From: Eric Dumazet <edumazet@google.com>
To: Vasily Averin <vvs@virtuozzo.com>
Cc: netdev <netdev@vger.kernel.org>
Subject: Re: [PATCH] tcp: detect use sendpage for slab-based objects
Date: Thu, 21 Feb 2019 08:00:47 -0800 [thread overview]
Message-ID: <CANn89i+tJA1zHN9Hbw58UQOEDY2iZCAssJcZ-+Y7C=zsNW3VSA@mail.gmail.com> (raw)
In-Reply-To: <a8655149-80b9-c75d-6528-0b851ea85de8@virtuozzo.com>
On Thu, Feb 21, 2019 at 7:30 AM Vasily Averin <vvs@virtuozzo.com> wrote:
>
> There was few incidents when XFS over network block device generates
> IO requests with slab-based metadata. If these requests are processed
> via sendpage path tcp_sendpage() calls skb_can_coalesce() and merges
> neighbour slab objects into one skb fragment.
>
> If receiving side is located on the same host tcp_recvmsg() can trigger
> following BUG_ON
> usercopy: kernel memory exposure attempt detected
> from XXXXXX (kmalloc-512) (1024 bytes)
>
> This patch helps to detect the reason of similar incidents on sending side.
>
> Signed-off-by: Vasily Averin <vvs@virtuozzo.com>
> ---
> net/ipv4/tcp.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
> index 2079145a3b7c..cf9572f4fc0f 100644
> --- a/net/ipv4/tcp.c
> +++ b/net/ipv4/tcp.c
> @@ -996,6 +996,7 @@ ssize_t do_tcp_sendpages(struct sock *sk, struct page *page, int offset,
> goto wait_for_memory;
>
> if (can_coalesce) {
> + WARN_ON_ONCE(PageSlab(page));
Please use VM_WARN_ON_ONCE() to make this a nop for CONFIG_VM_DEBUG=n
Also the whole tcp_sendpage() should be protected, not only the coalescing part.
(The get_page() done few lines later should not be attempted either)
> skb_frag_size_add(&skb_shinfo(skb)->frags[i - 1], copy);
> } else {
> get_page(page);
> --
> 2.17.1
>
It seems the bug has nothing to do with TCP, and belongs to the caller.
Otherwise you need to add the check to all existing .sendpage() /
.sendpage_locked() handler out there.
next prev parent reply other threads:[~2019-02-21 16:01 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-02-21 15:30 [PATCH] tcp: detect use sendpage for slab-based objects Vasily Averin
2019-02-21 16:00 ` Eric Dumazet [this message]
2019-02-22 14:02 ` Vasily Averin
2019-02-22 16:39 ` Eric Dumazet
2019-02-25 9:15 ` Vasily Averin
2019-02-25 9:32 ` Vasily Averin
2019-03-04 12:58 ` Vasily Averin
2019-03-04 15:51 ` Eric Dumazet
2019-03-05 14:24 ` Vasily Averin
[not found] ` <CANn89iKss+mzwbeZgy3Bzct6sBe3UeyezXXGocAYtOe9pP8a9w@mail.gmail.com>
2019-03-05 15:11 ` Eric Dumazet
2019-03-05 16:44 ` Eric Dumazet
2019-03-05 18:35 ` Vasily Averin
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