[PATCH 4.9 027/264] random: always fill buffer in get_random_bytes_wait

Greg Kroah-Hartman
2022-06-23T16:47:45Z

From: "Jason A. Donenfeld" <Jason@zx2c4.com>

commit 25e3fca492035a2e1d4ac6e3b1edd9c1acd48897 upstream.

In the unfortunate event that a developer fails to check the return
value of get_random_bytes_wait, or simply wants to make a "best effort"
attempt, for whatever that's worth, it's much better to still fill the
buffer with _something_ rather than catastrophically failing in the case
of an interruption. This is both a defense in depth measure against
inevitable programming bugs, as well as a means of making the API a bit
more useful.

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
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>
---
include/linux/random.h | 4 +---
1 file changed, 1 insertion(+), 3 deletions(-)

--- a/include/linux/random.h
+++ b/include/linux/random.h
@@ -63,10 +63,8 @@ static inline unsigned long get_random_l
static inline int get_random_bytes_wait(void *buf, int nbytes)
{
int ret = wait_for_random_bytes();
- if (unlikely(ret))
- return ret;
get_random_bytes(buf, nbytes);
- return 0;
+ return ret;
}

#define declare_get_random_var_wait(var) \