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From: David Laight <David.Laight@ACULAB.COM>
To: 'Christoph Hellwig' <hch@lst.de>, David Howells <dhowells@redhat.com>
Cc: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>,
	"linux-nvme@lists.infradead.org" <linux-nvme@lists.infradead.org>,
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	Eric Dumazet <edumazet@google.com>, Jon Maloy <jmaloy@redhat.com>,
	Ying Xue <ying.xue@windriver.com>,
	"David S. Miller" <davem@davemloft.net>,
	"ocfs2-devel@oss.oracle.com" <ocfs2-devel@oss.oracle.com>
Subject: RE: [PATCH 27/33] sctp: export sctp_setsockopt_bindx
Date: Sat, 16 May 2020 15:21:15 +0000
Message-ID: <c23030de384747ae83c6c0813bd4f1c0@AcuMS.aculab.com> (raw)
In-Reply-To: <20200515152459.GA28995@lst.de>

From: Christoph Hellwig
> Sent: 15 May 2020 16:25
> On Fri, May 15, 2020 at 04:20:02PM +0100, David Howells wrote:
> > Christoph Hellwig <hch@lst.de> wrote:
> >
> > > > The advantage on using kernel_setsockopt here is that sctp module will
> > > > only be loaded if dlm actually creates a SCTP socket.  With this
> > > > change, sctp will be loaded on setups that may not be actually using
> > > > it. It's a quite big module and might expose the system.
> > >
> > > True.  Not that the intent is to kill kernel space callers of setsockopt,
> > > as I plan to remove the set_fs address space override used for it.
> >
> > For getsockopt, does it make sense to have the core kernel load optval/optlen
> > into a buffer before calling the protocol driver?  Then the driver need not
> > see the userspace pointer at all.
> >
> > Similar could be done for setsockopt - allocate a buffer of the size requested
> > by the user inside the kernel and pass it into the driver, then copy the data
> > back afterwards.
> 
> I did look into that initially.  The problem is that tons of sockopts
> entirely ignore optlen and just use a fixed size.  So I fear that there
> could be tons of breakage if we suddently respect it.  Otherwise that
> would be a pretty nice way to handle the situation.

I'd guess that most application use the correct size for setsockopt().
(Well, apart from using 4 instead of 1.)

It is certainly possible to always try to read in 64 bytes
regardless of the supplied length, but handle the EFAULT case
by shortening the buffer.

Historically getsockopt() only wrote the length back.
Treating 0 and garbage as (say) 4k and letting the protocol
code set a shorten the copy to user might work.
All short transfers would want to use an on-stack buffer,
so slight oversizes could also be allowed for.

OTOH if i did a getsockopt() with too short a length I wouldn't
want the kernel to trash my program memory.

