1 files changed, 15 insertions, 11 deletions

diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index 30c0cb8cc9bc..23920c5ff728 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -1669,19 +1669,22 @@ char *pointer_string(char *buf, char *end, const void *ptr,
         return number(buf, end, (unsigned long int)ptr, spec);
 }
 
-static bool have_filled_random_ptr_key __read_mostly;
+static DEFINE_STATIC_KEY_TRUE(not_filled_random_ptr_key);
 static siphash_key_t ptr_key __read_mostly;
 
-static void fill_random_ptr_key(struct random_ready_callback *unused)
+static void enable_ptr_key_workfn(struct work_struct *work)
 {
         get_random_bytes(&ptr_key, sizeof(ptr_key));
-        /*
-         * have_filled_random_ptr_key==true is dependent on get_random_bytes().
-         * ptr_to_id() needs to see have_filled_random_ptr_key==true
-         * after get_random_bytes() returns.
-         */
-        smp_mb();
-        WRITE_ONCE(have_filled_random_ptr_key, true);
+        /* Needs to run from preemptible context */
+        static_branch_disable(&not_filled_random_ptr_key);
+}
+
+static DECLARE_WORK(enable_ptr_key_work, enable_ptr_key_workfn);
+
+static void fill_random_ptr_key(struct random_ready_callback *unused)
+{
+        /* This may be in an interrupt handler. */
+        queue_work(system_unbound_wq, &enable_ptr_key_work);
 }
 
 static struct random_ready_callback random_ready = {
@@ -1695,7 +1698,8 @@ static int __init initialize_ptr_random(void)
         if (!ret) {
                 return 0;
         } else if (ret == -EALREADY) {
-                fill_random_ptr_key(&random_ready);
+                /* This is in preemptible context */
+                enable_ptr_key_workfn(&enable_ptr_key_work);
                 return 0;
         }
 
@@ -1709,7 +1713,7 @@ static char *ptr_to_id(char *buf, char *end, void *ptr, struct printf_spec spec)
         unsigned long hashval;
         const int default_width = 2 * sizeof(ptr);
 
-        if (unlikely(!have_filled_random_ptr_key)) {
+        if (static_branch_unlikely(&not_filled_random_ptr_key)) {
                 spec.field_width = default_width;
                 /* string length must be less than default_width */
                 return string(buf, end, "(ptrval)", spec);