[PATCH] random: always fill buffer in get_random_bytes_wait

[PATCH] random: always fill buffer in get_random_bytes_wait

[Jason A. Donenfeld]

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>
---
 include/linux/random.h | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/include/linux/random.h b/include/linux/random.h
index 4024f7d9c77d..2ddf13b4281e 100644
--- a/include/linux/random.h
+++ b/include/linux/random.h
@@ -85,10 +85,8 @@ static inline unsigned long get_random_canary(void)
 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) \
-- 
2.16.1

Re: [PATCH] random: always fill buffer in get_random_bytes_wait

[Jason A. Donenfeld]

Hi Ted,

Can you apply this?

Thanks,
Jason

Re: [PATCH] random: always fill buffer in get_random_bytes_wait

[Theodore Ts'o]

On Sun, Feb 04, 2018 at 11:07:46PM +0100, Jason A. Donenfeld wrote:
> 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>

Thanks, applied.

					- Ted