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random: Return nbytes filled from hw RNG

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commit 753d433b58 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 <tytso@mit.edu>
Reviewed-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Tobin C. Harding <me@tobin.cc>
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:
Tobin C. Harding
2018-06-22 09:15:32 +10:00
committed by Chris
parent cfa71da226
commit b64d189a46
2 changed files with 10 additions and 8 deletions
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16
drivers/char/random.c
View File

@@ -1731,26 +1731,28 @@ 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);

2
include/linux/random.h
View File

@@ -37,7 +37,7 @@ 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;