random: remove unneeded hash of a portion of the entropy pool

We previously extracted a portion of the entropy pool in
mix_pool_bytes() and hashed it in to avoid racing CPU's from returning
duplicate random values.  Now that we are using a spinlock to prevent
this from happening, this is no longer necessary.  So remove it, to
simplify the code a bit.

Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: George Spelvin <linux@horizon.com>

1 files changed, 20 insertions, 31 deletions

diff --git a/drivers/char/random.c b/drivers/char/random.c
index 922a2e4089f9..bc0de22f31f4 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -481,9 +481,9 @@ static __u32 const twist_table[8] = {
  * the entropy is concentrated in the low-order bits.
  */
 static void _mix_pool_bytes(struct entropy_store *r, const void *in,
-                            int nbytes, __u8 out[64])
+                            int nbytes)
 {
-        unsigned long i, j, tap1, tap2, tap3, tap4, tap5;
+        unsigned long i, tap1, tap2, tap3, tap4, tap5;
         int input_rotate;
         int wordmask = r->poolinfo->poolwords - 1;
         const char *bytes = in;
@@ -525,27 +525,23 @@ static void _mix_pool_bytes(struct entropy_store *r, const void *in,
 
         r->input_rotate = input_rotate;
         r->add_ptr = i;
-
-        if (out)
-                for (j = 0; j < 16; j++)
-                        ((__u32 *)out)[j] = r->pool[(i - j) & wordmask];
 }
 
 static void __mix_pool_bytes(struct entropy_store *r, const void *in,
-                             int nbytes, __u8 out[64])
+                             int nbytes)
 {
         trace_mix_pool_bytes_nolock(r->name, nbytes, _RET_IP_);
-        _mix_pool_bytes(r, in, nbytes, out);
+        _mix_pool_bytes(r, in, nbytes);
 }
 
 static void mix_pool_bytes(struct entropy_store *r, const void *in,
-                           int nbytes, __u8 out[64])
+                           int nbytes)
 {
         unsigned long flags;
 
         trace_mix_pool_bytes(r->name, nbytes, _RET_IP_);
         spin_lock_irqsave(&r->lock, flags);
-        _mix_pool_bytes(r, in, nbytes, out);
+        _mix_pool_bytes(r, in, nbytes);
         spin_unlock_irqrestore(&r->lock, flags);
 }
 
@@ -737,13 +733,13 @@ void add_device_randomness(const void *buf, unsigned int size)
 
         trace_add_device_randomness(size, _RET_IP_);
         spin_lock_irqsave(&input_pool.lock, flags);
-        _mix_pool_bytes(&input_pool, buf, size, NULL);
-        _mix_pool_bytes(&input_pool, &time, sizeof(time), NULL);
+        _mix_pool_bytes(&input_pool, buf, size);
+        _mix_pool_bytes(&input_pool, &time, sizeof(time));
         spin_unlock_irqrestore(&input_pool.lock, flags);
 
         spin_lock_irqsave(&nonblocking_pool.lock, flags);
-        _mix_pool_bytes(&nonblocking_pool, buf, size, NULL);
-        _mix_pool_bytes(&nonblocking_pool, &time, sizeof(time), NULL);
+        _mix_pool_bytes(&nonblocking_pool, buf, size);
+        _mix_pool_bytes(&nonblocking_pool, &time, sizeof(time));
         spin_unlock_irqrestore(&nonblocking_pool.lock, flags);
 }
 EXPORT_SYMBOL(add_device_randomness);
@@ -776,7 +772,7 @@ static void add_timer_randomness(struct timer_rand_state *state, unsigned num)
         sample.cycles = random_get_entropy();
         sample.num = num;
         r = nonblocking_pool.initialized ? &input_pool : &nonblocking_pool;
-        mix_pool_bytes(r, &sample, sizeof(sample), NULL);
+        mix_pool_bytes(r, &sample, sizeof(sample));
 