	David

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Thread overview: 76+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-13  6:26 remove kernel_setsockopt and kernel_getsockopt Christoph Hellwig
2020-05-13  6:26 ` [PATCH 01/33] net: add sock_set_reuseaddr Christoph Hellwig
2020-05-13  6:26 ` [PATCH 02/33] net: add sock_set_linger Christoph Hellwig
2020-05-13  6:26 ` [PATCH 03/33] net: add sock_set_priority Christoph Hellwig
2020-05-13  6:26 ` [PATCH 04/33] net: add sock_set_sndtimeo Christoph Hellwig
2020-05-13  6:26 ` [PATCH 05/33] net: add sock_bindtoindex Christoph Hellwig
2020-05-13  6:26 ` [PATCH 06/33] net: add sock_set_timestamps Christoph Hellwig
2020-05-13  6:26 ` [PATCH 07/33] net: add sock_set_keepalive Christoph Hellwig
2020-05-13  6:26 ` [PATCH 08/33] net: add sock_set_rcvbuf Christoph Hellwig
2020-05-13  6:26 ` [PATCH 09/33] net: add sock_set_reuseport Christoph Hellwig
2020-05-13  6:26 ` [PATCH 10/33] tcp: add tcp_sock_set_cork Christoph Hellwig
2020-05-13  6:26 ` [PATCH 11/33] tcp: tcp_sock_set_nodelay Christoph Hellwig
2020-05-13 12:51   ` Jason Gunthorpe
2020-05-13  6:26 ` [PATCH 12/33] tcp: add tcp_sock_set_quickack Christoph Hellwig
2020-05-13  6:26 ` [PATCH 13/33] tcp: add tcp_sock_set_syncnt Christoph Hellwig
2020-05-13  6:26 ` [PATCH 14/33] tcp: add tcp_sock_set_user_timeout Christoph Hellwig
2020-05-13  6:26 ` [PATCH 15/33] tcp: add tcp_sock_set_keepidle Christoph Hellwig
2020-05-13  6:26 ` [PATCH 16/33] tcp: add tcp_sock_set_keepintvl Christoph Hellwig
2020-05-13  6:26 ` [PATCH 17/33] tcp: add tcp_sock_set_keepcnt Christoph Hellwig
2020-05-13  6:26 ` [PATCH 18/33] ipv4: add ip_sock_set_tos Christoph Hellwig
2020-05-13  6:26 ` [PATCH 19/33] ipv4: add ip_sock_set_freebind Christoph Hellwig
2020-05-13  6:26 ` [PATCH 20/33] ipv4: add ip_sock_set_recverr Christoph Hellwig
2020-05-13 21:00   ` Joe Perches
2020-05-14 10:30     ` Christoph Hellwig
2020-05-14 11:51       ` Joe Perches
2020-05-20 14:18         ` Christoph Hellwig
2020-05-13  6:26 ` [PATCH 21/33] ipv4: add ip_sock_set_mtu_discover Christoph Hellwig
2020-05-13  6:26 ` [PATCH 22/33] ipv6: add ip6_sock_set_v6only Christoph Hellwig
2020-05-13  6:26 ` [PATCH 23/33] ipv6: add ip6_sock_set_recverr Christoph Hellwig
2020-05-13  6:26 ` [PATCH 24/33] ipv6: add ip6_sock_set_addr_preferences Christoph Hellwig
2020-05-13  6:26 ` [PATCH 25/33] ipv6: add ip6_sock_set_recvpktinfo Christoph Hellwig
2020-05-13  6:26 ` [PATCH 26/33] sctp: lift copying in addrs into sctp_setsockopt Christoph Hellwig
2020-05-13  6:26 ` [PATCH 27/33] sctp: export sctp_setsockopt_bindx Christoph Hellwig
2020-05-13 18:00   ` Marcelo Ricardo Leitner
2020-05-14  6:28     ` Christoph Hellwig
2020-05-14  8:23     ` David Laight
2020-05-14 10:40     ` is it ok to always pull in sctp for dlm, was: " Christoph Hellwig
2020-05-14 14:24       ` David Teigland
2020-05-15 15:20     ` David Howells
2020-05-15 15:24       ` Christoph Hellwig
2020-05-16 15:21         ` David Laight [this message]
2020-05-16 15:11       ` David Laight
2020-05-16 15:36         ` [Ocfs2-devel] " Matthew Wilcox
2020-05-17  8:48           ` David Laight
2020-05-13  6:26 ` [PATCH 28/33] sctp: add sctp_sock_set_nodelay Christoph Hellwig
2020-05-13  6:26 ` [PATCH 29/33] rxrpc_sock_set_min_security_level Christoph Hellwig
2020-05-13  6:26 ` [PATCH 30/33] tipc: call tsk_set_importance from tipc_topsrv_create_listener Christoph Hellwig
2020-05-13  6:26 ` [PATCH 31/33] net: remove kernel_setsockopt Christoph Hellwig
2020-05-13  6:26 ` [PATCH 32/33] sctp: add sctp_sock_get_primary_addr Christoph Hellwig
2020-05-13 18:03   ` Marcelo Ricardo Leitner
2020-05-14  9:51     ` David Laight
2020-05-14 12:30       ` David Laight
2020-05-14 13:27         ` David Laight
2020-05-13  6:26 ` [PATCH 33/33] net: remove kernel_getsockopt Christoph Hellwig
2020-05-13 13:13 ` [PATCH 29/33] rxrpc_sock_set_min_security_level David Howells
2020-05-14 10:29   ` Christoph Hellwig
2020-05-15 15:13   ` David Howells
2020-05-13 13:17 ` [PATCH 21/33] ipv4: add ip_sock_set_mtu_discover David Howells
2020-05-14  6:26   ` Christoph Hellwig
2020-05-15 15:15   ` David Howells
2020-05-13 13:24 ` [PATCH 20/33] ipv4: add ip_sock_set_recverr David Howells
2020-05-13 13:25 ` [PATCH 23/33] ipv6: add ip6_sock_set_recverr David Howells
2020-05-13 13:27 ` [PATCH 06/33] net: add sock_set_timestamps David Howells
2020-05-13 17:38 ` remove kernel_setsockopt and kernel_getsockopt Joe Perches
2020-05-14  6:27   ` Christoph Hellwig
2020-05-14  8:29   ` David Laight
2020-05-14 10:18     ` Christoph Hellwig
2020-05-14 10:26       ` David Laight
2020-05-14 10:34         ` 'Christoph Hellwig'
2020-05-14 11:11           ` David Laight
2020-05-14 19:35             ` [Ocfs2-devel] " Matthew Wilcox
2020-05-14 20:03         ` David Miller
2020-05-15  8:14           ` David Laight
2020-05-14 19:57     ` David Miller
2020-05-13 18:45 ` Sagi Grimberg
2020-05-13 19:12 ` David Miller

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