Commit 27df6f25 authored Aug 31, 2008 by Cyrill Gorcunov Committed by J. Bruce Fields Sep 01, 2008

sunrpc: fix possible overrun on read of /proc/sys/sunrpc/transports



Vegard Nossum reported
----------------------
> I noticed that something weird is going on with /proc/sys/sunrpc/transports.
> This file is generated in net/sunrpc/sysctl.c, function proc_do_xprt(). When
> I "cat" this file, I get the expected output:
>    $ cat /proc/sys/sunrpc/transports
>    tcp 1048576
>    udp 32768

> But I think that it does not check the length of the buffer supplied by
> userspace to read(). With my original program, I found that the stack was
> being overwritten by the characters above, even when the length given to
> read() was just 1.

David Wagner added (among other things) that copy_to_user could be
probably used here.

Ingo Oeser suggested to use simple_read_from_buffer() here.

The conclusion is that proc_do_xprt doesn't check for userside buffer
size indeed so fix this by using Ingo's suggestion.

Reported-by: Vegard Nossum <vegard.nossum@gmail.com>
Signed-off-by: Cyrill Gorcunov <gorcunov@gmail.com>
CC: Ingo Oeser <ioe-lkml@rameria.de>
Cc: Neil Brown <neilb@suse.de>
Cc: Chuck Lever <chuck.lever@oracle.com>
Cc: Greg Banks <gnb@sgi.com>
Cc: Tom Tucker <tom@opengridcomputing.com>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>

parent c228c24b

net/sunrpc/sysctl.c

+4 −14

Original line number	Original line	Diff line number	Diff line
	@@ -60,24 +60,14 @@ static int proc_do_xprt(ctl_table table, int write, struct file file,
	void __user buffer, size_t lenp, loff_t *ppos)		void __user buffer, size_t lenp, loff_t *ppos)
	{		{
	char tmpbuf[256];		char tmpbuf[256];
	int len;		size_t len;

	if ((ppos && !write) \|\| !lenp) {		if ((ppos && !write) \|\| !lenp) {
	*lenp = 0;		*lenp = 0;
	return 0;		return 0;
	}		}
	if (write)
	return -EINVAL;
	else {
	len = svc_print_xprts(tmpbuf, sizeof(tmpbuf));		len = svc_print_xprts(tmpbuf, sizeof(tmpbuf));
	if (!access_ok(VERIFY_WRITE, buffer, len))		return simple_read_from_buffer(buffer, *lenp, ppos, tmpbuf, len);
	return -EFAULT;

	if (__copy_to_user(buffer, tmpbuf, len))
	return -EFAULT;
	}
	*lenp -= len;
	*ppos += len;
	return 0;
	}		}

	static int		static int