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authorLiam R. Howlett <Liam.Howlett@oracle.com>2023-03-09 01:03:10 +0300
committerAndrew Morton <akpm@linux-foundation.org>2023-03-24 03:18:33 +0300
commit6db504ce55bdbc575723938fc480713c9183f6a2 (patch)
treed82307326fdc02d5923ed308d983219ff9bb759e /mm/ksm.c
parentd035230ec9937a9138921d2a0eeb99496ea7eac0 (diff)
downloadlinux-6db504ce55bdbc575723938fc480713c9183f6a2.tar.xz
mm/ksm: fix race with VMA iteration and mm_struct teardown
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>
Diffstat (limited to 'mm/ksm.c')
-rw-r--r--mm/ksm.c11
1 files changed, 9 insertions, 2 deletions
diff --git a/mm/ksm.c b/mm/ksm.c
index ad591b779d53..2b8d30068cbb 100644
--- a/mm/ksm.c
+++ b/mm/ksm.c
@@ -988,9 +988,15 @@ 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,
@@ -999,6 +1005,7 @@ 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);