[PATCH 01/14] random: fix signedness bug

[Greg Price]

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@xxxxxxx>
---
 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

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