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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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60
net/xfrm/xfrm_state.c
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@@ -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;