linux-kernel - [PATCH] random: always fill buffer in get_random_bytes

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Message-Id: <20180204220746.12441-1-Jason@zx2c4.com>
Date:   Sun,  4 Feb 2018 23:07:46 +0100
From:   "Jason A. Donenfeld" <Jason@...c4.com>
To:     tytso@....edu, gregkh@...uxfoundation.org,
        linux-kernel@...r.kernel.org
Cc:     "Jason A. Donenfeld" <Jason@...c4.com>
Subject: [PATCH] random: always fill buffer in get_random_bytes_wait

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@...c4.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