Avoid the assumption that ksize(kmalloc(S)) == ksize(kmalloc(S)): when cloning an skb, save and restore truesize after pskb_expand_head(). This can occur if the allocator decides to service an allocation of the same size differently (e.g. use a different size class, or pass the allocation on to KFENCE). Because truesize is used for bookkeeping (such as sk_wmem_queued), a modified truesize of a cloned skb may result in corrupt bookkeeping and relevant warnings (such as in sk_stream_kill_queues()). Link: https://lkml.kernel.org/r/X9JR/J6dMMOy1obu@elver.google.com Reported-by: syzbot+7b99aafdcc2eedea6178@syzkaller.appspotmail.com Suggested-by: Eric Dumazet <edumazet@google.com> Signed-off-by: Marco Elver <elver@google.com> Signed-off-by: Eric Dumazet <edumazet@google.com> Link: https://lore.kernel.org/r/20210201160420.2826895-1-elver@google.com Signed-off-by: Jakub Kicinski <kuba@kernel.org>