re: netfilter: nf_conntrack: there maybe a bug in __nf_conntrack_confirm, when it race against get_next_corpse

On Tue, 6 Nov 2014 21:01:00 
"Jesper" [off-list ref] wrote:

There is several issues with your submission.  I'll take care of

resubmitting a patch in your name (so you will get credit in the git log).

If you care to know, issues are:
1. you are not sending to the appropriate mailing lists,  2. patch is as an

attachment (should be inlined),  3. the patch have style and white-space
issues.

Thanks, Jesper. This is my first time to submit a patch, not know much about
the rules.  I will get it soon.

quoted

if there is a race at operating ct->status, there will be in 
alternative
case:
1) IPS_DYING bit which set in get_next_corpse override other bits (e.g.
IPS_SRC_NAT_DONE_BIT), or
2) other bits (e.g. IPS_SRC_NAT_DONE_BIT) which set in 
nf_nat_setup_info override IPS_DYING bit.

Notice the set_bit() is atomic, so we don't have these issues (of bits

getting overridden).

In most cases, we do the atomic operation on ct->status (with set_bit), but
in function nf_nat_setup_info, we
assume that unconfirmed ct is always holded by current cpu, and has no race
against other cpus, so we don't
use set_bit.  
the following code is extracted from the nf_nat_setup_info:
/* Non-atomic: we own this at the moment. */
  if (maniptype == NF_NAT_MANIP_SRC)
	ct->status |= IPS_SRC_NAT;
  else
	ct->status |= IPS_DST_NAT;

--
Best regards,
  Bill Bonaparte