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authorJason A. Donenfeld <Jason@zx2c4.com>2022-04-14 01:50:38 +0200
committerJason A. Donenfeld <Jason@zx2c4.com>2022-04-16 12:53:31 +0200
commit35a33ff3807d3adb9daaf937f5bca002ffa9f84e (patch)
tree801251338649869666b8cee5d34d2571b08c60a7
parentb0c3e796f24b588b862b61ce235d3c9417dc8983 (diff)
downloadlinux-35a33ff3807d3adb9daaf937f5bca002ffa9f84e.tar.bz2
random: use memmove instead of memcpy for remaining 32 bytes
In order to immediately overwrite the old key on the stack, before servicing a userspace request for bytes, we use the remaining 32 bytes of block 0 as the key. This means moving indices 8,9,a,b,c,d,e,f -> 4,5,6,7,8,9,a,b. Since 4 < 8, for the kernel implementations of memcpy(), this doesn't actually appear to be a problem in practice. But relying on that characteristic seems a bit brittle. So let's change that to a proper memmove(), which is the by-the-books way of handling overlapping memory copies. Reviewed-by: Dominik Brodowski <linux@dominikbrodowski.net> Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
-rw-r--r--drivers/char/random.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/drivers/char/random.c b/drivers/char/random.c
index 6b01b2be9dd4..3a293f919af9 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -333,7 +333,7 @@ static void crng_fast_key_erasure(u8 key[CHACHA_KEY_SIZE],
chacha20_block(chacha_state, first_block);
memcpy(key, first_block, CHACHA_KEY_SIZE);
- memcpy(random_data, first_block + CHACHA_KEY_SIZE, random_data_len);
+ memmove(random_data, first_block + CHACHA_KEY_SIZE, random_data_len);
memzero_explicit(first_block, sizeof(first_block));
}