1. 16 8月, 2012 1 次提交
    • P
      netfilter: nf_ct_expect: fix possible access to uninitialized timer · 2614f864
      Pablo Neira Ayuso 提交于
      In __nf_ct_expect_check, the function refresh_timer returns 1
      if a matching expectation is found and its timer is successfully
      refreshed. This results in nf_ct_expect_related returning 0.
      Note that at this point:
      
      - the passed expectation is not inserted in the expectation table
        and its timer was not initialized, since we have refreshed one
        matching/existing expectation.
      
      - nf_ct_expect_alloc uses kmem_cache_alloc, so the expectation
        timer is in some undefined state just after the allocation,
        until it is appropriately initialized.
      
      This can be a problem for the SIP helper during the expectation
      addition:
      
       ...
       if (nf_ct_expect_related(rtp_exp) == 0) {
               if (nf_ct_expect_related(rtcp_exp) != 0)
                       nf_ct_unexpect_related(rtp_exp);
       ...
      
      Note that nf_ct_expect_related(rtp_exp) may return 0 for the timer refresh
      case that is detailed above. Then, if nf_ct_unexpect_related(rtcp_exp)
      returns != 0, nf_ct_unexpect_related(rtp_exp) is called, which does:
      
       spin_lock_bh(&nf_conntrack_lock);
       if (del_timer(&exp->timeout)) {
               nf_ct_unlink_expect(exp);
               nf_ct_expect_put(exp);
       }
       spin_unlock_bh(&nf_conntrack_lock);
      
      Note that del_timer always returns false if the timer has been
      initialized.  However, the timer was not initialized since setup_timer
      was not called, therefore, the expectation timer remains in some
      undefined state. If I'm not missing anything, this may lead to the
      removal an unexistent expectation.
      
      To fix this, the optimization that allows refreshing an expectation
      is removed. Now nf_conntrack_expect_related looks more consistent
      to me since it always add the expectation in case that it returns
      success.
      
      Thanks to Patrick McHardy for participating in the discussion of
      this patch.
      
      I think this may be the source of the problem described by:
      http://marc.info/?l=netfilter-devel&m=134073514719421&w=2Reported-by: NRafal Fitt <rafalf@aplusc.com.pl>
      Acked-by: NPatrick McHardy <kaber@trash.net>
      Signed-off-by: NPablo Neira Ayuso <pablo@netfilter.org>
      2614f864
  2. 14 8月, 2012 1 次提交
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  6. 07 8月, 2012 12 次提交