netdev - [PATCH net-next 3/3] ipv6: mcast: annotate data-race around psf->sf_count[MCAST

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Message-ID: <20241210183352.86530-4-edumazet@google.com>
Date: Tue, 10 Dec 2024 18:33:52 +0000
From: Eric Dumazet <edumazet@...gle.com>
To: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, 
	Paolo Abeni <pabeni@...hat.com>
Cc: netdev@...r.kernel.org, Simon Horman <horms@...nel.org>, 
	David Ahern <dsahern@...nel.org>, eric.dumazet@...il.com, 
	Eric Dumazet <edumazet@...gle.com>
Subject: [PATCH net-next 3/3] ipv6: mcast: annotate data-race around psf->sf_count[MCAST_XXX]

psf->sf_count[MCAST_XXX] fields are read locklessly from
ipv6_chk_mcast_addr() and igmp6_mcf_seq_show().

Add READ_ONCE() and WRITE_ONCE() annotations accordingly.

Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
 net/ipv6/mcast.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/net/ipv6/mcast.c b/net/ipv6/mcast.c
index 09622142b0705bd81491f148dde4612c0f8fddb8..5ca8692d565d5055eeebef2a547ced217d81c7d4 100644
--- a/net/ipv6/mcast.c
+++ b/net/ipv6/mcast.c
@@ -1037,8 +1037,8 @@ bool ipv6_chk_mcast_addr(struct net_device *dev, const struct in6_addr *group,
 				break;
 		}
 		if (psf)
-			rv = psf->sf_count[MCAST_INCLUDE] ||
-				psf->sf_count[MCAST_EXCLUDE] !=
+			rv = READ_ONCE(psf->sf_count[MCAST_INCLUDE]) ||
+				READ_ONCE(psf->sf_count[MCAST_EXCLUDE]) !=
 				READ_ONCE(mc->mca_sfcount[MCAST_EXCLUDE]);
 		else
 			rv = READ_ONCE(mc->mca_sfcount[MCAST_EXCLUDE]) != 0;
@@ -2287,7 +2287,7 @@ static int ip6_mc_del1_src(struct ifmcaddr6 *pmc, int sfmode,
 		/* source filter not found, or count wrong =>  bug */
 		return -ESRCH;
 	}
-	psf->sf_count[sfmode]--;
+	WRITE_ONCE(psf->sf_count[sfmode], psf->sf_count[sfmode] - 1);
 	if (!psf->sf_count[MCAST_INCLUDE] && !psf->sf_count[MCAST_EXCLUDE]) {
 		struct inet6_dev *idev = pmc->idev;
 
@@ -2393,7 +2393,7 @@ static int ip6_mc_add1_src(struct ifmcaddr6 *pmc, int sfmode,
 			rcu_assign_pointer(pmc->mca_sources, psf);
 		}
 	}
-	psf->sf_count[sfmode]++;
+	WRITE_ONCE(psf->sf_count[sfmode], psf->sf_count[sfmode] + 1);
 	return 0;
 }
 
@@ -3079,8 +3079,8 @@ static int igmp6_mcf_seq_show(struct seq_file *seq, void *v)
 			   state->dev->ifindex, state->dev->name,
 			   &state->im->mca_addr,
 			   &psf->sf_addr,
-			   psf->sf_count[MCAST_INCLUDE],
-			   psf->sf_count[MCAST_EXCLUDE]);
+			   READ_ONCE(psf->sf_count[MCAST_INCLUDE]),
+			   READ_ONCE(psf->sf_count[MCAST_EXCLUDE]));
 	}
 	return 0;
 }
-- 
2.47.0.338.g60cca15819-goog