From: Vasily Averin <vvs@virtuozzo.com>
To: Eric Dumazet <eric.dumazet@gmail.com>,
Christoph Paasch <christoph.paasch@gmail.com>,
"David S. Miller" <davem@davemloft.net>
Cc: Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>,
David Ahern <dsahern@kernel.org>,
Jakub Kicinski <kuba@kernel.org>, netdev <netdev@vger.kernel.org>,
linux-kernel@vger.kernel.org, kernel@openvz.org,
Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>,
Julian Wiedmann <jwi@linux.ibm.com>
Subject: Re: [PATCH net-next v4] skb_expand_head() adjust skb->truesize incorrectly
Date: Thu, 2 Sep 2021 10:33:09 +0300 [thread overview]
Message-ID: <2984f16b-7f20-e72d-1661-b942fdc4ff9b@virtuozzo.com> (raw)
In-Reply-To: <8a183782-f4b9-e12a-55d1-c4a3c4078369@virtuozzo.com>
On 9/2/21 10:13 AM, Vasily Averin wrote:
> On 9/2/21 7:48 AM, Eric Dumazet wrote:
>> On 9/1/21 9:32 PM, Eric Dumazet wrote:
>>> I think you missed netem case, in particular
>>> skb_orphan_partial() which I already pointed out.
>>>
>>> You can setup a stack of virtual devices (tunnels),
>>> with a qdisc on them, before ip6_xmit() is finally called...
>>>
>>> Socket might have been closed already.
>>>
>>> To test your patch, you could force a skb_orphan_partial() at the beginning
>>> of skb_expand_head() (extending code coverage)
>>
>> To clarify :
>>
>> It is ok to 'downgrade' an skb->destructor having a ref on sk->sk_wmem_alloc to
>> something owning a ref on sk->refcnt.
>>
>> But the opposite operation (ref on sk->sk_refcnt --> ref on sk->sk_wmem_alloc) is not safe.
>
> Could you please explain in more details, since I stil have a completely opposite point of view?
>
> Every sk referenced in skb have sk_wmem_alloc > 9
> It is assigned to 1 in sk_alloc and decremented right before last __sk_free(),
> inside both sk_free() sock_wfree() and __sock_wfree()
>
> So it is safe to adjust skb->sk->sk_wmem_alloc,
> because alive skb keeps reference to alive sk and last one keeps sk_wmem_alloc > 0
>
> So any destructor used sk->sk_refcnt will already have sk_wmem_alloc > 0,
> because last sock_put() calls sk_free().
>
> However now I'm not sure in reversed direction.
> skb_set_owner_w() check !sk_fullsock(sk) and call sock_hold(sk);
> If sk->sk_refcnt can be 0 here (i.e. after execution of old destructor inside skb_orphan)
> -- it can be trigger pointed problem:
> "refcount_add() will trigger a warning (panic under KASAN)".
>
> Could you please explain where I'm wrong?
To clarify:
I'm agree it is unsafe to call on alive skb:
skb_orphan(skb)
adjust(skb_>sk->sk_wmem_alloc)
becasue 2 reasone:
1) old destructor can decrease sk_vmem_alloc to zero and free sk
2) becasue old destructor if !sk_fullsock(sk) can call sock_out and release last sk->sk_refcnt reference.
in this case sock_hold() will trigger warning.
1) can be handled, we can adjust(sk_wmem_alloc) before skb_orphan()
but I badly understand how to handle 2nd case.
