linux-kernel - Re: [syzbot] [bpf?] [net?] general protection fault in dev_map

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Date: Sun, 31 Mar 2024 09:31:41 +0800
From: Edward Adam Davis <eadavis@...com>
To: syzbot+af9492708df9797198d6@...kaller.appspotmail.com
Cc: linux-kernel@...r.kernel.org,
	syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [bpf?] [net?] general protection fault in dev_map_enqueue

please test null ptr deref in dev_map_enqueue

#syz test https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf.git 443574b03387

diff --git a/kernel/bpf/devmap.c b/kernel/bpf/devmap.c
index 4e2cdbb5629f..ef20de14154a 100644
--- a/kernel/bpf/devmap.c
+++ b/kernel/bpf/devmap.c
@@ -86,6 +86,7 @@ struct bpf_dtab {
 static DEFINE_PER_CPU(struct list_head, dev_flush_list);
 static DEFINE_SPINLOCK(dev_map_lock);
 static LIST_HEAD(dev_map_list);
+static bool is_valid_dst(struct bpf_dtab_netdev *obj, struct xdp_frame *xdpf);
 
 static struct hlist_head *dev_map_create_hash(unsigned int entries,
 					      int numa_node)
@@ -536,7 +537,10 @@ int dev_xdp_enqueue(struct net_device *dev, struct xdp_frame *xdpf,
 int dev_map_enqueue(struct bpf_dtab_netdev *dst, struct xdp_frame *xdpf,
 		    struct net_device *dev_rx)
 {
-	struct net_device *dev = dst->dev;
+	struct net_device *dev;
+	if (!is_valid_dst(dst, xdpf))
+		return -EINVAL;
+	dev = dst->dev;
 
 	return __xdp_enqueue(dev, xdpf, dev_rx, dst->xdp_prog);
 }