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From: Michal Schmidt <mschmidt@redhat.com>
To: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Valdis.Kletnieks@vt.edu, Tim Chen <tim.c.chen@linux.intel.com>,
	David Miller <davem@davemloft.net>,
	zheng.z.yan@intel.com, yanzheng@21cn.com, netdev@vger.kernel.org,
	sfr@canb.auug.org.au, jirislaby@gmail.com, sedat.dilek@gmail.com,
	alex.shi@intel.com
Subject: Re: [PATCH v2 net-next] af_unix: dont send SCM_CREDENTIALS by default
Date: Mon, 28 Nov 2011 14:23:05 +0100	[thread overview]
Message-ID: <4ED38B39.5010206@redhat.com> (raw)
In-Reply-To: <1316492170.2455.43.camel@edumazet-laptop>

On 09/20/2011 06:16 AM, Eric Dumazet wrote:
> Note : The man page does states :
>
> "To receive a struct ucred message the SO_PASSCRED option  must  be
> enabled  on  the socket."
>
> But it doesnt say if the SO_PASSCRED option must be enabled before the
> sender sends its message, or before receiver attempts to read it.
>
> Once a message is queued on an unix socket, flipping SO_PASSCRED cant
> change its content (adding or removing credentials), since sender might
> already have disappeared.
>
> So current code includes credentials in all sent messages, just in case
> receiver actually fetch credentials.
>
> There are probably programs that assume they can set SO_PASSCRED right
> before calling recvmsg(). Are we taking risk to break them, or are we
> gentle and provide a sysctl option to ease the transition, I dont
> know...

Such a case has just appeared:
https://bugzilla.redhat.com/show_bug.cgi?id=757628

systemd allows on-demand socket activation of services. It creates a 
listening socket without the SO_PASSCRED flag. When the first message 
arrives to the socket, systemd spawns the service and passes the 
socket's fd to it. The service sets SO_PASSCRED before actually 
receiving the message.

I can fix that in systemd, but there may be more cases like this.

Michal

  parent reply	other threads:[~2011-11-28 13:23 UTC|newest]

Thread overview: 65+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-09-04  5:44 [PATCH -next v2] unix stream: Fix use-after-free crashes Yan, Zheng
2011-09-04  7:12 ` Sedat Dilek
2011-09-04  8:23   ` Yan, Zheng
2011-09-04 15:50     ` Joe Perches
2011-09-06 16:39     ` Tim Chen
2011-09-06 16:25 ` Tim Chen
2011-09-06 17:40   ` Eric Dumazet
2011-09-06 18:50     ` Tim Chen
2011-09-06 19:01       ` Eric Dumazet
2011-09-06 19:33         ` Tim Chen
2011-09-06 19:43           ` Eric Dumazet
2011-09-06 19:59             ` Tim Chen
2011-09-06 20:19               ` Eric Dumazet
2011-09-06 22:08                 ` Tim Chen
2011-09-07  2:35                   ` Eric Dumazet
2011-09-06 23:09                 ` Yan, Zheng
2011-09-07  2:55                   ` Eric Dumazet
2011-09-16 23:35                     ` David Miller
2011-09-16 16:50                       ` Tim Chen
2011-09-19  7:57                         ` Eric Dumazet
2011-09-07  4:36                 ` Yan, Zheng 
2011-09-07  5:08                   ` Eric Dumazet
2011-09-07  5:20                     ` Yan, Zheng
     [not found]                       ` <1315381503.3400.85.camel@edumazet-laptop>
2011-09-07 12:01                         ` Tim Chen
2011-09-07 20:12                           ` Sedat Dilek
2011-09-07 20:30                             ` Sedat Dilek
2011-09-07 14:37                               ` Tim Chen
2011-09-08  0:27                                 ` Yan, Zheng
2011-09-07 21:06                                   ` Tim Chen
2011-09-07 21:15                                     ` Tim Chen
2011-09-08  6:21                                       ` Eric Dumazet
2011-09-08  4:18                                     ` Yan, Zheng
2011-09-08  5:59                                     ` Eric Dumazet
2011-09-08  6:22                                       ` Yan, Zheng
2011-09-08  7:11                                         ` Eric Dumazet
2011-09-08  7:23                                           ` Yan, Zheng
2011-09-08  7:33                                             ` Eric Dumazet
2011-09-08  9:59                                               ` Sedat Dilek
2011-09-08 13:21                                                 ` [PATCH net-next v3] af_unix: " Eric Dumazet
2011-09-08  8:37                                                   ` Tim Chen
2011-09-09  6:51                                                     ` Eric Dumazet
2011-09-09  7:58                                                       ` [PATCH net-next] af_unix: fix use after free in unix_stream_recvmsg() Eric Dumazet
2011-09-09 10:39                                                         ` Tim Chen
2011-09-09 10:41                                                       ` [PATCH net-next v3] af_unix: Fix use-after-free crashes Tim Chen
2011-09-08  7:56                                           ` [PATCH -next v2] unix stream: " Jiri Slaby
2011-09-08  8:43                                             ` Sedat Dilek
2011-09-08  7:02                                       ` Sedat Dilek
2011-09-07 21:26                           ` Eric Dumazet
2011-09-08 13:28                             ` Eric Dumazet
2011-09-08  9:24                               ` Tim Chen
2011-09-09  5:06                                 ` [PATCH net-next] af_unix: dont send SCM_CREDENTIALS by default Eric Dumazet
2011-09-12 19:15                                   ` Tim Chen
2011-09-19  1:07                                   ` David Miller
2011-09-19  4:28                                     ` Eric Dumazet
2011-09-19 15:02                                       ` Eric Dumazet
2011-09-19 15:52                                         ` [PATCH v2 " Eric Dumazet
2011-09-19 21:39                                           ` Tim Chen
2011-09-20  2:10                                             ` Valdis.Kletnieks
2011-09-20  4:16                                               ` Eric Dumazet
2011-09-22 16:15                                                 ` tim
2011-11-28 13:23                                                 ` Michal Schmidt [this message]
2011-11-28 13:38                                                   ` Eric Dumazet
2011-09-28 17:30                                           ` David Miller
2011-09-08 10:05               ` [PATCH -next v2] unix stream: Fix use-after-free crashes Sedat Dilek
2011-09-08  8:50                 ` Tim Chen

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