Commit cf9f151c authored by Eric W. Biederman's avatar Eric W. Biederman Committed by Linus Torvalds
Browse files

[PATCH] sysctl: simplify sysctl_uts_string 



The binary interface to the namespace sysctls was never implemented resulting
in some really weird things if you attempted to use sys_sysctl to read your
hostname for example.

This patch series simples the code a little and implements the binary sysctl
interface.

In testing this patch series I discovered that our 32bit compatibility for the
binary sysctl interface is imperfect.  In particular KERN_SHMMAX and
KERN_SMMALL are size_t sized quantities and are returned as 8 bytes on to
32bit binaries using a x86_64 kernel.  However this has existing for a long
time so it is not a new regression with the namespace work.

Gads the whole sysctl thing needs work before it stops being easy to shoot
yourself in the foot.

Looking forward a little bit we need a better way to handle sysctls and
namespaces as our current technique will not work for the network namespace.
I think something based on the current overlapping sysctl trees will work but
the proc side needs to be redone before we can use it.

This patch:

Introduce get_uts() and put_uts() (used later) and remove most of the special
cases for when UTS namespace is compiled in.

Signed-off-by: default avatarEric W. Biederman <ebiederm@xmission.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 6b1b60f4

kernel/sysctl.c

+26 −102
Original line number Diff line number Diff line
@@ -163,6 +163,28 @@ extern ctl_table inotify_table[]; 
int sysctl_legacy_va_layout;

#endif



static void *get_uts(ctl_table *table, int write)

{

	char *which = table->data;

#ifdef CONFIG_UTS_NS

	struct uts_namespace *uts_ns = current->nsproxy->uts_ns;

	which = (which - (char *)&init_uts_ns) + (char *)uts_ns;

#endif

	if (!write)

		down_read(&uts_sem);

	else

		down_write(&uts_sem);

	return which;

}



static void put_uts(ctl_table *table, int write, void *which)

{

	if (!write)

		up_read(&uts_sem);

	else

		up_write(&uts_sem);

}



/* /proc declarations: */



#ifdef CONFIG_PROC_SYSCTL
@@ -229,7 +251,6 @@ static ctl_table root_table[] = { 
};



static ctl_table kern_table[] = {

#ifndef CONFIG_UTS_NS

	{

		.ctl_name	= KERN_OSTYPE,

		.procname	= "ostype",
@@ -275,54 +296,6 @@ static ctl_table kern_table[] = { 
		.proc_handler	= &proc_do_uts_string,

		.strategy	= &sysctl_string,

	},

#else  /* !CONFIG_UTS_NS */

	{

		.ctl_name	= KERN_OSTYPE,

		.procname	= "ostype",

		.data		= NULL,

		/* could maybe use __NEW_UTS_LEN here? */

		.maxlen		= FIELD_SIZEOF(struct new_utsname, sysname),

		.mode		= 0444,

		.proc_handler	= &proc_do_uts_string,

		.strategy	= &sysctl_string,

	},

	{

		.ctl_name	= KERN_OSRELEASE,

		.procname	= "osrelease",

		.data		= NULL,

		.maxlen		= FIELD_SIZEOF(struct new_utsname, release),

		.mode		= 0444,

		.proc_handler	= &proc_do_uts_string,

		.strategy	= &sysctl_string,

	},

	{

		.ctl_name	= KERN_VERSION,

		.procname	= "version",

		.data		= NULL,

		.maxlen		= FIELD_SIZEOF(struct new_utsname, version),

		.mode		= 0444,

		.proc_handler	= &proc_do_uts_string,

		.strategy	= &sysctl_string,

	},

	{

		.ctl_name	= KERN_NODENAME,

		.procname	= "hostname",

		.data		= NULL,

		.maxlen		= FIELD_SIZEOF(struct new_utsname, nodename),

		.mode		= 0644,

		.proc_handler	= &proc_do_uts_string,

		.strategy	= &sysctl_string,

	},

	{

		.ctl_name	= KERN_DOMAINNAME,

		.procname	= "domainname",

		.data		= NULL,

		.maxlen		= FIELD_SIZEOF(struct new_utsname, domainname),

		.mode		= 0644,

		.proc_handler	= &proc_do_uts_string,

		.strategy	= &sysctl_string,

	},

#endif /* !CONFIG_UTS_NS */

	{

		.ctl_name	= KERN_PANIC,

		.procname	= "panic",
@@ -1754,65 +1727,16 @@ int proc_dostring(ctl_table *table, int write, struct file *filp, 
 *	to observe. Should this be in kernel/sys.c ????

 */



#ifndef CONFIG_UTS_NS

static int proc_do_uts_string(ctl_table *table, int write, struct file *filp,

		  void __user *buffer, size_t *lenp, loff_t *ppos)

{

	int r;



	if (!write) {

		down_read(&uts_sem);

		r=proc_dostring(table,0,filp,buffer,lenp, ppos);

		up_read(&uts_sem);

	} else {

		down_write(&uts_sem);

		r=proc_dostring(table,1,filp,buffer,lenp, ppos);

		up_write(&uts_sem);

	}

	return r;

}

#else /* !CONFIG_UTS_NS */

static int proc_do_uts_string(ctl_table *table, int write, struct file *filp,

		  void __user *buffer, size_t *lenp, loff_t *ppos)

{

	int r;

	struct uts_namespace* uts_ns = current->nsproxy->uts_ns;

	char* which;



	switch (table->ctl_name) {

	case KERN_OSTYPE:

		which = uts_ns->name.sysname;

		break;

	case KERN_NODENAME:

		which = uts_ns->name.nodename;

		break;

	case KERN_OSRELEASE:

		which = uts_ns->name.release;

		break;

	case KERN_VERSION:

		which = uts_ns->name.version;

		break;

	case KERN_DOMAINNAME:

		which = uts_ns->name.domainname;

		break;

	default:

		r = -EINVAL;

		goto out;

	}



	if (!write) {

		down_read(&uts_sem);

		r=_proc_do_string(which,table->maxlen,0,filp,buffer,lenp, ppos);

		up_read(&uts_sem);

	} else {

		down_write(&uts_sem);

		r=_proc_do_string(which,table->maxlen,1,filp,buffer,lenp, ppos);

		up_write(&uts_sem);

	}

 out:

	void *which;

	which = get_uts(table, write);

	r = _proc_do_string(which, table->maxlen,write,filp,buffer,lenp, ppos);

	put_uts(table, write, which);

	return r;

}

#endif /* !CONFIG_UTS_NS */



static int do_proc_dointvec_conv(int *negp, unsigned long *lvalp,

				 int *valp,