tree 73218b1077b2b1b8fed94fe8aca94326a6843b4f
parent af1ddcb5c63cfb9744c29e88db0bab6bb25ad76b
author Andrea Arcangeli <aarcange@redhat.com> 1454715373 -0800
committer Linus Torvalds <torvalds@linux-foundation.org> 1454724640 -0800

mm: validate_mm browse_rb SMP race condition

The mmap_sem for reading in validate_mm called from expand_stack is not
enough to prevent the argumented rbtree rb_subtree_gap information to
change from under us because expand_stack may be running from other
threads concurrently which will hold the mmap_sem for reading too.

The argumented rbtree is updated with vma_gap_update under the
page_table_lock so use it in browse_rb() too to avoid false positives.

Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Reported-by: Dmitry Vyukov <dvyukov@google.com>
Tested-by: Dmitry Vyukov <dvyukov@google.com>
Cc: Konstantin Khlebnikov <koct9i@gmail.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>