From 9e7f36ab5b7bf68463faa5f7b926fea8f35597bb Mon Sep 17 00:00:00 2001 From: Weiming Shi Date: Thu, 14 May 2026 05:38:08 -0700 Subject: [PATCH] net: appletalk: fix NULL pointer dereference in aarp_send_ddp() aarp_send_ddp() calls atalk_find_dev_addr(dev) in the LocalTalk fast path without checking for NULL. When the device has no AppleTalk interface configured (dev->atalk_ptr == NULL), this leads to a NULL pointer dereference at the at->s_net access. KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007] RIP: 0010:aarp_send_ddp (net/appletalk/aarp.c:552 (discriminator 2)) Call Trace: atalk_sendmsg (net/appletalk/ddp.c:1715) __sys_sendto (net/socket.c:2265 (discriminator 1)) __x64_sys_sendto (net/socket.c:2272) do_syscall_64 (arch/x86/entry/syscall_64.c:94) entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:121) Add a NULL check consistent with the other callers of atalk_find_dev_addr(). Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Reported-by: Xiang Mei Signed-off-by: Weiming Shi Link: https://patch.msgid.link/20260514123806.3085961-3-bestswngs@gmail.com Signed-off-by: Jakub Kicinski --- net/appletalk/aarp.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/net/appletalk/aarp.c b/net/appletalk/aarp.c index e7315c01a299..30493ea3c010 100644 --- a/net/appletalk/aarp.c +++ b/net/appletalk/aarp.c @@ -542,6 +542,11 @@ int aarp_send_ddp(struct net_device *dev, struct sk_buff *skb, struct ddpehdr *ddp = (struct ddpehdr *)skb->data; int ft = 2; + if (!at) { + kfree_skb(skb); + return NET_XMIT_DROP; + } + /* * Compressible ? *