linux-kernel - [PATCH 4.9 027/264] random: always fill buffer in get_random_bytes

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Date:   Thu, 23 Jun 2022 18:40:20 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, "Jason A. Donenfeld" <Jason@...c4.com>,
        Theodore Tso <tytso@....edu>
Subject: [PATCH 4.9 027/264] random: always fill buffer in get_random_bytes_wait

From: "Jason A. Donenfeld" <Jason@...c4.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@...c4.com>
Signed-off-by: Theodore Ts'o <tytso@....edu>
Signed-off-by: Jason A. Donenfeld <Jason@...c4.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.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) \