linux-kernel - [PATCH 8/9] random: tighten bound on random_read_wakeup

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Message-ID: <20131113080835.GV16018@ringworld.MIT.EDU>
Date:	Wed, 13 Nov 2013 03:08:35 -0500
From:	Greg Price <price@....EDU>
To:	"Theodore Ts'o" <tytso@....edu>
Cc:	linux-kernel@...r.kernel.org
Subject: [PATCH 8/9] random: tighten bound on random_read_wakeup_thresh

We use this value in a few places other than its literal meaning,
in particular in _xfer_secondary_pool() as a minimum number of
bits to pull from the input pool at a time into either output
pool.  It doesn't make sense to pull more bits than the whole size
of an output pool.

We could and possibly should separate the quantities "how much
should the input pool have to have to wake up /dev/random readers"
and "how much should we transfer from the input to an output pool
at a time", but nobody is likely to be sad they can't set the first
quantity to more than 1024 bits, so for now just limit them both.

Cc: "Theodore Ts'o" <tytso@....edu>
Signed-off-by: Greg Price <price@....edu>
---
 drivers/char/random.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/char/random.c b/drivers/char/random.c
index 1f43f9e..865c8db 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -1494,7 +1494,7 @@ EXPORT_SYMBOL(generate_random_uuid);
 #include <linux/sysctl.h>

 static int min_read_thresh = 8, min_write_thresh;
-static int max_read_thresh = INPUT_POOL_WORDS * 32;
+static int max_read_thresh = OUTPUT_POOL_WORDS * 32;
 static int max_write_thresh = INPUT_POOL_WORDS * 32;
 static char sysctl_bootid[16];

-- 
1.8.3.2

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