random: simplify fips mode

commit e954bc91 upstream.

Rather than dynamically allocate 10 bytes, move it to static allocation.
This saves space and avoids the need for error checking.
Signed-off-by: Matt Mackall <mpm@selenic.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
[PG: adding this simplifies required updates to random for .34 stable]
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: Willy Tarreau <w@1wt.eu>

drivers/char/random.c

@@ -264,6 +264,7 @@
 #define INPUT_POOL_WORDS 128
 #define OUTPUT_POOL_WORDS 32
 #define SEC_XFER_SIZE 512
+#define EXTRACT_SIZE 10
 
 /*
  * The minimum number of bits of entropy before we wake up a read on
@@ -421,7 +422,7 @@ struct entropy_store {
 	unsigned add_ptr;
 	int entropy_count;
 	int input_rotate;
-	__u8 *last_data;
+	__u8 last_data[EXTRACT_SIZE];
 };
 
 static __u32 input_pool_data[INPUT_POOL_WORDS];
@@ -721,8 +722,6 @@ void add_disk_randomness(struct gendisk *disk)
 }
 #endif
 
-#define EXTRACT_SIZE 10
-
 /*********************************************************************
  *
  * Entropy extraction routines
@@ -869,7 +868,7 @@ static ssize_t extract_entropy(struct entropy_store *r, void *buf,
 	while (nbytes) {
 		extract_buf(r, tmp);
 
-		if (r->last_data) {
+		if (fips_enabled) {
 			spin_lock_irqsave(&r->lock, flags);
 			if (!memcmp(tmp, r->last_data, EXTRACT_SIZE))
 				panic("Hardware RNG duplicated output!\n");
@@ -958,9 +957,6 @@ static void init_std_data(struct entropy_store *r)
 	now = ktime_get_real();
 	mix_pool_bytes(r, &now, sizeof(now));
 	mix_pool_bytes(r, utsname(), sizeof(*(utsname())));
-	/* Enable continuous test in fips mode */
-	if (fips_enabled)
-		r->last_data = kmalloc(EXTRACT_SIZE, GFP_KERNEL);
 }
 
 static int rand_initialize(void)