From: "Jason A. Donenfeld" Jason@zx2c4.com
commit a6adf8e7a605250b911e94793fd077933709ff9e upstream.
This pulls all of the userspace read/write-focused functions into the fifth labeled section.
No functional changes.
Cc: Theodore Ts'o tytso@mit.edu Reviewed-by: Eric Biggers ebiggers@google.com Reviewed-by: Dominik Brodowski linux@dominikbrodowski.net Signed-off-by: Jason A. Donenfeld Jason@zx2c4.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/char/random.c | 125 ++++++++++++++++++++++++++++++-------------------- 1 file changed, 77 insertions(+), 48 deletions(-)
--- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -1472,30 +1472,61 @@ static void try_to_generate_entropy(void mix_pool_bytes(&stack.now, sizeof(stack.now)); }
-static ssize_t urandom_read(struct file *file, char __user *buf, size_t nbytes, - loff_t *ppos) + +/********************************************************************** + * + * Userspace reader/writer interfaces. + * + * getrandom(2) is the primary modern interface into the RNG and should + * be used in preference to anything else. + * + * Reading from /dev/random has the same functionality as calling + * getrandom(2) with flags=0. In earlier versions, however, it had + * vastly different semantics and should therefore be avoided, to + * prevent backwards compatibility issues. + * + * Reading from /dev/urandom has the same functionality as calling + * getrandom(2) with flags=GRND_INSECURE. Because it does not block + * waiting for the RNG to be ready, it should not be used. + * + * Writing to either /dev/random or /dev/urandom adds entropy to + * the input pool but does not credit it. + * + * Polling on /dev/random indicates when the RNG is initialized, on + * the read side, and when it wants new entropy, on the write side. + * + * Both /dev/random and /dev/urandom have the same set of ioctls for + * adding entropy, getting the entropy count, zeroing the count, and + * reseeding the crng. + * + **********************************************************************/ + +SYSCALL_DEFINE3(getrandom, char __user *, buf, size_t, count, unsigned int, + flags) { - static int maxwarn = 10; + if (flags & ~(GRND_NONBLOCK | GRND_RANDOM | GRND_INSECURE)) + return -EINVAL;
- if (!crng_ready() && maxwarn > 0) { - maxwarn--; - if (__ratelimit(&urandom_warning)) - pr_notice("%s: uninitialized urandom read (%zd bytes read)\n", - current->comm, nbytes); - } + /* + * Requesting insecure and blocking randomness at the same time makes + * no sense. + */ + if ((flags & (GRND_INSECURE | GRND_RANDOM)) == (GRND_INSECURE | GRND_RANDOM)) + return -EINVAL;
- return get_random_bytes_user(buf, nbytes); -} + if (count > INT_MAX) + count = INT_MAX;
-static ssize_t random_read(struct file *file, char __user *buf, size_t nbytes, - loff_t *ppos) -{ - int ret; + if (!(flags & GRND_INSECURE) && !crng_ready()) { + int ret;
- ret = wait_for_random_bytes(); - if (ret != 0) - return ret; - return get_random_bytes_user(buf, nbytes); + if (flags & GRND_NONBLOCK) + return -EAGAIN; + ret = wait_for_random_bytes(); + if (unlikely(ret)) + return ret; + } + return get_random_bytes_user(buf, count); }
static __poll_t random_poll(struct file *file, poll_table *wait) @@ -1547,6 +1578,32 @@ static ssize_t random_write(struct file return (ssize_t)count; }
+static ssize_t urandom_read(struct file *file, char __user *buf, size_t nbytes, + loff_t *ppos) +{ + static int maxwarn = 10; + + if (!crng_ready() && maxwarn > 0) { + maxwarn--; + if (__ratelimit(&urandom_warning)) + pr_notice("%s: uninitialized urandom read (%zd bytes read)\n", + current->comm, nbytes); + } + + return get_random_bytes_user(buf, nbytes); +} + +static ssize_t random_read(struct file *file, char __user *buf, size_t nbytes, + loff_t *ppos) +{ + int ret; + + ret = wait_for_random_bytes(); + if (ret != 0) + return ret; + return get_random_bytes_user(buf, nbytes); +} + static long random_ioctl(struct file *f, unsigned int cmd, unsigned long arg) { int size, ent_count; @@ -1555,7 +1612,7 @@ static long random_ioctl(struct file *f,
switch (cmd) { case RNDGETENTCNT: - /* inherently racy, no point locking */ + /* Inherently racy, no point locking. */ if (put_user(input_pool.entropy_count, p)) return -EFAULT; return 0; @@ -1631,34 +1688,6 @@ const struct file_operations urandom_fop .llseek = noop_llseek, };
-SYSCALL_DEFINE3(getrandom, char __user *, buf, size_t, count, unsigned int, - flags) -{ - if (flags & ~(GRND_NONBLOCK | GRND_RANDOM | GRND_INSECURE)) - return -EINVAL; - - /* - * Requesting insecure and blocking randomness at the same time makes - * no sense. - */ - if ((flags & (GRND_INSECURE | GRND_RANDOM)) == (GRND_INSECURE | GRND_RANDOM)) - return -EINVAL; - - if (count > INT_MAX) - count = INT_MAX; - - if (!(flags & GRND_INSECURE) && !crng_ready()) { - int ret; - - if (flags & GRND_NONBLOCK) - return -EAGAIN; - ret = wait_for_random_bytes(); - if (unlikely(ret)) - return ret; - } - return get_random_bytes_user(buf, count); -} - /******************************************************************** * * Sysctl interface