Thank you,
Vasily Averin
next prev parent reply other threads:[~2021-09-02 7:33 UTC|newest]
Thread overview: 106+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <cover.1625665132.git.vvs@virtuozzo.com>
2021-07-07 14:04 ` [PATCH IPV6 1/1] ipv6: allocate enough headroom in ip6_finish_output2() Vasily Averin
2021-07-07 14:45 ` David Ahern
2021-07-07 16:42 ` Jakub Kicinski
2021-07-07 17:41 ` Eric Dumazet
2021-07-07 17:53 ` Vasily Averin
2021-07-07 18:30 ` Jakub Kicinski
2021-07-07 18:50 ` Eric Dumazet
2021-07-09 9:04 ` [PATCH IPV6 v2 0/4] " Vasily Averin
2021-07-12 6:44 ` [PATCH IPV6 v3 0/1] " Vasily Averin
[not found] ` <cover.1626069562.git.vvs@virtuozzo.com>
2021-07-12 6:45 ` [PATCH IPV6 v3 1/1] " Vasily Averin
2021-07-12 18:30 ` patchwork-bot+netdevbpf
2021-07-13 7:46 ` Vasily Averin
2021-07-13 12:01 ` [PATCH NET v4 0/1] " Vasily Averin
[not found] ` <cover.1626177047.git.vvs@virtuozzo.com>
2021-07-13 12:01 ` [PATCH NET v4 1/1] " Vasily Averin
2021-07-18 10:44 ` Vasily Averin
2021-07-18 15:22 ` David Ahern
2021-07-18 17:04 ` David Miller
2021-07-19 7:55 ` [PATCH NET] ipv6: ip6_finish_output2: set sk into newly allocated nskb Vasily Averin
2021-07-20 10:10 ` patchwork-bot+netdevbpf
2021-07-13 12:31 ` [PATCH IPV6 v3 1/1] ipv6: allocate enough headroom in ip6_finish_output2() Vasily Averin
2021-07-12 13:26 ` [PATCH NET 0/7] skbuff: introduce pskb_realloc_headroom() Vasily Averin
[not found] ` <cover.1626093470.git.vvs@virtuozzo.com>
2021-07-12 13:26 ` [PATCH NET 1/7] " Vasily Averin
2021-07-12 17:53 ` Jakub Kicinski
2021-07-12 18:45 ` Vasily Averin
2021-07-13 20:57 ` [PATCH NET v2 0/7] skbuff: introduce skb_expand_head() Vasily Averin
2021-08-02 8:52 ` [PATCH NET v3 " Vasily Averin
[not found] ` <cover.1627891754.git.vvs@virtuozzo.com>
2021-08-02 8:52 ` [PATCH NET v3 1/7] " Vasily Averin
2021-08-02 8:52 ` [PATCH NET v3 2/7] ipv6: use skb_expand_head in ip6_finish_output2 Vasily Averin
2021-08-02 8:52 ` [PATCH NET v3 3/7] ipv6: use skb_expand_head in ip6_xmit Vasily Averin
2021-08-02 8:52 ` [PATCH NET v3 4/7] ipv4: use skb_expand_head in ip_finish_output2 Vasily Averin
2021-08-02 8:52 ` [PATCH NET v3 5/7] vrf: use skb_expand_head in vrf_finish_output Vasily Averin
2021-08-05 11:55 ` Julian Wiedmann
2021-08-05 12:55 ` Vasily Averin
2021-08-06 7:49 ` [PATCH NET v4 0/7] skbuff: introduce skb_expand_head() Vasily Averin
2021-08-06 10:14 ` David Miller
2021-08-06 12:53 ` [PATCH NET] vrf: fix null pointer dereference in vrf_finish_output() Vasily Averin
2021-08-06 22:42 ` Jakub Kicinski
2021-08-07 6:41 ` Vasily Averin
[not found] ` <cover.1628235065.git.vvs@virtuozzo.com>
2021-08-06 7:49 ` [PATCH NET v4 1/7] skbuff: introduce skb_expand_head() Vasily Averin
2021-08-06 7:50 ` [PATCH NET v4 2/7] ipv6: use skb_expand_head in ip6_finish_output2 Vasily Averin
2021-08-06 7:50 ` [PATCH NET v4 3/7] ipv6: use skb_expand_head in ip6_xmit Vasily Averin
[not found] ` <CALMXkpaay1y=0tkbnskr4gf-HTMjJJsVryh4Prnej_ws-hJvBg@mail.gmail.com>
2021-08-20 22:44 ` Christoph Paasch
2021-08-21 6:21 ` Vasily Averin
2021-08-22 17:04 ` Christoph Paasch
2021-08-22 17:13 ` Christoph Paasch
2021-08-23 5:44 ` Vasily Averin
2021-08-23 5:59 ` Vasily Averin
2021-08-23 7:56 ` [PATCH NET-NEXT] ipv6: skb_expand_head() adjust skb->truesize incorrectly Vasily Averin
2021-08-23 17:25 ` Christoph Paasch
2021-08-23 21:45 ` Eric Dumazet
2021-08-23 21:51 ` Eric Dumazet
2021-08-23 22:23 ` Eric Dumazet
2021-08-24 8:50 ` Vasily Averin
2021-08-24 17:21 ` Vasily Averin
