netdev - Re: [PATCH net] bpf: devmap: fix use-after-free Read in __dev_map_entry

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Date:   Tue, 14 May 2019 01:33:47 +0200
From:   Daniel Borkmann <daniel@...earbox.net>
To:     Eric Dumazet <edumazet@...gle.com>,
        Alexei Starovoitov <ast@...nel.org>
Cc:     "David S . Miller" <davem@...emloft.net>,
        netdev <netdev@...r.kernel.org>,
        Eric Dumazet <eric.dumazet@...il.com>,
        bpf <bpf@...r.kernel.org>,
        syzbot+457d3e2ffbcf31aee5c0@...kaller.appspotmail.com,
        Toke Høiland-Jørgensen <toke@...hat.com>,
        Jesper Dangaard Brouer <brouer@...hat.com>
Subject: Re: [PATCH net] bpf: devmap: fix use-after-free Read in
 __dev_map_entry_free

On 05/13/2019 06:59 PM, Eric Dumazet wrote:
> synchronize_rcu() is fine when the rcu callbacks only need
> to free memory (kfree_rcu() or direct kfree() call rcu call backs)
> 
> __dev_map_entry_free() is a bit more complex, so we need to make
> sure that call queued __dev_map_entry_free() callbacks have completed.
> 
> sysbot report:
> 
> BUG: KASAN: use-after-free in dev_map_flush_old kernel/bpf/devmap.c:365
> [inline]
> BUG: KASAN: use-after-free in __dev_map_entry_free+0x2a8/0x300
> kernel/bpf/devmap.c:379
> Read of size 8 at addr ffff8801b8da38c8 by task ksoftirqd/1/18
> 
[...]
> 
> Fixes: 546ac1ffb70d ("bpf: add devmap, a map for storing net device references")
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> Reported-by: syzbot+457d3e2ffbcf31aee5c0@...kaller.appspotmail.com
> Acked-by: Toke Høiland-Jørgensen <toke@...hat.com>
> Acked-by: Jesper Dangaard Brouer <brouer@...hat.com>

Applied, thanks!