From: Greg Price <price@MIT.EDU>
To: "Theodore Ts'o" <tytso@MIT.EDU>
Cc: linux-kernel@vger.kernel.org
Subject: [PATCH 01/14] random: fix signedness bug
Date: Sat, 14 Dec 2013 21:00:51 -0500 [thread overview]
Message-ID: <20131215020051.GA27191@athena.dialup.mit.edu> (raw)
In-Reply-To: <cover.1387067223.git.price@mit.edu>
Negative numbers and size_t don't mix. When the total entropy
available was less than 'reserved', we would fail to enforce any limit
at all. Fix that. We never care how negative have_bytes - reserved
is, so just flatten it to zero if negative.
This behavior entered in 987cd8c30 "random: simplify accounting code"
a few commits ago. Before that, for a long time we would compare
have_bytes - reserved (or equivalent) to ibytes or store it into ibytes,
but only inside a condition that guaranteed it wasn't negative.
Signed-off-by: Greg Price <price@mit.edu>
---
drivers/char/random.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/drivers/char/random.c b/drivers/char/random.c
index 8cc7d6515..1dd5f2634 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -977,7 +977,8 @@ retry:
ibytes = nbytes;
/* If limited, never pull more than available */
if (r->limit)
- ibytes = min_t(size_t, ibytes, have_bytes - reserved);
+ ibytes = min_t(size_t, ibytes,
+ max(0, have_bytes - reserved));
if (ibytes < min)
ibytes = 0;
entropy_count = max_t(int, 0,
--
1.8.3.2
next prev parent reply other threads:[~2013-12-15 2:00 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-12-15 2:00 [PATCH 00/14] random: rework reseeding Greg Price
2013-12-15 2:00 ` Greg Price [this message]
2013-12-15 2:00 ` [PATCH 02/14] random: fix a (harmless) overflow Greg Price
2013-12-15 2:01 ` [PATCH 03/14] random: reserve for /dev/random only once /dev/urandom seeded Greg Price
2013-12-15 2:01 ` [PATCH 04/14] random: accept small seeds early on Greg Price
2013-12-15 2:01 ` [PATCH 05/14] random: move transfer accounting into account() helper Greg Price
2013-12-15 2:01 ` [PATCH 06/14] random: separate quantity of bytes extracted and entropy to credit Greg Price
2013-12-15 2:01 ` [PATCH 07/14] random: exploit any extra entropy too when reseeding Greg Price
2013-12-15 2:01 ` [PATCH 08/14] random: rate-limit reseeding only after properly seeded Greg Price
2013-12-15 2:01 ` [PATCH 09/14] random: reserve entropy for nonblocking pool early on Greg Price
2013-12-15 2:01 ` [PATCH 10/14] random: direct all routine input via input pool Greg Price
2013-12-15 2:01 ` [PATCH 11/14] random: separate entropy since auto-push from entropy_total Greg Price
2013-12-15 2:01 ` [PATCH 12/14] random: separate minimum reseed size from minimum /dev/random read Greg Price
2013-12-15 2:01 ` [PATCH 13/14] random: count only catastrophic reseeds for initialization Greg Price
2013-12-15 2:02 ` [PATCH 14/14] random: target giant reseeds, to be conservative Greg Price
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