Merge tag 'random_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/random

Pull random updates from Ted Ts'o:
 "Some changes to trust cpu-based hwrng (such as RDRAND) for
  initializing hashed pointers and (optionally, controlled by a config
  option) to initialize the CRNG to avoid boot hangs"

* tag 'random_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/random:
  random: Make crng state queryable
  random: remove preempt disabled region
  random: add a config option to trust the CPU's hwrng
  vsprintf: Add command line option debug_boot_weak_hash
  vsprintf: Use hw RNG for ptr_key
  random: Return nbytes filled from hw RNG
  random: Fix whitespace pre random-bytes work

1 files changed, 26 insertions, 1 deletions

diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index cda186230287..d5b3a3f95c01 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -1651,6 +1651,17 @@ char *device_node_string(char *buf, char *end, struct device_node *dn,
         return widen_string(buf, buf - buf_start, end, spec);
 }
 
+/* Make pointers available for printing early in the boot sequence. */
+static int debug_boot_weak_hash __ro_after_init;
+
+static int __init debug_boot_weak_hash_enable(char *str)
+{
+        debug_boot_weak_hash = 1;
+        pr_info("debug_boot_weak_hash enabled\n");
+        return 0;
+}
+early_param("debug_boot_weak_hash", debug_boot_weak_hash_enable);
+
 static DEFINE_STATIC_KEY_TRUE(not_filled_random_ptr_key);
 static siphash_key_t ptr_key __read_mostly;
 
@@ -1675,8 +1686,16 @@ static struct random_ready_callback random_ready = {
 
 static int __init initialize_ptr_random(void)
 {
-        int ret = add_random_ready_callback(&random_ready);
+        int key_size = sizeof(ptr_key);
+        int ret;
 
+        /* Use hw RNG if available. */
+        if (get_random_bytes_arch(&ptr_key, key_size) == key_size) {
+                static_branch_disable(&not_filled_random_ptr_key);
+                return 0;
+        }
+
+        ret = add_random_ready_callback(&random_ready);
         if (!ret) {
                 return 0;
         } else if (ret == -EALREADY) {
@@ -1695,6 +1714,12 @@ static char *ptr_to_id(char *buf, char *end, void *ptr, struct printf_spec spec)
         const char *str = sizeof(ptr) == 8 ? "(____ptrval____)" : "(ptrval)";
         unsigned long hashval;
 
+        /* When debugging early boot use non-cryptographically secure hash. */
+        if (unlikely(debug_boot_weak_hash)) {
+                hashval = hash_long((unsigned long)ptr, 32);
+                return pointer_string(buf, end, (const void *)hashval, spec);
+        }
+
         if (static_branch_unlikely(&not_filled_random_ptr_key)) {
                 spec.field_width = 2 * sizeof(ptr);
                 /* string length must be less than default_width */