vxlan: vnifilter: Fix unlocked deletion of default FDB entry

JIRA: https://issues.redhat.com/browse/RHEL-115591
Upstream Status: linux.git

commit 087a9eb
Author: Ido Schimmel <[email protected]>
Date:   Wed Apr 23 17:51:31 2025 +0300

    vxlan: vnifilter: Fix unlocked deletion of default FDB entry

    When a VNI is deleted from a VXLAN device in 'vnifilter' mode, the FDB
    entry associated with the default remote (assuming one was configured)
    is deleted without holding the hash lock. This is wrong and will result
    in a warning [1] being generated by the lockdep annotation that was
    added by commit ebe6420 ("vxlan: Create wrappers for FDB lookup").

    Reproducer:

     # ip link add vx0 up type vxlan dstport 4789 external vnifilter local 192.0.2.1
     # bridge vni add vni 10010 remote 198.51.100.1 dev vx0
     # bridge vni del vni 10010 dev vx0

    Fix by acquiring the hash lock before the deletion and releasing it
    afterwards. Blame the original commit that introduced the issue rather
    than the one that exposed it.

    [1]
    WARNING: CPU: 3 PID: 392 at drivers/net/vxlan/vxlan_core.c:417 vxlan_find_mac+0x17f/0x1a0
    [...]
    RIP: 0010:vxlan_find_mac+0x17f/0x1a0
    [...]
    Call Trace:
     <TASK>
     __vxlan_fdb_delete+0xbe/0x560
     vxlan_vni_delete_group+0x2ba/0x940
     vxlan_vni_del.isra.0+0x15f/0x580
     vxlan_process_vni_filter+0x38b/0x7b0
     vxlan_vnifilter_process+0x3bb/0x510
     rtnetlink_rcv_msg+0x2f7/0xb70
     netlink_rcv_skb+0x131/0x360
     netlink_unicast+0x426/0x710
     netlink_sendmsg+0x75a/0xc20
     __sock_sendmsg+0xc1/0x150
     ____sys_sendmsg+0x5aa/0x7b0
     ___sys_sendmsg+0xfc/0x180
     __sys_sendmsg+0x121/0x1b0
     do_syscall_64+0xbb/0x1d0
     entry_SYSCALL_64_after_hwframe+0x4b/0x53

    Fixes: f9c4bb0 ("vxlan: vni filtering support on collect metadata device")
    Signed-off-by: Ido Schimmel <[email protected]>
    Reviewed-by: Nikolay Aleksandrov <[email protected]>
    Link: https://patch.msgid.link/[email protected]
    Signed-off-by: Jakub Kicinski <[email protected]>

Signed-off-by: Guillaume Nault <[email protected]>

Author: Guillaume Nault

drivers/net/vxlan/vxlan_vnifilter.c

@@ -627,14 +627,20 @@ static void vxlan_vni_delete_group(struct vxlan_dev *vxlan,
 	 * default dst remote_ip previously added for this vni
 	 */
 	if (!vxlan_addr_any(&vninode->remote_ip) ||
-	    !vxlan_addr_any(&dst->remote_ip))
+	    !vxlan_addr_any(&dst->remote_ip)) {
+		u32 hash_index = fdb_head_index(vxlan, all_zeros_mac,
+						vninode->vni);
+
+		spin_lock_bh(&vxlan->hash_lock[hash_index]);
 		__vxlan_fdb_delete(vxlan, all_zeros_mac,
 				   (vxlan_addr_any(&vninode->remote_ip) ?
 				   dst->remote_ip : vninode->remote_ip),
 				   vxlan->cfg.dst_port,
 				   vninode->vni, vninode->vni,
 				   dst->remote_ifindex,
 				   true);
+		spin_unlock_bh(&vxlan->hash_lock[hash_index]);
+	}
 
 	if (vxlan->dev->flags & IFF_UP) {
 		if (vxlan_addr_multicast(&vninode->remote_ip) &&