1 files changed, 25 insertions, 10 deletions

diff --git a/crypto/ansi_cprng.c b/crypto/ansi_cprng.c
index 72db0fd763cc..0fac8ffc2fb7 100644
--- a/crypto/ansi_cprng.c
+++ b/crypto/ansi_cprng.c
@@ -161,7 +161,7 @@ static int _get_more_prng_bytes(struct prng_context *ctx)
         /*
          * Now update our DT value
          */
-        for (i = 0; i < DEFAULT_BLK_SZ; i++) {
+        for (i = DEFAULT_BLK_SZ - 1; i >= 0; i--) {
                 ctx->DT[i] += 1;
                 if (ctx->DT[i] != 0)
                         break;
@@ -223,9 +223,10 @@ remainder:
         }
 
         /*
-         * Copy up to the next whole block size
+         * Copy any data less than an entire block
          */
         if (byte_count < DEFAULT_BLK_SZ) {
+empty_rbuf:
                 for (; ctx->rand_data_valid < DEFAULT_BLK_SZ;
                         ctx->rand_data_valid++) {
                         *ptr = ctx->rand_data[ctx->rand_data_valid];
@@ -240,18 +241,22 @@ remainder:
          * Now copy whole blocks
          */
         for (; byte_count >= DEFAULT_BLK_SZ; byte_count -= DEFAULT_BLK_SZ) {
-                if (_get_more_prng_bytes(ctx) < 0) {
-                        memset(buf, 0, nbytes);
-                        err = -EINVAL;
-                        goto done;
+                if (ctx->rand_data_valid == DEFAULT_BLK_SZ) {
+                        if (_get_more_prng_bytes(ctx) < 0) {
+                                memset(buf, 0, nbytes);
+                                err = -EINVAL;
+                                goto done;
+                        }
                 }
+                if (ctx->rand_data_valid > 0)
+                        goto empty_rbuf;
                 memcpy(ptr, ctx->rand_data, DEFAULT_BLK_SZ);
                 ctx->rand_data_valid += DEFAULT_BLK_SZ;
                 ptr += DEFAULT_BLK_SZ;
         }
 
         /*
-         * Now copy any extra partial data
+         * Now go back and get any remaining partial block
          */
         if (byte_count)
                 goto remainder;
@@ -349,15 +354,25 @@ static int cprng_get_random(struct crypto_rng *tfm, u8 *rdata,
         return get_prng_bytes(rdata, dlen, prng);
 }
 
+/*
+ *  This is the cprng_registered reset method the seed value is
+ *  interpreted as the tuple { V KEY DT}
+ *  V and KEY are required during reset, and DT is optional, detected
+ *  as being present by testing the length of the seed
+ */
 static int cprng_reset(struct crypto_rng *tfm, u8 *seed, unsigned int slen)
 {
         struct prng_context *prng = crypto_rng_ctx(tfm);
-        u8 *key = seed + DEFAULT_PRNG_KSZ;
+        u8 *key = seed + DEFAULT_BLK_SZ;
+        u8 *dt = NULL;
 
         if (slen < DEFAULT_PRNG_KSZ + DEFAULT_BLK_SZ)
                 return -EINVAL;
 
-        reset_prng_context(prng, key, DEFAULT_PRNG_KSZ, seed, NULL);
+        if (slen >= (2 * DEFAULT_BLK_SZ + DEFAULT_PRNG_KSZ))
+                dt = key + DEFAULT_PRNG_KSZ;
+
+        reset_prng_context(prng, key, DEFAULT_PRNG_KSZ, seed, dt);
 
         if (prng->flags & PRNG_NEED_RESET)
                 return -EINVAL;
@@ -379,7 +394,7 @@ static struct crypto_alg rng_alg = {
                 .rng = {
                         .rng_make_random        = cprng_get_random,
                         .rng_reset              = cprng_reset,
-                        .seedsize = DEFAULT_PRNG_KSZ + DEFAULT_BLK_SZ,
+                        .seedsize = DEFAULT_PRNG_KSZ + 2*DEFAULT_BLK_SZ,
                 }
         }
 };