aoe: fix the potential use-after-free problem in aoecmd_cfg_pkts

This patch is against CVE-2023-6270. The description of cve is:

  A flaw was found in the ATA over Ethernet (AoE) driver in the Linux
  kernel. The aoecmd_cfg_pkts() function improperly updates the refcnt on
  `struct net_device`, and a use-after-free can be triggered by racing
  between the free on the struct and the access through the `skbtxq`
  global queue. This could lead to a denial of service condition or
  potential code execution.

In aoecmd_cfg_pkts(), it always calls dev_put(ifp) when skb initial
code is finished. But the net_device ifp will still be used in
later tx()->dev_queue_xmit() in kthread. Which means that the
dev_put(ifp) should NOT be called in the success path of skb
initial code in aoecmd_cfg_pkts(). Otherwise tx() may run into
use-after-free because the net_device is freed.

This patch removed the dev_put(ifp) in the success path in
aoecmd_cfg_pkts(), and added dev_put() after skb xmit in tx().

Link: https://nvd.nist.gov/vuln/detail/CVE-2023-6270
Fixes: 7562f87 ("[NET]: Rework dev_base via list_head (v3)")
Signed-off-by: Chun-Yi Lee <jlee@suse.com>
Link: https://lore.kernel.org/r/20240305082048.25526-1-jlee@suse.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Author: joeyli

drivers/block/aoe/aoecmd.c

@@ -419,13 +419,16 @@ aoecmd_cfg_pkts(ushort aoemajor, unsigned char aoeminor, struct sk_buff_head *qu
 	rcu_read_lock();
 	for_each_netdev_rcu(&init_net, ifp) {
 		dev_hold(ifp);
-		if (!is_aoe_netif(ifp))
-			goto cont;
+		if (!is_aoe_netif(ifp)) {
+			dev_put(ifp);
+			continue;
+		}
 
 		skb = new_skb(sizeof *h + sizeof *ch);
 		if (skb == NULL) {
 			printk(KERN_INFO "aoe: skb alloc failure\n");
-			goto cont;
+			dev_put(ifp);
+			continue;
 		}
 		skb_put(skb, sizeof *h + sizeof *ch);
 		skb->dev = ifp;
@@ -440,9 +443,6 @@ aoecmd_cfg_pkts(ushort aoemajor, unsigned char aoeminor, struct sk_buff_head *qu
 		h->major = cpu_to_be16(aoemajor);
 		h->minor = aoeminor;
 		h->cmd = AOECMD_CFG;
-
-cont:
-		dev_put(ifp);
 	}
 	rcu_read_unlock();
 }

drivers/block/aoe/aoenet.c

@@ -63,6 +63,7 @@ tx(int id) __must_hold(&txlock)
 			pr_warn("aoe: packet could not be sent on %s.  %s\n",
 				ifp ? ifp->name : "netif",
 				"consider increasing tx_queue_len");
+		dev_put(ifp);
 		spin_lock_irq(&txlock);
 	}
 	return 0;