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Subject[PATCH v3 1/7] xfrm: Provide API to register translator module
Date
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>
---
include/net/xfrm.h | 19 +++++++++++++
net/xfrm/Kconfig | 10 +++++++
net/xfrm/Makefile | 1 +
net/xfrm/xfrm_compat.c | 29 ++++++++++++++++++++
net/xfrm/xfrm_state.c | 60 ++++++++++++++++++++++++++++++++++++++++++
5 files changed, 119 insertions(+)
create mode 100644 net/xfrm/xfrm_compat.c

diff --git a/include/net/xfrm.h b/include/net/xfrm.h
index 2737d24ec244..fe2e3717da14 100644
--- a/include/net/xfrm.h
+++ b/include/net/xfrm.h
@@ -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)
{
diff --git a/net/xfrm/Kconfig b/net/xfrm/Kconfig
index 5b9a5ab48111..e79b48dab61b 100644
--- a/net/xfrm/Kconfig
+++ b/net/xfrm/Kconfig
@@ -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
diff --git a/net/xfrm/Makefile b/net/xfrm/Makefile
index 2d4bb4b9f75e..494aa744bfb9 100644
--- a/net/xfrm/Makefile
+++ b/net/xfrm/Makefile
@@ -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
diff --git a/net/xfrm/xfrm_compat.c b/net/xfrm/xfrm_compat.c
new file mode 100644
index 000000000000..f01d9af41c55
--- /dev/null
+++ b/net/xfrm/xfrm_compat.c
@@ -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");
diff --git a/net/xfrm/xfrm_state.c b/net/xfrm/xfrm_state.c
index 69520ad3d83b..cc206ca3df78 100644
--- a/net/xfrm/xfrm_state.c
+++ b/net/xfrm/xfrm_state.c
@@ -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;
--
2.28.0
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