From: Jason Cooper <jason@lakedaemon.net>
To: william.c.roberts@intel.com, linux-mm@vger.kernel.org,
linux-kernel@vger.kernel.org,
kernel-hardening@lists.openwall.com
Cc: Jason Cooper <jason@lakedaemon.net>,
linux@arm.linux.org.uk, akpm@linux-foundation.org,
keescook@chromium.org, tytso@mit.edu, arnd@arndb.de,
gregkh@linuxfoundation.org, catalin.marinas@arm.com,
will.deacon@arm.com, ralf@linux-mips.org,
benh@kernel.crashing.org, paulus@samba.org, mpe@ellerman.id.au,
davem@davemloft.net, tglx@linutronix.de, mingo@redhat.com,
hpa@zytor.com, x86@kernel.org, viro@zeniv.linux.org.uk,
nnk@google.com, jeffv@google.com, alyzyn@android.com,
dcashman@android.com
Subject: [RFC patch 1/6] random: Simplify API for random address requests
Date: Tue, 26 Jul 2016 03:01:55 +0000 [thread overview]
Message-ID: <20160726030201.6775-1-jason@lakedaemon.net> (raw)
In-Reply-To: <1469471141-25669-1-git-send-email-william.c.roberts@intel.com>
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@lakedaemon.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
next prev parent reply other threads:[~2016-07-26 3:05 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-07-25 18:25 [PATCH] randomize_range: use random long instead of int william.c.roberts
2016-07-25 18:54 ` Kees Cook
2016-07-26 2:18 ` Jason Cooper
2016-07-26 3:01 ` Jason Cooper [this message]
2016-07-26 3:01 ` [RFC patch 2/6] x86: Use simpler API for random address requests Jason Cooper
2016-07-26 3:01 ` [RFC patch 3/6] ARM: " Jason Cooper
2016-07-26 3:01 ` [RFC patch 4/6] arm64: " Jason Cooper
2016-07-26 3:01 ` [RFC patch 5/6] tile: " Jason Cooper
2016-07-26 3:02 ` [RFC patch 6/6] unicore32: " Jason Cooper
2016-07-26 3:30 ` [RFC patch 1/6] random: Simplify " Jason Cooper
2016-07-26 4:39 ` Kees Cook
2016-07-26 17:00 ` Jason Cooper
2016-07-26 17:07 ` Kees Cook
2016-07-28 19:02 ` Jason Cooper
2016-07-26 17:33 ` Roberts, William C
2016-07-26 4:44 ` Kees Cook
2016-07-26 15:55 ` Jason Cooper
2016-07-26 16:40 ` Kees Cook
2016-07-27 13:51 ` [kernel-hardening] " Yann Droneaud
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