From: Randy MacLeod <Randy.MacLeod@xxxxxxxxxxxxx> [ Upstream commit 8bd67ebb50c0145fd2ca8681ab65eb7e8cde1afc ] Based on above commit but simplified since pskb_may_pull_reason() does not exist until 6.1. syzbot triggered an uninit value[1] error in bridge device's xmit path by sending a short (less than ETH_HLEN bytes) skb. To fix it check if we can actually pull that amount instead of assuming. Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Reported-by: syzbot+a63a1f6a062033cf0f40@xxxxxxxxxxxxxxxxxxxxxxxxx Closes: https://syzkaller.appspot.com/bug?extid=a63a1f6a062033cf0f40 Signed-off-by: Randy MacLeod <Randy.MacLeod@xxxxxxxxxxxxx> --- net/bridge/br_device.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/net/bridge/br_device.c b/net/bridge/br_device.c index d3ea9d0779fb..84e37108c6b5 100644 --- a/net/bridge/br_device.c +++ b/net/bridge/br_device.c @@ -36,6 +36,11 @@ netdev_tx_t br_dev_xmit(struct sk_buff *skb, struct net_device *dev) const unsigned char *dest; u16 vid = 0; + if (unlikely(!pskb_may_pull(skb, ETH_HLEN))) { + kfree_skb(skb); + return NETDEV_TX_OK; + } + memset(skb->cb, 0, sizeof(struct br_input_skb_cb)); rcu_read_lock(); -- 2.34.1