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[ciqlts8_6] mpls: add seqcount to protect the platform_label{,s} pair #1613

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Merged
bmastbergen merged 1 commit into from
Sep 18, 2026
+34 −9
Merged

[ciqlts8_6] mpls: add seqcount to protect the platform_label{,s} pair #1613

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43 changes: 34 additions & 9 deletions net/mpls/af_mpls.c
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Original file line number Diff line number Diff line change
Expand Up @@ -36,6 +36,8 @@

#define MPLS_NEIGH_TABLE_UNSPEC (NEIGH_LINK_TABLE + 1)

static seqcount_t mpls_platform_label_seq = SEQCNT_ZERO(mpls_platform_label_seq);

static int label_limit = (1 << 20) - 1;
static int ttl_max = 255;

Expand Down Expand Up @@ -73,16 +75,32 @@ static void rtmsg_lfib(int event, u32 label, struct mpls_route *rt,
struct nlmsghdr *nlh, struct net *net, u32 portid,
unsigned int nlm_flags);

static struct mpls_route __rcu **mpls_platform_label_rcu(struct net *net,
size_t *platform_labels)
{
struct mpls_route __rcu **platform_label;
unsigned int sequence;

do {
sequence = read_seqcount_begin(&mpls_platform_label_seq);
platform_label = rcu_dereference_rtnl(net->mpls.platform_label);
*platform_labels = net->mpls.platform_labels;
} while (read_seqcount_retry(&mpls_platform_label_seq, sequence));

return platform_label;
}

static struct mpls_route *mpls_route_input_rcu(struct net *net, unsigned index)
{
struct mpls_route *rt = NULL;
struct mpls_route __rcu **platform_label;
size_t platform_labels;

if (index < net->mpls.platform_labels) {
struct mpls_route __rcu **platform_label =
rcu_dereference(net->mpls.platform_label);
rt = rcu_dereference(platform_label[index]);
}
return rt;
platform_label = mpls_platform_label_rcu(net, &platform_labels);

if (index < platform_labels)
return rcu_dereference_rtnl(platform_label[index]);

return NULL;
}

bool mpls_output_possible(const struct net_device *dev)
Expand Down Expand Up @@ -2179,8 +2197,7 @@ static int mpls_dump_routes(struct sk_buff *skb, struct netlink_callback *cb)
if (index < MPLS_LABEL_FIRST_UNRESERVED)
index = MPLS_LABEL_FIRST_UNRESERVED;

platform_label = rtnl_dereference(net->mpls.platform_label);
platform_labels = net->mpls.platform_labels;
platform_label = mpls_platform_label_rcu(net, &platform_labels);

if (filter.filter_set)
flags |= NLM_F_DUMP_FILTERED;
Expand Down Expand Up @@ -2566,8 +2583,16 @@ static int resize_platform_label_table(struct net *net, size_t limit)
}

/* Update the global pointers */
local_bh_disable();
if (IS_ENABLED(CONFIG_PREEMPT_RT))

@PlaidCat PlaidCat Sep 17, 2026

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The RT kernel is not technically supported in this code branch its an independent code branch in Rocky 8.

This is technically a NOOP but its good incase we ever need to cross promote this for anyreason to an RT kernel branch

preempt_disable();
write_seqcount_begin(&mpls_platform_label_seq);
net->mpls.platform_labels = limit;
rcu_assign_pointer(net->mpls.platform_label, labels);
write_seqcount_end(&mpls_platform_label_seq);
if (IS_ENABLED(CONFIG_PREEMPT_RT))
preempt_enable();
local_bh_enable();

rtnl_unlock();

Expand Down
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