crypto: chacha20 - Fix chacha20_block() keystream alignment (again)

In commit 9f480faec58c ("crypto: chacha20 - Fix keystream alignment for
chacha20_block()"), I had missed that chacha20_block() can be called
directly on the buffer passed to get_random_bytes(), which can have any
alignment.  So, while my commit didn't break anything, it didn't fully
solve the alignment problems.

Revert my solution and just update chacha20_block() to use
put_unaligned_le32(), so the output buffer need not be aligned.
This is simpler, and on many CPUs it's the same speed.

But, I kept the 'tmp' buffers in extract_crng_user() and
_get_random_bytes() 4-byte aligned, since that alignment is actually
needed for _crng_backtrack_protect() too.

Reported-by: Stephan Müller <smueller@chronox.de>
Cc: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

1 files changed, 12 insertions, 12 deletions

diff --git a/drivers/char/random.c b/drivers/char/random.c
index bf5f99fc36f1..d22d967c50f0 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -433,9 +433,9 @@ static int crng_init_cnt = 0;
 static unsigned long crng_global_init_time = 0;
 #define CRNG_INIT_CNT_THRESH (2*CHACHA20_KEY_SIZE)
 static void _extract_crng(struct crng_state *crng,
-                          __u32 out[CHACHA20_BLOCK_WORDS]);
+                          __u8 out[CHACHA20_BLOCK_SIZE]);
 static void _crng_backtrack_protect(struct crng_state *crng,
-                                    __u32 tmp[CHACHA20_BLOCK_WORDS], int used);
+                                    __u8 tmp[CHACHA20_BLOCK_SIZE], int used);
 static void process_random_ready_list(void);
 static void _get_random_bytes(void *buf, int nbytes);
 
@@ -921,7 +921,7 @@ static void crng_reseed(struct crng_state *crng, struct entropy_store *r)
         unsigned long   flags;
         int             i, num;
         union {
-                __u32   block[CHACHA20_BLOCK_WORDS];
+                __u8    block[CHACHA20_BLOCK_SIZE];
                 __u32   key[8];
         } buf;
 
@@ -968,7 +968,7 @@ static void crng_reseed(struct crng_state *crng, struct entropy_store *r)
 }
 
 static void _extract_crng(struct crng_state *crng,
-                          __u32 out[CHACHA20_BLOCK_WORDS])
+                          __u8 out[CHACHA20_BLOCK_SIZE])
 {
         unsigned long v, flags;
 
@@ -985,7 +985,7 @@ static void _extract_crng(struct crng_state *crng,
         spin_unlock_irqrestore(&crng->lock, flags);
 }
 
-static void extract_crng(__u32 out[CHACHA20_BLOCK_WORDS])
+static void extract_crng(__u8 out[CHACHA20_BLOCK_SIZE])
 {
         struct crng_state *crng = NULL;
 
@@ -1003,7 +1003,7 @@ static void extract_crng(__u32 out[CHACHA20_BLOCK_WORDS])
  * enough) to mutate the CRNG key to provide backtracking protection.
  */
 static void _crng_backtrack_protect(struct crng_state *crng,
-                                    __u32 tmp[CHACHA20_BLOCK_WORDS], int used)
+                                    __u8 tmp[CHACHA20_BLOCK_SIZE], int used)
 {
         unsigned long   flags;
         __u32           *s, *d;
@@ -1015,14 +1015,14 @@ static void _crng_backtrack_protect(struct crng_state *crng,
                 used = 0;
         }
         spin_lock_irqsave(&crng->lock, flags);
-        s = &tmp[used / sizeof(__u32)];
+        s = (__u32 *) &tmp[used];
         d = &crng->state[4];
         for (i=0; i < 8; i++)
                 *d++ ^= *s++;
         spin_unlock_irqrestore(&crng->lock, flags);
 }
 
-static void crng_backtrack_protect(__u32 tmp[CHACHA20_BLOCK_WORDS], int used)
+static void crng_backtrack_protect(__u8 tmp[CHACHA20_BLOCK_SIZE], int used)
 {
         struct crng_state *crng = NULL;
 
@@ -1038,7 +1038,7 @@ static void crng_backtrack_protect(__u32 tmp[CHACHA20_BLOCK_WORDS], int used)
 static ssize_t extract_crng_user(void __user *buf, size_t nbytes)
 {
         ssize_t ret = 0, i = CHACHA20_BLOCK_SIZE;
-        __u32 tmp[CHACHA20_BLOCK_WORDS];
+        __u8 tmp[CHACHA20_BLOCK_SIZE] __aligned(4);
         int large_request = (nbytes > 256);
 
         while (nbytes) {
@@ -1617,7 +1617,7 @@ static void _warn_unseeded_randomness(const char *func_name, void *caller,
  */
 static void _get_random_bytes(void *buf, int nbytes)
 {
-        __u32 tmp[CHACHA20_BLOCK_WORDS];
+        __u8 tmp[CHACHA20_BLOCK_SIZE] __aligned(4);
 
         trace_get_random_bytes(nbytes, _RET_IP_);
 
@@ -2243,7 +2243,7 @@ u64 get_random_u64(void)
         if (use_lock)
                 read_lock_irqsave(&batched_entropy_reset_lock, flags);
         if (batch->position % ARRAY_SIZE(batch->entropy_u64) == 0) {
-                extract_crng((__u32 *)batch->entropy_u64);
+                extract_crng((u8 *)batch->entropy_u64);
                 batch->position = 0;
         }
         ret = batch->entropy_u64[batch->position++];
@@ -2273,7 +2273,7 @@ u32 get_random_u32(void)
         if (use_lock)
                 read_lock_irqsave(&batched_entropy_reset_lock, flags);
         if (batch->position % ARRAY_SIZE(batch->entropy_u32) == 0) {
-                extract_crng(batch->entropy_u32);
+                extract_crng((u8 *)batch->entropy_u32);
                 batch->position = 0;
         }
         ret = batch->entropy_u32[batch->position++];