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author | Jason A. Donenfeld <Jason@zx2c4.com> | 2022-04-14 02:50:38 +0300 |
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committer | Jason A. Donenfeld <Jason@zx2c4.com> | 2022-04-16 13:53:31 +0300 |
commit | 35a33ff3807d3adb9daaf937f5bca002ffa9f84e (patch) | |
tree | 801251338649869666b8cee5d34d2571b08c60a7 /drivers/char | |
parent | b0c3e796f24b588b862b61ce235d3c9417dc8983 (diff) | |
download | linux-35a33ff3807d3adb9daaf937f5bca002ffa9f84e.tar.xz |
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>
Diffstat (limited to 'drivers/char')
-rw-r--r-- | drivers/char/random.c | 2 |
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)); } |