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ipv6: mcast: annotate data-races around mca_flags

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/proc/net/igmp6 walks IPv6 multicast memberships under RCU and
prints mca_flags without holding idev->mc_lock. The multicast paths
update the field while holding idev->mc_lock.

Annotate this intentional lockless snapshot with READ_ONCE() and the
matching writers with WRITE_ONCE().

Signed-off-by: Yuyang Huang <sigefriedhyy@gmail.com>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Link: https://patch.msgid.link/20260609081113.7613-2-sigefriedhyy@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Yuyang Huang 2026-06-09 17:11:12 +09:00 committed by Jakub Kicinski
parent 8d8fb5b5f5
commit d0dc208808
1 changed files with 32 additions and 20 deletions
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52
net/ipv6/mcast.c
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@ -676,7 +676,7 @@ static void igmp6_group_added(struct ifmcaddr6 *mc)
return;
if (!(mc->mca_flags&MAF_LOADED)) {
mc->mca_flags |= MAF_LOADED;
WRITE_ONCE(mc->mca_flags, mc->mca_flags | MAF_LOADED);
if (ndisc_mc_map(&mc->mca_addr, buf, dev, 0) == 0)
dev_mc_add(dev, buf);
}
@ -712,7 +712,7 @@ static void igmp6_group_dropped(struct ifmcaddr6 *mc)
return;
if (mc->mca_flags&MAF_LOADED) {
mc->mca_flags &= ~MAF_LOADED;
WRITE_ONCE(mc->mca_flags, mc->mca_flags & ~MAF_LOADED);
if (ndisc_mc_map(&mc->mca_addr, buf, dev, 0) == 0)
dev_mc_del(dev, buf);
}
@ -886,7 +886,7 @@ static struct ifmcaddr6 *mca_alloc(struct inet6_dev *idev,
if (ipv6_addr_is_ll_all_nodes(&mc->mca_addr) ||
IPV6_ADDR_MC_SCOPE(&mc->mca_addr) < IPV6_ADDR_SCOPE_LINKLOCAL)
mc->mca_flags |= MAF_NOREPORT;
WRITE_ONCE(mc->mca_flags, mc->mca_flags | MAF_NOREPORT);
return mc;
}
@ -1167,7 +1167,7 @@ static void igmp6_group_queried(struct ifmcaddr6 *ma, unsigned long resptime)
if (!mod_delayed_work(mld_wq, &ma->mca_work, delay))
refcount_inc(&ma->mca_refcnt);
ma->mca_flags |= MAF_TIMER_RUNNING;
WRITE_ONCE(ma->mca_flags, ma->mca_flags | MAF_TIMER_RUNNING);
}
/* mark EXCLUDE-mode sources */
@ -1195,7 +1195,7 @@ static bool mld_xmarksources(struct ifmcaddr6 *pmc, int nsrcs,
}
}
}
pmc->mca_flags &= ~MAF_GSQUERY;
WRITE_ONCE(pmc->mca_flags, pmc->mca_flags & ~MAF_GSQUERY);
if (scount == nsrcs) /* all sources excluded */
return false;
return true;
@ -1227,10 +1227,10 @@ static bool mld_marksources(struct ifmcaddr6 *pmc, int nsrcs,
}
}
if (!scount) {
pmc->mca_flags &= ~MAF_GSQUERY;
WRITE_ONCE(pmc->mca_flags, pmc->mca_flags & ~MAF_GSQUERY);
return false;
}
pmc->mca_flags |= MAF_GSQUERY;
WRITE_ONCE(pmc->mca_flags, pmc->mca_flags | MAF_GSQUERY);
return true;
}
@ -1499,18 +1499,25 @@ static void __mld_query_work(struct sk_buff *skb)
}
} else {
for_each_mc_mclock(idev, ma) {
unsigned int flags;
if (!ipv6_addr_equal(&group, &ma->mca_addr))
continue;
if (ma->mca_flags & MAF_TIMER_RUNNING) {
flags = ma->mca_flags;
if (flags & MAF_TIMER_RUNNING) {
/* gsquery <- gsquery && mark */
if (!mark)
ma->mca_flags &= ~MAF_GSQUERY;
WRITE_ONCE(ma->mca_flags,
flags & ~MAF_GSQUERY);
} else {
/* gsquery <- mark */
if (mark)
ma->mca_flags |= MAF_GSQUERY;
WRITE_ONCE(ma->mca_flags,
flags | MAF_GSQUERY);
else
ma->mca_flags &= ~MAF_GSQUERY;
WRITE_ONCE(ma->mca_flags,
flags & ~MAF_GSQUERY);
}
if (!(ma->mca_flags & MAF_GSQUERY) ||
mld_marksources(ma, ntohs(mlh2->mld2q_nsrcs), mlh2->mld2q_srcs))
@ -1618,8 +1625,9 @@ static void __mld_report_work(struct sk_buff *skb)
if (ipv6_addr_equal(&ma->mca_addr, &mld->mld_mca)) {
if (cancel_delayed_work(&ma->mca_work))
refcount_dec(&ma->mca_refcnt);
ma->mca_flags &= ~(MAF_LAST_REPORTER |
MAF_TIMER_RUNNING);
WRITE_ONCE(ma->mca_flags,
ma->mca_flags & ~(MAF_LAST_REPORTER |
MAF_TIMER_RUNNING));
break;
}
}
@ -2018,8 +2026,10 @@ static struct sk_buff *add_grec(struct sk_buff *skb, struct ifmcaddr6 *pmc,
if (pgr)
pgr->grec_nsrcs = htons(scount);
if (isquery)
pmc->mca_flags &= ~MAF_GSQUERY; /* clear query state */
if (isquery) {
/* clear query state */
WRITE_ONCE(pmc->mca_flags, pmc->mca_flags & ~MAF_GSQUERY);
}
return skb;
}
@ -2612,7 +2622,8 @@ static void igmp6_join_group(struct ifmcaddr6 *ma)
if (!mod_delayed_work(mld_wq, &ma->mca_work, delay))
refcount_inc(&ma->mca_refcnt);
ma->mca_flags |= MAF_TIMER_RUNNING | MAF_LAST_REPORTER;
WRITE_ONCE(ma->mca_flags, ma->mca_flags |
MAF_TIMER_RUNNING | MAF_LAST_REPORTER);
}
static int ip6_mc_leave_src(struct sock *sk, struct ipv6_mc_socklist *iml,
@ -2713,8 +2724,8 @@ static void mld_mca_work(struct work_struct *work)
igmp6_send(&ma->mca_addr, ma->idev->dev, ICMPV6_MGM_REPORT);
else
mld_send_report(ma->idev, ma);
ma->mca_flags |= MAF_LAST_REPORTER;
ma->mca_flags &= ~MAF_TIMER_RUNNING;
WRITE_ONCE(ma->mca_flags, (ma->mca_flags | MAF_LAST_REPORTER) &
~MAF_TIMER_RUNNING);
mutex_unlock(&ma->idev->mc_lock);
ma_put(ma);
@ -2972,13 +2983,14 @@ 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);
seq_printf(seq,
"%-4d %-15s %pi6 %5d %08X %ld\n",
state->dev->ifindex, state->dev->name,
&im->mca_addr,
READ_ONCE(im->mca_users), im->mca_flags,
(im->mca_flags & MAF_TIMER_RUNNING) ?
READ_ONCE(im->mca_users), mca_flags,
(mca_flags & MAF_TIMER_RUNNING) ?
jiffies_to_clock_t(im->mca_work.timer.expires - jiffies) : 0);
return 0;
}