[net] tipc: fix using smp_processor_id() in preemptible

[Tuong Lien]

The 'this_cpu_ptr()' is used to obtain the AEAD key' TFM on the current
CPU for encryption, however the execution can be preemptible since it's
actually user-space context, so the 'using smp_processor_id() in
preemptible' has been observed.

We fix the issue by using the 'get/put_cpu_ptr()' API which consists of
a 'preempt_disable()' instead.

Fixes: fc1b6d6de220 ("tipc: introduce TIPC encryption & authentication")
Acked-by: Jon Maloy <jma...@redhat.com>
Signed-off-by: Tuong Lien <tuong.t.l...@dektech.com.au>
---
 net/tipc/crypto.c | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/net/tipc/crypto.c b/net/tipc/crypto.c
index c38babaa4e57..7c523dc81575 100644
--- a/net/tipc/crypto.c
+++ b/net/tipc/crypto.c
@@ -326,7 +326,8 @@ static void tipc_aead_free(struct rcu_head *rp)
        if (aead->cloned) {
                tipc_aead_put(aead->cloned);
        } else {
-               head = *this_cpu_ptr(aead->tfm_entry);
+               head = *get_cpu_ptr(aead->tfm_entry);
+               put_cpu_ptr(aead->tfm_entry);
                list_for_each_entry_safe(tfm_entry, tmp, &head->list, list) {
                        crypto_free_aead(tfm_entry->tfm);
                        list_del(&tfm_entry->list);
@@ -399,10 +400,15 @@ static void tipc_aead_users_set(struct tipc_aead __rcu 
*aead, int val)
  */
 static struct crypto_aead *tipc_aead_tfm_next(struct tipc_aead *aead)
 {
-       struct tipc_tfm **tfm_entry = this_cpu_ptr(aead->tfm_entry);
+       struct tipc_tfm **tfm_entry;
+       struct crypto_aead *tfm;
 
+       tfm_entry = get_cpu_ptr(aead->tfm_entry);
        *tfm_entry = list_next_entry(*tfm_entry, list);
-       return (*tfm_entry)->tfm;
+       tfm = (*tfm_entry)->tfm;
+       put_cpu_ptr(tfm_entry);
+
+       return tfm;
 }
 
 /**
-- 
2.26.2