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random: zero buffer after reading entropy from userspace

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commit 7b5164fb1279bf0251371848e40bae646b59b3a8 upstream.

This buffer may contain entropic data that shouldn't stick around longer
than needed, so zero out the temporary buffer at the end of write_pool().

Reviewed-by: Dominik Brodowski <linux@dominikbrodowski.net>
Reviewed-by: Jann Horn <jannh@google.com>
Reviewed-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Jason A. Donenfeld 2022-02-09 18:42:13 +01:00 committed by Greg Kroah-Hartman
parent 63c1aae40a
commit bb63851c25
1 changed files with 8 additions and 3 deletions
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11
drivers/char/random.c
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@ -1336,19 +1336,24 @@ static __poll_t random_poll(struct file *file, poll_table *wait)
static int write_pool(const char __user *ubuf, size_t count)
{
size_t len;
int ret = 0;
u8 block[BLAKE2S_BLOCK_SIZE];
while (count) {
len = min(count, sizeof(block));
if (copy_from_user(block, ubuf, len))
return -EFAULT;
if (copy_from_user(block, ubuf, len)) {
ret = -EFAULT;
goto out;
}
count -= len;
ubuf += len;
mix_pool_bytes(block, len);
cond_resched();
}
return 0;
out:
memzero_explicit(block, sizeof(block));
return ret;
}
static ssize_t random_write(struct file *file, const char __user *buffer,