From: Prashant Bhole <bhole_prashant...@lab.ntt.co.jp> Date: Fri, 13 Jul 2018 14:40:50 +0900
> A KASAN:use-after-free bug was found related to ip6-erspan > while running selftests/net/ip6_gre_headroom.sh > > It happens because of following sequence: > - ipv6hdr pointer is obtained from skb > - skb_cow_head() is called, skb->head memory is reallocated > - old data is accessed using ipv6hdr pointer > > skb_cow_head() call was added in e41c7c68ea77 ("ip6erspan: make sure > enough headroom at xmit."), but looking at the history there was a > chance of similar bug because gre_handle_offloads() and pskb_trim() > can also reallocate skb->head memory. Fixes tag points to commit > which introduced possibility of this bug. > > This patch moves ipv6hdr pointer assignment after skb_cow_head() call. > > Fixes: 5a963eb61b7c ("ip6_gre: Add ERSPAN native tunnel support") > Signed-off-by: Prashant Bhole <bhole_prashant...@lab.ntt.co.jp> This bug goes back to 4.16, therefore applied to 'net' and queued up for -stable. Please do not submit bug fixes against 'net-next' in this situation in the future. Thanks.