From: Jason Cooper <jason@lakedaemon.net>
To: Kees Cook <keescook@chromium.org>,
Michael Ellerman <mpe@ellerman.id.au>,
"Roberts, William C" <william.c.roberts@intel.com>,
Yann Droneaud <ydroneaud@opteya.com>
Cc: Linux-MM <linux-mm@kvack.org>,
LKML <linux-kernel@vger.kernel.org>,
kernel-hardening <kernel-hardening@lists.openwall.com>,
Russell King - ARM Linux <linux@arm.linux.org.uk>,
Andrew Morton <akpm@linux-foundation.org>,
Theodore Ts'o <tytso@mit.edu>, Arnd Bergmann <arnd@arndb.de>,
gregkh@linuxfoundation.org,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will.deacon@arm.com>,
Ralf Baechle <ralf@linux-mips.org>,
benh@kernel.crashing.org, paulus@samba.org,
"David S. Miller" <davem@davemloft.net>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, "H . Peter Anvin" <hpa@zytor.com>,
x86@kernel.org, viro@zeniv.linux.org.uk,
Nick Kralevich <nnk@google.com>,
Jeffrey Vander Stoep <jeffv@google.com>,
Daniel Cashman <dcashman@android.com>,
Jason Cooper <jason@lakedaemon.net>
Subject: [kernel-hardening] [PATCH v3 1/7] random: Simplify API for random address requests
Date: Wed, 3 Aug 2016 23:39:07 +0000 [thread overview]
Message-ID: <20160803233913.32511-2-jason@lakedaemon.net> (raw)
In-Reply-To: <20160803233913.32511-1-jason@lakedaemon.net>
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 < UINT_MAX. However, we should match caller expectations
to avoid coming up short (ha!) in the future.
All current callers to randomize_range() chose to use the start address
if randomize_range() failed. Therefore, we simplify things by just
returning the start address on error.
randomize_range() will be removed once all callers have been converted
over to randomize_addr().
Signed-off-by: Jason Cooper <jason@lakedaemon.net>
---
Changes from v2:
- s/randomize_addr/randomize_page/ (Kees Cook)
- PAGE_ALIGN(start) if it wasn't (Kees Cook, Michael Ellerman)
drivers/char/random.c | 33 +++++++++++++++++++++++++++++++++
include/linux/random.h | 1 +
2 files changed, 34 insertions(+)
diff --git a/drivers/char/random.c b/drivers/char/random.c
index 0158d3bff7e5..61cb434e3bea 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -1840,6 +1840,39 @@ randomize_range(unsigned long start, unsigned long end, unsigned long len)
return PAGE_ALIGN(get_random_int() % range + start);
}
+/**
+ * randomize_page - Generate a random, page aligned address
+ * @start: The smallest acceptable address the caller will take.
+ * @range: The size of the area, starting at @start, within which the
+ * random address must fall.
+ *
+ * If @start + @range would overflow, @range is capped.
+ *
+ * NOTE: Historical use of randomize_range, which this replaces, presumed that
+ * @start was already page aligned. We now align it regardless.
+ *
+ * Return: A page aligned address within [start, start + range). On error,
+ * @start is returned.
+ */
+unsigned long
+randomize_page(unsigned long start, unsigned long range)
+{
+ if (!PAGE_ALIGNED(start)) {
+ range -= PAGE_ALIGN(start) - start;
+ start = PAGE_ALIGN(start);
+ }
+
+ if (start > ULONG_MAX - range)
+ range = ULONG_MAX - start;
+
+ range >>= PAGE_SHIFT;
+
+ if (range == 0)
+ return start;
+
+ return start + (get_random_long() % range << PAGE_SHIFT);
+}
+
/* Interface for in-kernel drivers of true hardware RNGs.
