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random: Add a urandom_read_nowait() for random APIs that don't warn

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commit c6f1deb158 upstream.

/dev/random and getrandom() never warn.  Split the meat of
urandom_read() into urandom_read_nowarn() and leave the warning code
in urandom_read().

This has no effect on kernel behavior, but it makes subsequent
patches more straightforward.  It also makes the fact that
getrandom() never warns more obvious.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Link: https://lore.kernel.org/r/c87ab200588de746431d9f916501ef11e5242b13.1577088521.git.luto@kernel.org
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Andy Lutomirski
2019-12-23 00:20:45 -08:00
committed by Chris
parent 71bfb8ffc3
commit 122331b432
1 changed files with 15 additions and 6 deletions
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21
drivers/char/random.c
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@@ -1962,12 +1962,23 @@ random_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
return _random_read(file->f_flags & O_NONBLOCK, buf, nbytes);
}
static ssize_t
urandom_read_nowarn(struct file *file, char __user *buf, size_t nbytes,
loff_t *ppos)
{
int ret;
nbytes = min_t(size_t, nbytes, INT_MAX >> (ENTROPY_SHIFT + 3));
ret = extract_crng_user(buf, nbytes);
trace_urandom_read(8 * nbytes, 0, ENTROPY_BITS(&input_pool));
return ret;
}
static ssize_t
urandom_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
{
unsigned long flags;
static int maxwarn = 10;
int ret;
if (!crng_ready() && maxwarn > 0) {
maxwarn--;
@@ -1979,10 +1990,8 @@ urandom_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
crng_init_cnt = 0;
spin_unlock_irqrestore(&primary_crng.lock, flags);
}
nbytes = min_t(size_t, nbytes, INT_MAX >> (ENTROPY_SHIFT + 3));
ret = extract_crng_user(buf, nbytes);
trace_urandom_read(8 * nbytes, 0, ENTROPY_BITS(&input_pool));
return ret;
return urandom_read_nowarn(file, buf, nbytes, ppos);
}
static unsigned int
@@ -2142,7 +2151,7 @@ SYSCALL_DEFINE3(getrandom, char __user *, buf, size_t, count,
if (unlikely(ret))
return ret;
}
return urandom_read(NULL, buf, count, NULL);
return urandom_read_nowarn(NULL, buf, count, NULL);
}
/********************************************************************