In 79a8468747c5 ("random: check for increase of entropy_count because of
signed conversion"), a number of checks were added around what values
were passed to account(), because account() was doing fancy fixed point
fractional arithmetic, and a user had some ability to pass large values
directly into it. One of things in that commit was limiting those values
to INT_MAX >> 6.
However, for several years now, urandom reads no longer touch entropy
accounting, and so this check serves no purpose. The current flow is:
urandom_read_nowarn()-->get_random_bytes_user()-->chacha20_block()
We arrive at urandom_read_nowarn() in the first place either via
ordinary fops, which limits reads to MAX_RW_COUNT, or via getrandom()
which limits reads to INT_MAX.
Cc: Theodore Ts'o <tytso@xxxxxxx>
Cc: Dominik Brodowski <linux@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Jason A. Donenfeld <Jason@xxxxxxxxx>
---
drivers/char/random.c | 1 -
1 file changed, 1 deletion(-)
diff --git a/drivers/char/random.c b/drivers/char/random.c
index ac22dc94b037..fa366ab38263 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -1324,7 +1324,6 @@ static ssize_t urandom_read_nowarn(struct file *file, char __user *buf,
{
int ret;
- nbytes = min_t(size_t, nbytes, INT_MAX >> 6);
ret = get_random_bytes_user(buf, nbytes);
trace_urandom_read(8 * nbytes, 0, input_pool.entropy_count);
return ret;
--
2.35.0
