linux-kernel - Re: [PATCH] SUNRPC: Fix a race in xs_reset

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Message-ID: <CAHQdGtTzHbuBQTdW7vfxpOzET8hOQrXV-AE1Px7rNwu1zBMKNw@mail.gmail.com>
Date:	Thu, 17 Sep 2015 09:38:33 -0400
From:	Trond Myklebust <trond.myklebust@...marydata.com>
To:	Jeff Layton <jlayton@...chiereds.net>
Cc:	"Suzuki K. Poulose" <suzuki.poulose@....com>,
	Anna Schumaker <anna.schumaker@...app.com>,
	"J. Bruce Fields" <bfields@...ldses.org>,
	"David S. Miller" <davem@...emloft.net>,
	Linux NFS Mailing List <linux-nfs@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] SUNRPC: Fix a race in xs_reset_transport

On Tue, Sep 15, 2015 at 2:52 PM, Jeff Layton <jlayton@...chiereds.net> wrote:
> On Tue, 15 Sep 2015 16:49:23 +0100
> "Suzuki K. Poulose" <suzuki.poulose@....com> wrote:
>
>>  net/sunrpc/xprtsock.c |    9 ++++++++-
>>  1 file changed, 8 insertions(+), 1 deletion(-)
>>
>> diff --git a/net/sunrpc/xprtsock.c b/net/sunrpc/xprtsock.c
>> index 7be90bc..6f4789d 100644
>> --- a/net/sunrpc/xprtsock.c
>> +++ b/net/sunrpc/xprtsock.c
>> @@ -822,9 +822,16 @@ static void xs_reset_transport(struct sock_xprt *transport)
>>       if (atomic_read(&transport->xprt.swapper))
>>               sk_clear_memalloc(sk);
>>
>> -     kernel_sock_shutdown(sock, SHUT_RDWR);
>> +     if (sock)
>> +             kernel_sock_shutdown(sock, SHUT_RDWR);
>>
>
> Good catch, but...isn't this still racy? What prevents transport->sock
> being set to NULL after you assign it to "sock" but before calling
> kernel_sock_shutdown?

The XPRT_LOCKED state.

Cheers
   Trond
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