[PATCH 3.16 276/366] multicast: do not restore deleted record source filter mode to new one

[Ben Hutchings]

3.16.61-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Hangbin Liu <liuhangbin@xxxxxxxxx>

commit 08d3ffcc0cfaba36f6b86fd568cc3bc773061fa6 upstream.

There are two scenarios that we will restore deleted records. The first is
when device down and up(or unmap/remap). In this scenario the new filter
mode is same with previous one. Because we get it from in_dev->mc_list and
we do not touch it during device down and up.

The other scenario is when a new socket join a group which was just delete
and not finish sending status reports. In this scenario, we should use the
current filter mode instead of restore old one. Here are 4 cases in total.

old_socket        new_socket       before_fix       after_fix
  IN(A)             IN(A)           ALLOW(A)         ALLOW(A)
  IN(A)             EX( )           TO_IN( )         TO_EX( )
  EX( )             IN(A)           TO_EX( )         ALLOW(A)
  EX( )             EX( )           TO_EX( )         TO_EX( )

Fixes: 24803f38a5c0b (igmp: do not remove igmp souce list info when set link down)
Fixes: 1666d49e1d416 (mld: do not remove mld souce list info when set link down)
Signed-off-by: Hangbin Liu <liuhangbin@xxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 net/ipv4/igmp.c  | 3 +--
 net/ipv6/mcast.c | 3 +--
 2 files changed, 2 insertions(+), 4 deletions(-)

--- a/net/ipv4/igmp.c
+++ b/net/ipv4/igmp.c
@@ -1159,8 +1159,7 @@ static void igmpv3_del_delrec(struct in_
 	if (pmc) {
 		im->interface = pmc->interface;
 		im->crcount = in_dev->mr_qrv ?: IGMP_Unsolicited_Report_Count;
-		im->sfmode = pmc->sfmode;
-		if (pmc->sfmode == MCAST_INCLUDE) {
+		if (im->sfmode == MCAST_INCLUDE) {
 			im->tomb = pmc->tomb;
 			im->sources = pmc->sources;
 			for (psf = im->sources; psf; psf = psf->sf_next)
--- a/net/ipv6/mcast.c
+++ b/net/ipv6/mcast.c
@@ -806,8 +806,7 @@ static void mld_del_delrec(struct inet6_
 	if (pmc) {
 		im->idev = pmc->idev;
 		im->mca_crcount = idev->mc_qrv;
-		im->mca_sfmode = pmc->mca_sfmode;
-		if (pmc->mca_sfmode == MCAST_INCLUDE) {
+		if (im->mca_sfmode == MCAST_INCLUDE) {
 			im->mca_tomb = pmc->mca_tomb;
 			im->mca_sources = pmc->mca_sources;
 			for (psf = im->mca_sources; psf; psf = psf->sf_next)