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xfrm: Provide API to register translator module

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Add a skeleton for xfrm_compat module and provide API to register it in
xfrm_state.ko. struct xfrm_translator will have function pointers to
translate messages received from 32-bit userspace or to be sent to it
from 64-bit kernel.
module_get()/module_put() are used instead of rcu_read_lock() as the
module will vmalloc() memory for translation.
The new API is registered with xfrm_state module, not with xfrm_user as
the former needs translator for user_policy set by setsockopt() and
xfrm_user already uses functions from xfrm_state.

Signed-off-by: Dmitry Safonov <dima@arista.com>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
This commit is contained in:
Dmitry Safonov 2020-09-21 15:36:51 +01:00 committed by Steffen Klassert
parent 02a20d4fef
commit c9e7c76d70
5 changed files with 119 additions and 0 deletions
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19
include/net/xfrm.h
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@ -2000,6 +2000,25 @@ static inline int xfrm_tunnel_check(struct sk_buff *skb, struct xfrm_state *x,
return 0;
}
struct xfrm_translator {
struct module *owner;
};
#if IS_ENABLED(CONFIG_XFRM_USER_COMPAT)
extern int xfrm_register_translator(struct xfrm_translator *xtr);
extern int xfrm_unregister_translator(struct xfrm_translator *xtr);
extern struct xfrm_translator *xfrm_get_translator(void);
extern void xfrm_put_translator(struct xfrm_translator *xtr);
#else
static inline struct xfrm_translator *xfrm_get_translator(void)
{
return NULL;
}
static inline void xfrm_put_translator(struct xfrm_translator *xtr)
{
}
#endif
#if IS_ENABLED(CONFIG_IPV6)
static inline bool xfrm6_local_dontfrag(const struct sock *sk)
{

10
net/xfrm/Kconfig
View File

@ -28,6 +28,16 @@ config XFRM_USER
If unsure, say Y.
config XFRM_USER_COMPAT
tristate "Compatible ABI support"
depends on XFRM_USER && COMPAT_FOR_U64_ALIGNMENT
select WANT_COMPAT_NETLINK_MESSAGES
help
Transformation(XFRM) user configuration interface like IPsec
used by compatible Linux applications.
If unsure, say N.
config XFRM_INTERFACE
tristate "Transformation virtual interface"
depends on XFRM && IPV6

1
net/xfrm/Makefile
View File

@ -9,6 +9,7 @@ obj-$(CONFIG_XFRM) := xfrm_policy.o xfrm_state.o xfrm_hash.o \
obj-$(CONFIG_XFRM_STATISTICS) += xfrm_proc.o
obj-$(CONFIG_XFRM_ALGO) += xfrm_algo.o
obj-$(CONFIG_XFRM_USER) += xfrm_user.o
obj-$(CONFIG_XFRM_USER_COMPAT) += xfrm_compat.o
obj-$(CONFIG_XFRM_IPCOMP) += xfrm_ipcomp.o
obj-$(CONFIG_XFRM_INTERFACE) += xfrm_interface.o
obj-$(CONFIG_XFRM_ESPINTCP) += espintcp.o

29
net/xfrm/xfrm_compat.c Normal file
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@ -0,0 +1,29 @@
// SPDX-License-Identifier: GPL-2.0
/*
* XFRM compat layer
* Author: Dmitry Safonov <dima@arista.com>
* Based on code and translator idea by: Florian Westphal <fw@strlen.de>
*/
#include <linux/compat.h>
#include <linux/xfrm.h>
#include <net/xfrm.h>
static struct xfrm_translator xfrm_translator = {
.owner = THIS_MODULE,
};
static int __init xfrm_compat_init(void)
{
return xfrm_register_translator(&xfrm_translator);
}
static void __exit xfrm_compat_exit(void)
{
xfrm_unregister_translator(&xfrm_translator);
}
module_init(xfrm_compat_init);
module_exit(xfrm_compat_exit);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Dmitry Safonov");
MODULE_DESCRIPTION("XFRM 32-bit compatibility layer");

60
net/xfrm/xfrm_state.c
View File

@ -2264,6 +2264,66 @@ static bool km_is_alive(const struct km_event *c)
return is_alive;
}
#if IS_ENABLED(CONFIG_XFRM_USER_COMPAT)
static DEFINE_SPINLOCK(xfrm_translator_lock);
static struct xfrm_translator __rcu *xfrm_translator;
struct xfrm_translator *xfrm_get_translator(void)
{
struct xfrm_translator *xtr;
rcu_read_lock();
xtr = rcu_dereference(xfrm_translator);
if (unlikely(!xtr))
goto out;
if (!try_module_get(xtr->owner))
xtr = NULL;
out:
rcu_read_unlock();
return xtr;
}
EXPORT_SYMBOL_GPL(xfrm_get_translator);
void xfrm_put_translator(struct xfrm_translator *xtr)
{
module_put(xtr->owner);
}
EXPORT_SYMBOL_GPL(xfrm_put_translator);
int xfrm_register_translator(struct xfrm_translator *xtr)
{
int err = 0;
spin_lock_bh(&xfrm_translator_lock);
if (unlikely(xfrm_translator != NULL))
err = -EEXIST;
else
rcu_assign_pointer(xfrm_translator, xtr);
spin_unlock_bh(&xfrm_translator_lock);
return err;
}
EXPORT_SYMBOL_GPL(xfrm_register_translator);
int xfrm_unregister_translator(struct xfrm_translator *xtr)
{
int err = 0;
spin_lock_bh(&xfrm_translator_lock);
if (likely(xfrm_translator != NULL)) {
if (rcu_access_pointer(xfrm_translator) != xtr)
err = -EINVAL;
else
RCU_INIT_POINTER(xfrm_translator, NULL);
}
spin_unlock_bh(&xfrm_translator_lock);
synchronize_rcu();
return err;
}
EXPORT_SYMBOL_GPL(xfrm_unregister_translator);
#endif
int xfrm_user_policy(struct sock *sk, int optname, sockptr_t optval, int optlen)
{
int err;