netdev - [PATCH] net: gtp: Fix Use-After-Free in gtp

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Message-ID: <ZiYwUnZU+50fH0SN@v4bel-B760M-AORUS-ELITE-AX>
Date: Mon, 22 Apr 2024 05:39:30 -0400
From: Hyunwoo Kim <v4bel@...ori.io>
To: pablo@...filter.or, edumazet@...gle.com, laforge@...monks.org
Cc: v4bel@...ori.io, imv4bel@...il.com, davem@...emloft.net,
	kuba@...nel.org, pabeni@...hat.com,
	osmocom-net-gprs@...ts.osmocom.org, netdev@...r.kernel.org
Subject: [PATCH] net: gtp: Fix Use-After-Free in gtp_dellink

Since call_rcu, which is called in the hlist_for_each_entry_rcu traversal
of gtp_dellink, is not part of the RCU read critical section, it
is possible that the RCU grace period will pass during the traversal and
the key will be free.

To prevent this, it should be changed to hlist_for_each_entry_safe.

Fixes: 94dc550a5062 ("gtp: fix an use-after-free in ipv4_pdp_find()")
Signed-off-by: Hyunwoo Kim <v4bel@...ori.io>
---
 drivers/net/gtp.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/net/gtp.c b/drivers/net/gtp.c
index ba4704c2c640..e62d6cbdf9bc 100644
--- a/drivers/net/gtp.c
+++ b/drivers/net/gtp.c
@@ -1098,11 +1098,12 @@ static int gtp_newlink(struct net *src_net, struct net_device *dev,
 static void gtp_dellink(struct net_device *dev, struct list_head *head)
 {
 	struct gtp_dev *gtp = netdev_priv(dev);
+	struct hlist_node *next;
 	struct pdp_ctx *pctx;
 	int i;
 
 	for (i = 0; i < gtp->hash_size; i++)
-		hlist_for_each_entry_rcu(pctx, &gtp->tid_hash[i], hlist_tid)
+		hlist_for_each_entry_safe(pctx, next, &gtp->tid_hash[i], hlist_tid)
 			pdp_context_delete(pctx);
 
 	list_del_rcu(&gtp->list);
-- 
2.34.1