On 05/25/2018 07:37 PM, John Fastabend wrote:
> syzbot reported two related splats, a use after free and null
> pointer dereference, when a TCP socket is closed while the map is
> also being removed.
>
> The psock keeps a reference to all map slots that have a reference
> to the sock so that when the sock is closed we can clean up any
> outstanding sock{map|hash} entries. This avoids pinning a sock
> forever if the map owner fails to do proper cleanup. However, the
> result is we have two paths that can free an entry in the map. Even
> the comment in the sock{map|hash} tear down function, sock_hash_free()
> notes this:
>
> At this point no update, lookup or delete operations can happen.
> However, be aware we can still get a socket state event updates,
> and data ready callbacks that reference the psock from sk_user_data.
>
> Both removal paths omitted taking the hash bucket lock resulting
> in the case where we have two references that are in the process
> of being free'd.
>
> Reported-by: syzbot+a761b81c211794fa1...@syzkaller.appspotmail.com
> Signed-off-by: John Fastabend <john.fastab...@gmail.com>
Applied to bpf-next, thanks John!