         /*
          * Calculate number of bits of randomness we probably added.
@@ -864,7 +860,7 @@ void add_interrupt_randomness(int irq, int irq_flags)
                 return;
         }
         fast_pool->last = now;
-        __mix_pool_bytes(r, &fast_pool->pool, sizeof(fast_pool->pool), NULL);
+        __mix_pool_bytes(r, &fast_pool->pool, sizeof(fast_pool->pool));
 
         /*
          * If we have architectural seed generator, produce a seed and
@@ -872,7 +868,7 @@ void add_interrupt_randomness(int irq, int irq_flags)
          * 50% entropic.
          */
         if (arch_get_random_seed_long(&seed)) {
-                __mix_pool_bytes(r, &seed, sizeof(seed), NULL);
+                __mix_pool_bytes(r, &seed, sizeof(seed));
                 credit += sizeof(seed) * 4;
         }
         spin_unlock(&r->lock);
@@ -955,7 +951,7 @@ static void _xfer_secondary_pool(struct entropy_store *r, size_t nbytes)
                                   ENTROPY_BITS(r), ENTROPY_BITS(r->pull));
         bytes = extract_entropy(r->pull, tmp, bytes,
                                 random_read_wakeup_bits / 8, rsvd_bytes);
-        mix_pool_bytes(r, tmp, bytes, NULL);
+        mix_pool_bytes(r, tmp, bytes);
         credit_entropy_bits(r, bytes*8);
 }
 
@@ -1031,7 +1027,6 @@ static void extract_buf(struct entropy_store *r, __u8 *out)
                 unsigned long l[LONGS(20)];
         } hash;
         __u32 workspace[SHA_WORKSPACE_WORDS];
-        __u8 extract[64];
         unsigned long flags;
 
         /*
@@ -1060,15 +1055,9 @@ static void extract_buf(struct entropy_store *r, __u8 *out)
          * brute-forcing the feedback as hard as brute-forcing the
          * hash.
          */
-        __mix_pool_bytes(r, hash.w, sizeof(hash.w), extract);
+        __mix_pool_bytes(r, hash.w, sizeof(hash.w));
         spin_unlock_irqrestore(&r->lock, flags);
 
-        /*
-         * To avoid duplicates, we atomically extract a portion of the
-         * pool while mixing, and hash one final time.
-         */
-        sha_transform(hash.w, extract, workspace);
-        memset(extract, 0, sizeof(extract));
         memset(workspace, 0, sizeof(workspace));
 
         /*
@@ -1255,14 +1244,14 @@ static void init_std_data(struct entropy_store *r)
         unsigned long rv;
 
         r->last_pulled = jiffies;
-        mix_pool_bytes(r, &now, sizeof(now), NULL);
+        mix_pool_bytes(r, &now, sizeof(now));
         for (i = r->poolinfo->poolbytes; i > 0; i -= sizeof(rv)) {
                 if (!arch_get_random_seed_long(&rv) &&
                     !arch_get_random_long(&rv))
                         rv = random_get_entropy();
-                mix_pool_bytes(r, &rv, sizeof(rv), NULL);
+                mix_pool_bytes(r, &rv, sizeof(rv));
         }
-        mix_pool_bytes(r, utsname(), sizeof(*(utsname())), NULL);
+        mix_pool_bytes(r, utsname(), sizeof(*(utsname())));
 }
 
 /*
@@ -1325,7 +1314,7 @@ static int arch_random_refill(void)
         if (n) {
                 unsigned int rand_bytes = n * sizeof(unsigned long);
 
-                mix_pool_bytes(&input_pool, buf, rand_bytes, NULL);
+                mix_pool_bytes(&input_pool, buf, rand_bytes);
                 credit_entropy_bits(&input_pool, rand_bytes*4);
         }
 
@@ -1415,7 +1404,7 @@ write_pool(struct entropy_store *r, const char __user *buffer, size_t count)
                 count -= bytes;
                 p += bytes;
 
-                mix_pool_bytes(r, buf, bytes, NULL);
+                mix_pool_bytes(r, buf, bytes);
                 cond_resched();
         }