From 7b96de5c3042f66a3064701d532ad6b9ec028496 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Maciej=20=C5=BBenczykowski?= Date: Thu, 1 Jul 2021 04:48:34 -0700 Subject: [PATCH] usb: gadget: u_ether: fix a potential null pointer dereference MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit [ Upstream commit 8ae01239609b29ec2eff55967c8e0fe3650cfa09 ] f_ncm tx timeout can call us with null skb to flush a pending frame. In this case skb is NULL to begin with but ceases to be null after dev->wrap() completes. In such a case in->maxpacket will be read, even though we've failed to check that 'in' is not NULL. Though I've never observed this fail in practice, however the 'flush operation' simply does not make sense with a null usb IN endpoint - there's nowhere to flush to... (note that we're the gadget/device, and IN is from the point of view of the host, so here IN actually means outbound...) Cc: Brooke Basile Cc: "Bryan O'Donoghue" Cc: Felipe Balbi Cc: Greg Kroah-Hartman Cc: Lorenzo Colitti Signed-off-by: Maciej Żenczykowski Link: https://lore.kernel.org/r/20210701114834.884597-6-zenczykowski@gmail.com Signed-off-by: Greg Kroah-Hartman Signed-off-by: Sasha Levin --- drivers/usb/gadget/function/u_ether.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/drivers/usb/gadget/function/u_ether.c b/drivers/usb/gadget/function/u_ether.c index 99b840daf3d9..57da62e33184 100644 --- a/drivers/usb/gadget/function/u_ether.c +++ b/drivers/usb/gadget/function/u_ether.c @@ -491,8 +491,9 @@ static netdev_tx_t eth_start_xmit(struct sk_buff *skb, } spin_unlock_irqrestore(&dev->lock, flags); - if (skb && !in) { - dev_kfree_skb_any(skb); + if (!in) { + if (skb) + dev_kfree_skb_any(skb); return NETDEV_TX_OK; }