[PATCH net-next] gtp: annotate PDP lookups under RTNL

[Runyu Xiao]

The GTP PDP lookup helpers are shared by RCU-protected data and report
paths and RTNL-protected control paths such as gtp_genl_new_pdp(). The
helpers walk RCU hlists, but they do not currently pass the RTNL
condition for the control-path lookups.

Pass lockdep_rtnl_is_held() to the PDP hlist iterators. Existing
RCU-reader callers remain valid because the RCU-list macros also accept
an active RCU read-side section; the added condition only documents the
non-RCU protection already used by RTNL control paths.

This was found by our static analysis tool and then manually reviewed
against the current tree. The dynamic triage evidence is a
target-matched CONFIG_PROVE_RCU_LIST warning; the change is limited
to documenting the existing protection contract.

This is a lockdep annotation cleanup. It does not change PDP lifetime or
hash updates.

Signed-off-by: Runyu Xiao <runyu.xiao@xxxxxxxxxx>
---
 drivers/net/gtp.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/drivers/net/gtp.c b/drivers/net/gtp.c
index 5cb59d72bc82..b94073c55f17 100644
--- a/drivers/net/gtp.c
+++ b/drivers/net/gtp.c
@@ -151,7 +151,8 @@ static struct pdp_ctx *gtp0_pdp_find(struct gtp_dev *gtp, u64 tid, u16 family)
 
 	head = &gtp->tid_hash[gtp0_hashfn(tid) % gtp->hash_size];
 
-	hlist_for_each_entry_rcu(pdp, head, hlist_tid) {
+	hlist_for_each_entry_rcu(pdp, head, hlist_tid,
+				 lockdep_rtnl_is_held()) {
 		if (pdp->af == family &&
 		    pdp->gtp_version == GTP_V0 &&
 		    pdp->u.v0.tid == tid)
@@ -168,7 +169,8 @@ static struct pdp_ctx *gtp1_pdp_find(struct gtp_dev *gtp, u32 tid, u16 family)
 
 	head = &gtp->tid_hash[gtp1u_hashfn(tid) % gtp->hash_size];
 
-	hlist_for_each_entry_rcu(pdp, head, hlist_tid) {
+	hlist_for_each_entry_rcu(pdp, head, hlist_tid,
+				 lockdep_rtnl_is_held()) {
 		if (pdp->af == family &&
 		    pdp->gtp_version == GTP_V1 &&
 		    pdp->u.v1.i_tei == tid)
@@ -185,7 +187,8 @@ static struct pdp_ctx *ipv4_pdp_find(struct gtp_dev *gtp, __be32 ms_addr)
 
 	head = &gtp->addr_hash[ipv4_hashfn(ms_addr) % gtp->hash_size];
 
-	hlist_for_each_entry_rcu(pdp, head, hlist_addr) {
+	hlist_for_each_entry_rcu(pdp, head, hlist_addr,
+				 lockdep_rtnl_is_held()) {
 		if (pdp->af == AF_INET &&
 		    pdp->ms.addr.s_addr == ms_addr)
 			return pdp;
@@ -220,7 +223,8 @@ static struct pdp_ctx *ipv6_pdp_find(struct gtp_dev *gtp,
 
 	head = &gtp->addr_hash[ipv6_hashfn(ms_addr) % gtp->hash_size];
 
-	hlist_for_each_entry_rcu(pdp, head, hlist_addr) {
+	hlist_for_each_entry_rcu(pdp, head, hlist_addr,
+				 lockdep_rtnl_is_held()) {
 		if (pdp->af == AF_INET6 &&
 		    ipv6_pdp_addr_equal(&pdp->ms.addr6, ms_addr))
 			return pdp;
-- 
2.34.1