Patch "net: gtp: Fix Use-After-Free in gtp_dellink" has been added to the 5.4-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    net: gtp: Fix Use-After-Free in gtp_dellink

to the 5.4-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     net-gtp-fix-use-after-free-in-gtp_dellink.patch
and it can be found in the queue-5.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit bccef6ef5cb8ecc7329bc928f47dd263d209a9ee
Author: Hyunwoo Kim <v4bel@xxxxxxxxx>
Date:   Mon Apr 22 05:39:30 2024 -0400

    net: gtp: Fix Use-After-Free in gtp_dellink
    
    [ Upstream commit f2a904107ee2b647bb7794a1a82b67740d7c8a64 ]
    
    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@xxxxxxxxx>
    Reviewed-by: Eric Dumazet <edumazet@xxxxxxxxxx>
    Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/drivers/net/gtp.c b/drivers/net/gtp.c
index e5961082a4afd..0d6d2fe9eabdb 100644
--- a/drivers/net/gtp.c
+++ b/drivers/net/gtp.c
@@ -706,11 +706,12 @@ 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);