nfc/nci: Add the inconsistency check between the input data length and count

[ Upstream commit 068648a ]

write$nci(r0, &(0x7f0000000740)=ANY=[@ANYBLOB="610501"], 0xf)

Syzbot constructed a write() call with a data length of 3 bytes but a count value
of 15, which passed too little data to meet the basic requirements of the function
nci_rf_intf_activated_ntf_packet().

Therefore, increasing the comparison between data length and count value to avoid
problems caused by inconsistent data length and count.

Reported-and-tested-by: syzbot+71bfed2b2bcea46c98f2@syzkaller.appspotmail.com
Signed-off-by: Edward Adam Davis <eadavis@qq.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>

Author: ea1davis

drivers/nfc/virtual_ncidev.c

@@ -125,6 +125,10 @@ static ssize_t virtual_ncidev_write(struct file *file,
 		kfree_skb(skb);
 		return -EFAULT;
 	}
+	if (strnlen(skb->data, count) != count) {
+		kfree_skb(skb);
+		return -EINVAL;
+	}
 
 	nci_recv_frame(vdev->ndev, skb);
 	return count;