syzbot was able to trigger a crash [1] in page_pool_unlist()
page_pool_list() only inserts a page pool into a netdev page pool list
if a netdev was set in params.
Even if the kzalloc() call in page_pool_create happens to initialize
pool->user.list, I chose to be more explicit in page_pool_list()
adding one INIT_HLIST_NODE().
We could test in page_pool_unlist() if netdev was set,
but since netdev can be changed to lo, it seems more robust to
check if pool->user.list is hashed before calling hlist_del().
Fixes: 083772c9f972 ("net: page_pool: record pools per netdev") Reported-and-tested-by: syzbot+f9f8efb58a4db2ca98d0@syzkaller.appspotmail.com Signed-off-by: Eric Dumazet <edumazet@google.com> Tested-by: Andrew Lunn <andrew@lunn.ch> Link: https://lore.kernel.org/r/20231130092259.3797753-1-edumazet@google.com Signed-off-by: Jakub Kicinski <kuba@kernel.org>