[<prev] [next>] [thread-next>] [day] [month] [year] [list]
Message-Id: <20160726030201.6775-1-jason@lakedaemon.net>
Date: Tue, 26 Jul 2016 03:01:55 +0000
From: Jason Cooper <jason@...edaemon.net>
To: william.c.roberts@...el.com,
linux-mm@...r.kernel.org,
linux-kernel@...r.kernel.org,
kernel-hardening@...ts.openwall.com
Cc: Jason Cooper <jason@...edaemon.net>,
linux@....linux.org.uk,
akpm@...ux-foundation.org,
keescook@...omium.org,
tytso@....edu,
arnd@...db.de,
gregkh@...uxfoundation.org,
catalin.marinas@....com,
will.deacon@....com,
ralf@...ux-mips.org,
benh@...nel.crashing.org,
paulus@...ba.org,
mpe@...erman.id.au,
davem@...emloft.net,
tglx@...utronix.de,
mingo@...hat.com,
hpa@...or.com,
x86@...nel.org,
viro@...iv.linux.org.uk,
nnk@...gle.com,
jeffv@...gle.com,
alyzyn@...roid.com,
dcashman@...roid.com
Subject: [RFC patch 1/6] random: Simplify API for random address requests
To date, all callers of randomize_range() have set the length to 0, and
check for a zero return value. For the current callers, the only way
to get zero returned is if end <= start. Since they are all adding a
constant to the start address, this is unnecessary.
We can remove a bunch of needless checks by simplifying the API to do
just what everyone wants, return an address between [start, start +
range].
While we're here, s/get_random_int/get_random_long/. No current call
site is adversely affected by get_random_int(), since all current range
requests are < MAX_UINT. However, we should match caller expectations
to avoid coming up short (ha!) in the future.
Signed-off-by: Jason Cooper <jason@...edaemon.net>
---
drivers/char/random.c | 17 ++++-------------
include/linux/random.h | 2 +-
2 files changed, 5 insertions(+), 14 deletions(-)
diff --git a/drivers/char/random.c b/drivers/char/random.c
index 0158d3bff7e5..1251cb2cbab2 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -1822,22 +1822,13 @@ unsigned long get_random_long(void)
EXPORT_SYMBOL(get_random_long);
/*
- * randomize_range() returns a start address such that
- *
- * [...... <range> .....]
- * start end
- *
- * a <range> with size "len" starting at the return value is inside in the
- * area defined by [start, end], but is otherwise randomized.
+ * randomize_addr() returns a page aligned address within [start, start +
+ * range]
*/
unsigned long
-randomize_range(unsigned long start, unsigned long end, unsigned long len)
+randomize_addr(unsigned long start, unsigned long range)
{
- unsigned long range = end - len - start;
-
- if (end <= start + len)
- return 0;
- return PAGE_ALIGN(get_random_int() % range + start);
+ return PAGE_ALIGN(get_random_long() % range + start);
}
/* Interface for in-kernel drivers of true hardware RNGs.
diff --git a/include/linux/random.h b/include/linux/random.h
index e47e533742b5..1ad877a98186 100644
--- a/include/linux/random.h
+++ b/include/linux/random.h
@@ -34,7 +34,7 @@ extern const struct file_operations random_fops, urandom_fops;
unsigned int get_random_int(void);
unsigned long get_random_long(void);
-unsigned long randomize_range(unsigned long start, unsigned long end, unsigned long len);
+unsigned long randomize_addr(unsigned long start, unsigned long range);
u32 prandom_u32(void);
void prandom_bytes(void *buf, size_t nbytes);
--
2.9.2
Powered by blists - more mailing lists
Confused about mailing lists and their use?
Read about mailing lists on Wikipedia
and check out these
guidelines on proper formatting of your messages.
