Howlett@oracle.com Fixes: a5f18ba07276 ("mm/ksm: use vma iterators instead of vma linked list") Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com> Reported-by: Pengfei Xu <pengfei.xu@intel.com> Link: https://lore.kernel.org/lkml/ZAdUUhSbaa6fHS36@xpf.sh.intel.com/ Reported-by: syzbot+2ee18845e89ae76342c5@syzkaller.appspotmail.com Link: https://syzkaller.appspot.com/bug?id=64a3e95957cd3deab99df7cd7b5a9475af92c93e Acked-by: David Hildenbrand <david@redhat.com> Cc: Matthew Wilcox (Oracle) <willy@infradead.org> Cc: <heng.su@intel.com> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'mm')
-rw-r--r-- | mm/ksm.c | 11 |
1 files changed, 9 insertions, 2 deletions
diff --git a/mm/ksm.c b/mm/ksm.c index c19fcca9bc03..cb272b6fde59 100644 --- a/mm/ksm.c +++ b/mm/ksm.c @@ -960,9 +960,15 @@ static int unmerge_and_remove_all_rmap_items(void) mm = mm_slot->slot.mm; mmap_read_lock(mm); + + /* + * Exit right away if mm is exiting to avoid lockdep issue in + * the maple tree + */ + if (ksm_test_exit(mm)) + goto mm_exiting; + for_each_vma(vmi, vma) { - if (ksm_test_exit(mm)) - break; if (!(vma->vm_flags & VM_MERGEABLE) || !vma->anon_vma) continue; err = unmerge_ksm_pages(vma, @@ -971,6 +977,7 @@ static int unmerge_and_remove_all_rmap_items(void) goto error; } +mm_exiting: remove_trailing_rmap_items(&mm_slot->rmap_list); mmap_read_unlock(mm); |