From: "Tobin C. Harding" me@tobin.cc
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 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 --- drivers/char/random.c | 16 +++++++++------- include/linux/random.h | 2 +- 2 files changed, 10 insertions(+), 8 deletions(-)
--- 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);
--- a/include/linux/random.h +++ b/include/linux/random.h @@ -38,7 +38,7 @@ extern void get_random_bytes(void *buf, 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;