[PATCH v2 net 5/5] ipv6: mcast: use jiffies_delta_to_clock_t() in igmp6_mc_seq_show()

[Eric Dumazet <edumazet@google.com>]

If a multicast group timer has expired but the delayed work has
not yet run to clear MAF_TIMER_RUNNING, expires - jiffies produces
a negative value.

Because unsigned arithmetic was used with jiffies_to_clock_t(),
expires - jiffies underflows to a huge value and reports invalid
timer durations in /proc/net/igmp6.

Use jiffies_delta_to_clock_t() with a signed long delta to properly
cap expired deltas to 0, matching IPv4 igmp_mc_seq_show() and commit
a399a8053164 ("time: jiffies_delta_to_clock_t() helper to the rescue").

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Eric Dumazet <edumazet@google.com>
---
 net/ipv6/mcast.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/ipv6/mcast.c b/net/ipv6/mcast.c
index 2290457eb8d3dd7a8d19fa9bf19f97160b7d2492..ecef55f261890c3de11c874d623d268dcb11670f 100644
--- a/net/ipv6/mcast.c
+++ b/net/ipv6/mcast.c
@@ -3029,7 +3029,7 @@ static int igmp6_mc_seq_show(struct seq_file *seq, void *v)
 	struct ifmcaddr6 *im = (struct ifmcaddr6 *)v;
 	struct igmp6_mc_iter_state *state = igmp6_mc_seq_private(seq);
 	unsigned int mca_flags = READ_ONCE(im->mca_flags);
-	unsigned long expires = READ_ONCE(im->mca_work.timer.expires);
+	long delta = READ_ONCE(im->mca_work.timer.expires) - jiffies;
 
 	seq_printf(seq,
 		   "%-4d %-15s %pi6 %5d %08X %ld\n",
@@ -3037,7 +3037,7 @@ static int igmp6_mc_seq_show(struct seq_file *seq, void *v)
 		   &im->mca_addr,
 		   READ_ONCE(im->mca_users), mca_flags,
 		   (mca_flags & MAF_TIMER_RUNNING) ?
-		   jiffies_to_clock_t(expires - jiffies) : 0);
+		   jiffies_delta_to_clock_t(delta) : 0);
 	return 0;
 }
 
-- 
2.55.0.897.gb25b4bd76c-goog