From: Xie He <xie.he.0...@gmail.com> Date: Wed, 5 Aug 2020 18:50:40 -0700
> 1. Added a skb->len check > > This driver expects upper layers to include a pseudo header of 1 byte > when passing down a skb for transmission. This driver will read this > 1-byte header. This patch added a skb->len check before reading the > header to make sure the header exists. > > 2. Changed to use needed_headroom instead of hard_header_len to request > necessary headroom to be allocated > > In net/packet/af_packet.c, the function packet_snd first reserves a > headroom of length (dev->hard_header_len + dev->needed_headroom). > Then if the socket is a SOCK_DGRAM socket, it calls dev_hard_header, > which calls dev->header_ops->create, to create the link layer header. > If the socket is a SOCK_RAW socket, it "un-reserves" a headroom of > length (dev->hard_header_len), and assumes the user to provide the > appropriate link layer header. > > So according to the logic of af_packet.c, dev->hard_header_len should > be the length of the header that would be created by > dev->header_ops->create. > > However, this driver doesn't provide dev->header_ops, so logically > dev->hard_header_len should be 0. > > So we should use dev->needed_headroom instead of dev->hard_header_len > to request necessary headroom to be allocated. > > This change fixes kernel panic when this driver is used with AF_PACKET > SOCK_RAW sockets. > > Call stack when panic: ... > Signed-off-by: Xie He <xie.he.0...@gmail.com> Applied and queued up for -stable, thanks.
