From: Eric Dumazet <dada1@cosmosbay•com>
To: Evgeniy Polyakov <johnpol@2ka•mipt.ru>
Cc: David Miller <davem@davemloft•net>,
axboe@kernel•dk, netdev@vger•kernel.org
Subject: Re: Fix for the fundamental network/block layer race in sendfile().
Date: Tue, 01 Apr 2008 21:21:19 +0200 [thread overview]
Message-ID: <47F28B2F.2070609@cosmosbay.com> (raw)
In-Reply-To: <20080401180751.GA3263@2ka.mipt.ru>
Evgeniy Polyakov a écrit :
> On Tue, Apr 01, 2008 at 09:47:59PM +0400, Evgeniy Polyakov (johnpol@2ka•mipt.ru) wrote:
>>> 1) Is out_file garanted to be a socket ?
>>> 2) SO_PRIVATE_CALLBACK is defined to be 37 later on your patch. Is ORing 37
>>> to sk_flags really working ???
>>> 3) So, once a socket has been used for a sendfile(), all subsequent
>>> sendmsg() will call skb_splice_destructor ? (I see no clearing of
>>> SO_PRIVATE_CALLBACK)
>>> This will probably crash.
>>> 4) god_blessed_us name ... Oh I got it, its April the first !!!!
>
> Addressed all above (2 and 3 actually).
> The formed by using correct socket flag (set_bit/clear_bit, like in a
> real life), the latter by clearing bit on sendfile() exit and to fix
> exit/clear race each spliced page also setups lru.prev to itself, which
> is checked in destructor.
> Name was not changed, does it matter?
>
> Patch still works ok :)
>
> Thanks Eric for pointing that bugs.
>
> Signed-off-as-usual.
>
> diff --git a/fs/read_write.c b/fs/read_write.c
> index 49a9871..fda55f6 100644
> --- a/fs/read_write.c
> +++ b/fs/read_write.c
> @@ -16,6 +16,7 @@
> #include <linux/syscalls.h>
> #include <linux/pagemap.h>
> #include <linux/splice.h>
> +#include <net/sock.h>
> #include "read_write.h"
>
> #include <asm/uaccess.h>
> @@ -703,6 +704,8 @@ static ssize_t do_sendfile(int out_fd, int in_fd, loff_t *ppos,
> loff_t pos;
> ssize_t retval;
> int fput_needed_in, fput_needed_out, fl;
> + struct sock *sk;
> + struct socket *sock;
>
> /*
> * Get input file, and verify that it is ok..
> @@ -762,6 +765,12 @@ static ssize_t do_sendfile(int out_fd, int in_fd, loff_t *ppos,
> count = max - pos;
> }
>
> + sock = out_file->private_data;
> + sk = sock->sk;
> +
> + sk->sk_user_data = &skb_splice_destructor;
> + set_bit(SOCK_PRIVATE_CALLBACK, &sock->flags);
> +
> fl = 0;
> #if 0
> /*
> @@ -775,6 +784,8 @@ static ssize_t do_sendfile(int out_fd, int in_fd, loff_t *ppos,
> #endif
> retval = do_splice_direct(in_file, ppos, out_file, count, fl);
>
> + clear_bit(SOCK_PRIVATE_CALLBACK, &sock->flags);
I see no socket locking, so multiple threads could use sendfile() & sendmsg()
on same socket, and crash kernel...
next prev parent reply other threads:[~2008-04-01 19:21 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-03-28 9:20 Network/block layer race Evgeniy Polyakov
2008-03-28 20:40 ` David Miller
2008-03-28 20:56 ` Evgeniy Polyakov
2008-03-28 21:07 ` David Miller
2008-03-28 21:51 ` Evgeniy Polyakov
2008-04-01 16:49 ` Fix for the fundamental network/block layer race in sendfile() Evgeniy Polyakov
2008-04-01 17:14 ` Mika Penttilä
2008-04-01 17:36 ` Evgeniy Polyakov
2008-04-01 17:19 ` Eric Dumazet
2008-04-01 17:47 ` Evgeniy Polyakov
2008-04-01 18:07 ` Evgeniy Polyakov
2008-04-01 19:21 ` Eric Dumazet [this message]
2008-04-01 19:45 ` Evgeniy Polyakov
2008-04-01 20:59 ` Eric Dumazet
2008-04-01 21:14 ` Evgeniy Polyakov
2008-04-08 12:25 ` [take 2] " Evgeniy Polyakov
2008-04-08 12:58 ` Eric Dumazet
2008-04-08 17:26 ` Evgeniy Polyakov
2008-04-08 21:30 ` Evgeniy Polyakov
2008-04-09 11:33 ` Jens Axboe
2011-06-06 16:29 ` IPv6 DNSSL (rfc6106): please include the patch to pass it to user space Carlos Carvalho
2011-06-06 19:40 ` David Miller
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