From 005e7ac06d2b5e2994794efd700f5866beda4e54 Mon Sep 17 00:00:00 2001 From: "Tobin C. Harding" Date: Fri, 22 Jun 2018 09:15:32 +1000 Subject: [PATCH] random: Return nbytes filled from hw RNG commit 753d433b586d1d43c487e3d660f5778c7c8d58ea upstream. Currently the function get_random_bytes_arch() has return value 'void'. If the hw RNG fails we currently fall back to using get_random_bytes(). This defeats the purpose of requesting random material from the hw RNG in the first place. There are currently no intree users of get_random_bytes_arch(). Only get random bytes from the hw RNG, make function return the number of bytes retrieved from the hw RNG. Acked-by: Theodore Ts'o Reviewed-by: Steven Rostedt (VMware) Signed-off-by: Tobin C. Harding Signed-off-by: Theodore Ts'o Signed-off-by: Jason A. Donenfeld Signed-off-by: Greg Kroah-Hartman --- drivers/char/random.c | 16 +++++++++------- include/linux/random.h | 2 +- 2 files changed, 10 insertions(+), 8 deletions(-) diff --git a/drivers/char/random.c b/drivers/char/random.c index 05339b61dce8..859b56d41c26 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -1730,26 +1730,28 @@ EXPORT_SYMBOL(del_random_ready_callback); * key known by the NSA). So it's useful if we need the speed, but * only if we're willing to trust the hardware manufacturer not to * have put in a back door. + * + * Return number of bytes filled in. */ -void get_random_bytes_arch(void *buf, int nbytes) +int __must_check get_random_bytes_arch(void *buf, int nbytes) { + int left = nbytes; char *p = buf; - trace_get_random_bytes_arch(nbytes, _RET_IP_); - while (nbytes) { + trace_get_random_bytes_arch(left, _RET_IP_); + while (left) { unsigned long v; - int chunk = min(nbytes, (int)sizeof(unsigned long)); + int chunk = min_t(int, left, sizeof(unsigned long)); if (!arch_get_random_long(&v)) break; memcpy(p, &v, chunk); p += chunk; - nbytes -= chunk; + left -= chunk; } - if (nbytes) - get_random_bytes(p, nbytes); + return nbytes - left; } EXPORT_SYMBOL(get_random_bytes_arch); diff --git a/include/linux/random.h b/include/linux/random.h index 1f22882b099a..0d8b343b7014 100644 --- a/include/linux/random.h +++ b/include/linux/random.h @@ -38,7 +38,7 @@ extern void get_random_bytes(void *buf, int nbytes); extern int wait_for_random_bytes(void); extern int add_random_ready_callback(struct random_ready_callback *rdy); extern void del_random_ready_callback(struct random_ready_callback *rdy); -extern void get_random_bytes_arch(void *buf, int nbytes); +extern int __must_check get_random_bytes_arch(void *buf, int nbytes); #ifndef MODULE extern const struct file_operations random_fops, urandom_fops; -- 2.20.1