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batman-adv: hold claim backbone gateways by reference

PATCH Applied Ao Zhou 2 participants 2 messages Apr 6 1 message not in the archive

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Ao Zhou

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#1 lore raw

PATCH 1/1 batman-adv: hold claim backbone gateways by reference

From: Haoze Xie <[email protected]>

batadv_bla_add_claim() can replace claim->backbone_gw and drop the old gateway's last reference while readers still follow the pointer.

The netlink claim dump path dereferences claim->backbone_gw->orig and takes claim->backbone_gw->crc_lock without pinning the underlying backbone gateway. batadv_bla_check_claim() still has the same naked pointer access pattern.

Reuse batadv_bla_claim_get_backbone_gw() in both readers so they operate on a stable gateway reference until the read-side work is complete. This keeps the dump and claim-check paths aligned with the lifetime rules introduced for the other BLA claim readers.

Fixes 23721387c409 ("batman-adv: add basic bridge loop avoidance code")
Fixes 04f3f5bf1883 ("batman-adv: add B.A.T.M.A.N. Dump BLA claims via netlink")
Reported-by Yifan Wu <[email protected]>
Reported-by Juefei Pu <[email protected]>
Co-developed-by Yuan Tan <[email protected]>
Signed-off-by Yuan Tan <[email protected]>
Suggested-by Xin Liu <[email protected]>
Signed-off-by Haoze Xie <[email protected]>
Signed-off-by Ao Zhou <[email protected]>
---
 net/batman-adv/bridge_loop_avoidance.c | 27 +++++++++++++++++---------
 1 file changed, 18 insertions(+), 9 deletions(-)
net/batman-adv/bridge_loop_avoidance.c +18 -9
index 49ae92b9a152..247d8502c90b 100644
@@ -2129,6 +2129,7 @@ batadv_bla_claim_dump_entry(struct sk_buff *msg, u32 portid,
 			    struct batadv_hard_iface *primary_if,
 			    struct batadv_bla_claim *claim)
 {
+	struct batadv_bla_backbone_gw *backbone_gw;
 	const u8 *primary_addr = primary_if->net_dev->dev_addr;
 	u16 backbone_crc;
 	bool is_own;

@@ -2145,32 +2146,35 @@ batadv_bla_claim_dump_entry(struct sk_buff *msg, u32 portid,
 
 	genl_dump_check_consistent(cb, hdr);
 
-	is_own = batadv_compare_eth(claim->backbone_gw->orig,
-				    primary_addr);
+	backbone_gw = batadv_bla_claim_get_backbone_gw(claim);
+
+	is_own = batadv_compare_eth(backbone_gw->orig, primary_addr);
 
-	spin_lock_bh(&claim->backbone_gw->crc_lock);
-	backbone_crc = claim->backbone_gw->crc;
-	spin_unlock_bh(&claim->backbone_gw->crc_lock);
+	spin_lock_bh(&backbone_gw->crc_lock);
+	backbone_crc = backbone_gw->crc;
+	spin_unlock_bh(&backbone_gw->crc_lock);
 
 	if (is_own)
 		if (nla_put_flag(msg, BATADV_ATTR_BLA_OWN)) {
 			genlmsg_cancel(msg, hdr);
-			goto out;
+			goto put_backbone_gw;
 		}
 
 	if (nla_put(msg, BATADV_ATTR_BLA_ADDRESS, ETH_ALEN, claim->addr) ||
 	    nla_put_u16(msg, BATADV_ATTR_BLA_VID, claim->vid) ||
 	    nla_put(msg, BATADV_ATTR_BLA_BACKBONE, ETH_ALEN,
-		    claim->backbone_gw->orig) ||
+		    backbone_gw->orig) ||
 	    nla_put_u16(msg, BATADV_ATTR_BLA_CRC,
 			backbone_crc)) {
 		genlmsg_cancel(msg, hdr);
-		goto out;
+		goto put_backbone_gw;
 	}
 
 	genlmsg_end(msg, hdr);
 	ret = 0;
 
+put_backbone_gw:
+	batadv_backbone_gw_put(backbone_gw);
 out:
 	return ret;
 }

@@ -2448,6 +2452,7 @@ int batadv_bla_backbone_dump(struct sk_buff *msg, struct netlink_callback *cb)
 bool batadv_bla_check_claim(struct batadv_priv *bat_priv,
 			    u8 *addr, unsigned short vid)
 {
+	struct batadv_bla_backbone_gw *backbone_gw;
 	struct batadv_bla_claim search_claim;
 	struct batadv_bla_claim *claim = NULL;
 	struct batadv_hard_iface *primary_if = NULL;

@@ -2470,9 +2475,13 @@ bool batadv_bla_check_claim(struct batadv_priv *bat_priv,
 	 * return false.
 	 */
 	if (claim) {
-		if (!batadv_compare_eth(claim->backbone_gw->orig,
+		backbone_gw = batadv_bla_claim_get_backbone_gw(claim);
+
+		if (!batadv_compare_eth(backbone_gw->orig,
 					primary_if->net_dev->dev_addr))
 			ret = false;
+
+		batadv_backbone_gw_put(backbone_gw);
 		batadv_claim_put(claim);
 	}
Signature · 1 line
2.53.0
maintainer Applied
#2 lore raw
Quoted 24 lines · On Monday, 6 April 2026 15:17:28 CEST Ao Zhou wrote:

From: Haoze Xie <[email protected]>

batadv_bla_add_claim() can replace claim->backbone_gw and drop the old gateway's last reference while readers still follow the pointer.

The netlink claim dump path dereferences claim->backbone_gw->orig and takes claim->backbone_gw->crc_lock without pinning the underlying backbone gateway. batadv_bla_check_claim() still has the same naked pointer access pattern.

Reuse batadv_bla_claim_get_backbone_gw() in both readers so they operate on a stable gateway reference until the read-side work is complete. This keeps the dump and claim-check paths aligned with the lifetime rules introduced for the other BLA claim readers.

Fixes 23721387c409 ("batman-adv: add basic bridge loop avoidance code")
Fixes 04f3f5bf1883 ("batman-adv: add B.A.T.M.A.N. Dump BLA claims via netlink")
Reported-by Yifan Wu <[email protected]>
Reported-by Juefei Pu <[email protected]>
Co-developed-by Yuan Tan <[email protected]>
Signed-off-by Yuan Tan <[email protected]>
Suggested-by Xin Liu <[email protected]>
Signed-off-by Haoze Xie <[email protected]>
Signed-off-by Ao Zhou <[email protected]>
Quoted 3 lines
---
 net/batman-adv/bridge_loop_avoidance.c | 27 +++++++++++++++++---------
 1 file changed, 18 insertions(+), 9 deletions(-)

Applied, thanks!

[1/1] batman-adv: hold claim backbone gateways by reference

      https://git.open-mesh.org/linux-merge.git/commit/?h=batadv/net&id=82d8701b2c930d0e96b0dbc9115a218d791cb0d2

Best regards,
---
Sven