From: Xie He <xie.he.0...@gmail.com> Date: Fri, 24 Jul 2020 09:33:47 -0700
> This patch fixed 2 issues with the usage of skb_cow in LAPB drivers > "lapbether" and "hdlc_x25": > > 1) After skb_cow fails, kfree_skb should be called to drop a reference > to the skb. But in both drivers, kfree_skb is not called. > > 2) skb_cow should be called before skb_push so that is can ensure the > safety of skb_push. But in "lapbether", it is incorrectly called after > skb_push. > > More details about these 2 issues: > > 1) The behavior of calling kfree_skb on failure is also the behavior of > netif_rx, which is called by this function with "return netif_rx(skb);". > So this function should follow this behavior, too. > > 2) In "lapbether", skb_cow is called after skb_push. This results in 2 > logical issues: > a) skb_push is not protected by skb_cow; > b) An extra headroom of 1 byte is ensured after skb_push. This extra > headroom has no use in this function. It also has no use in the > upper-layer function that this function passes the skb to > (x25_lapb_receive_frame in net/x25/x25_dev.c). > So logically skb_cow should instead be called before skb_push. > > Cc: Eric Dumazet <eduma...@google.com> > Cc: Martin Schiller <m...@dev.tdt.de> > Signed-off-by: Xie He <xie.he.0...@gmail.com> Applied, thank you.