2021-08-25 17:49 ` Christoph Paasch
2021-08-29 12:59 ` [PATCH v2] " Vasily Averin
2021-08-30 5:52 ` [PATCH net-next " Vasily Averin
2021-08-30 16:01 ` [PATCH " Eric Dumazet
2021-08-30 18:09 ` Vasily Averin
2021-08-30 18:37 ` Vasily Averin
2021-08-30 19:58 ` Eric Dumazet
2021-08-31 14:34 ` [PATCH net-next v3 RFC] " Vasily Averin
2021-08-31 19:38 ` Eric Dumazet
2021-09-01 6:20 ` Vasily Averin
2021-09-01 8:11 ` [PATCH net-next v4] " Vasily Averin
2021-09-01 16:58 ` Christoph Paasch
2021-09-01 19:17 ` Eric Dumazet
2021-09-02 3:59 ` Vasily Averin
2021-09-02 4:32 ` Eric Dumazet
2021-09-02 4:48 ` Eric Dumazet
2021-09-02 7:13 ` Vasily Averin
2021-09-02 7:33 ` Vasily Averin [this message]
2021-09-02 8:31 ` Vasily Averin
2021-09-02 11:12 ` [PATCH net-next v5] " Vasily Averin
2021-09-02 15:53 ` Christoph Paasch
2021-09-02 16:32 ` Vasily Averin
2021-09-06 18:01 ` [PATCH net v6] " Vasily Averin
2021-09-06 18:03 ` Vasily Averin
2021-08-27 15:23 ` [PATCH NET-NEXT] ipv6: " Vasily Averin
2021-08-27 16:47 ` Eric Dumazet
2021-08-28 8:01 ` Vasily Averin
2021-08-06 7:50 ` [PATCH NET v4 4/7] ipv4: use skb_expand_head in ip_finish_output2 Vasily Averin
2021-08-06 7:50 ` [PATCH NET v4 5/7] vrf: use skb_expand_head in vrf_finish_output Vasily Averin
2021-08-06 7:50 ` [PATCH NET v4 6/7] ax25: use skb_expand_head Vasily Averin
2021-08-06 7:50 ` [PATCH NET v4 7/7] bpf: use skb_expand_head in bpf_out_neigh_v4/6 Vasily Averin
2021-08-02 8:52 ` [PATCH NET v3 6/7] ax25: use skb_expand_head Vasily Averin
2021-08-02 8:52 ` [PATCH NET v3 7/7] bpf: use skb_expand_head in bpf_out_neigh_v4/6 Vasily Averin
[not found] ` <cover.1626206993.git.vvs@virtuozzo.com>
2021-07-13 20:57 ` [PATCH NET v2 1/7] skbuff: introduce skb_expand_head() Vasily Averin
2021-07-13 20:58 ` [PATCH NET v2 2/7] ipv6: use skb_expand_head in ip6_finish_output2 Vasily Averin
2021-07-13 20:58 ` [PATCH NET v2 3/7] ipv6: use skb_expand_head in ip6_xmit Vasily Averin
2021-07-13 20:58 ` [PATCH NET v2 4/7] ipv4: use skb_expand_head in ip_finish_output2 Vasily Averin
2021-07-13 20:58 ` [PATCH NET v2 5/7] vrf: use skb_expand_head in vrf_finish_output Vasily Averin
2021-07-13 20:58 ` [PATCH NET v2 6/7] ax25: use skb_expand_head Vasily Averin
2021-07-13 20:58 ` [PATCH NET v2 7/7] bpf: use skb_expand_head in bpf_out_neigh_v4/6 Vasily Averin
2021-07-12 13:26 ` [PATCH NET 2/7] ipv6: use pskb_realloc_headroom in ip6_finish_output2 Vasily Averin
2021-07-12 13:26 ` [PATCH NET 3/7] ipv6: use pskb_realloc_headroom in ip6_xmit refactoring Vasily Averin
2021-07-12 13:27 ` [PATCH NET 4/7] ipv4: use pskb_realloc_headroom in ip_finish_output2 Vasily Averin
2021-07-12 13:27 ` [PATCH NET 5/7] vrf: use pskb_realloc_headroom in vrf_finish_output Vasily Averin
2021-07-12 13:27 ` [PATCH NET 6/7] ax25: use pskb_realloc_headroom Vasily Averin
2021-07-12 13:27 ` [PATCH NET 7/7] bpf: use pskb_realloc_headroom in bpf_out_neigh_v4/6 Vasily Averin
[not found] ` <cover.1625818825.git.vvs@virtuozzo.com>
2021-07-09 9:04 ` [PATCH IPV6 v2 1/4] ipv6: allocate enough headroom in ip6_finish_output2() Vasily Averin
2021-07-09 17:58 ` David Miller
2021-07-10 2:53 ` Vasily Averin
2021-07-09 9:04 ` [PATCH IPV6 v2 2/4] ipv6: use new helper skb_expand_head() in ip6_xmit() Vasily Averin
2021-07-09 9:05 ` [PATCH IPV6 v2 3/4] ipv6: ip6_finish_output2 refactoring Vasily Averin
2021-07-09 9:05 ` [PATCH IPV6 v2 4/4] ipv6: ip6_xmit refactoring Vasily Averin
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