random: improve variable naming, clear extract buffer

- split the SHA variables apart into hash and workspace
- rename data to extract
- wipe extract and workspace after hashing

Signed-off-by: Matt Mackall <mpm@selenic.com>
Cc: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 13 insertions, 11 deletions

diff --git a/drivers/char/random.c b/drivers/char/random.c
index a2329a11e139..d125a4b792d0 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -765,9 +765,9 @@ static size_t account(struct entropy_store *r, size_t nbytes, int min,
 static void extract_buf(struct entropy_store *r, __u8 *out)
 {
         int i;
-        __u32 data[16], buf[5 + SHA_WORKSPACE_WORDS];
+        __u32 extract[16], hash[5], workspace[SHA_WORKSPACE_WORDS];
 
-        sha_init(buf);
+        sha_init(hash);
         /*
          * As we hash the pool, we mix intermediate values of
          * the hash back into the pool.  This eliminates
@@ -778,9 +778,9 @@ static void extract_buf(struct entropy_store *r, __u8 *out)
          */
         for (i = 0; i < r->poolinfo->poolwords; i += 16) {
                 /* hash blocks of 16 words = 512 bits */
-                sha_transform(buf, (__u8 *)(r->pool + i), buf + 5);
+                sha_transform(hash, (__u8 *)(r->pool + i), workspace);
                 /* feed back portion of the resulting hash */
-                add_entropy_words(r, &buf[i % 5], 1);
+                add_entropy_words(r, &hash[i % 5], 1);
         }
 
         /*
@@ -788,19 +788,21 @@ static void extract_buf(struct entropy_store *r, __u8 *out)
          * portion of the pool while mixing, and hash one
          * final time.
          */
-        __add_entropy_words(r, &buf[i % 5], 1, data);
-        sha_transform(buf, (__u8 *)data, buf + 5);
+        __add_entropy_words(r, &hash[i % 5], 1, extract);
+        sha_transform(hash, (__u8 *)extract, workspace);
+        memset(extract, 0, sizeof(extract));
+        memset(workspace, 0, sizeof(workspace));
 
         /*
          * In case the hash function has some recognizable
          * output pattern, we fold it in half.
          */
 
-        buf[0] ^= buf[3];
-        buf[1] ^= buf[4];
-        buf[2] ^= rol32(buf[2], 16);
-        memcpy(out, buf, EXTRACT_SIZE);
-        memset(buf, 0, sizeof(buf));
+        hash[0] ^= hash[3];
+        hash[1] ^= hash[4];
+        hash[2] ^= rol32(hash[2], 16);
+        memcpy(out, hash, EXTRACT_SIZE);
+        memset(hash, 0, sizeof(hash));
 }
 
 static ssize_t extract_entropy(struct entropy_store *r, void *buf,