* Those devices may produce endless random bits and will be throttled
* when our pool is full.
diff --git a/include/linux/random.h b/include/linux/random.h
index e47e533742b5..098fec690d65 100644
--- a/include/linux/random.h
+++ b/include/linux/random.h
@@ -35,6 +35,7 @@ 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_page(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:[~2016-08-03 23:39 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-07-28 20:47 [kernel-hardening] [PATCH 0/7] char/random: Simplify random address requests Jason Cooper
2016-07-28 20:47 ` [kernel-hardening] [PATCH 1/7] random: Simplify API for " Jason Cooper
2016-07-29 8:59 ` [kernel-hardening] " Yann Droneaud
2016-07-29 18:20 ` Jason Cooper
2016-07-28 20:47 ` [kernel-hardening] [PATCH 2/7] x86: Use simpler " Jason Cooper
2016-07-28 20:47 ` [kernel-hardening] [PATCH 3/7] ARM: " Jason Cooper
2016-07-28 20:47 ` [kernel-hardening] [PATCH 4/7] arm64: " Jason Cooper
2016-07-29 13:48 ` [kernel-hardening] " Will Deacon
2016-07-28 20:47 ` [kernel-hardening] [PATCH 5/7] tile: " Jason Cooper
2016-07-28 20:47 ` [kernel-hardening] [PATCH 6/7] unicore32: " Jason Cooper
2016-07-28 20:47 ` [kernel-hardening] [PATCH 7/7] random: Remove unused randomize_range() Jason Cooper
2016-07-30 15:42 ` [kernel-hardening] [PATCH v2 0/7] char/random: Simplify random address requests Jason Cooper
2016-07-30 15:42 ` [kernel-hardening] [PATCH v2 1/7] random: Simplify API for " Jason Cooper
2016-07-31 16:46 ` [kernel-hardening] " Kees Cook
2016-07-31 20:56 ` Jason Cooper
2016-08-01 19:47 ` Kees Cook
2016-08-01 23:17 ` Jason Cooper
2016-08-02 3:35 ` Michael Ellerman
2016-08-03 18:42 ` Jason Cooper
2016-07-30 15:42 ` [kernel-hardening] [PATCH v2 2/7] x86: Use simpler " Jason Cooper
2016-07-30 15:42 ` [kernel-hardening] [PATCH v2 3/7] ARM: " Jason Cooper
2016-07-30 15:42 ` [kernel-hardening] [PATCH v2 4/7] arm64: " Jason Cooper
2016-07-30 15:42 ` [kernel-hardening] [PATCH v2 5/7] tile: " Jason Cooper
2016-07-30 15:42 ` [kernel-hardening] [PATCH v2 6/7] unicore32: " Jason Cooper
2016-07-30 15:42 ` [kernel-hardening] [PATCH v2 7/7] random: Remove unused randomize_range() Jason Cooper
2016-08-03 23:39 ` [kernel-hardening] [PATCH v3 0/7] char/random: Simplify random address requests Jason Cooper
2016-08-03 23:39 ` Jason Cooper [this message]
2016-08-04 12:47 ` [kernel-hardening] Re: [PATCH v3 1/7] random: Simplify API for " Yann Droneaud
2016-08-03 23:39 ` [kernel-hardening] [PATCH v3 2/7] x86: Use simpler " Jason Cooper
2016-08-03 23:39 ` [kernel-hardening] [PATCH v3 3/7] ARM: " Jason Cooper
2016-08-03 23:39 ` [kernel-hardening] [PATCH v3 4/7] arm64: " Jason Cooper
2016-08-03 23:39 ` [kernel-hardening] [PATCH v3 5/7] tile: " Jason Cooper
2016-08-03 23:39 ` [kernel-hardening] [PATCH v3 6/7] unicore32: " Jason Cooper
2016-08-03 23:39 ` [kernel-hardening] [PATCH v3 7/7] random: Remove unused randomize_range() Jason Cooper
2016-08-03 23:48 ` [kernel-hardening] " Andrew Morton
2016-08-04 0:19 ` Jason Cooper
2016-08-04 2:41 ` [kernel-hardening] Re: [PATCH v3 0/7] char/random: Simplify random address requests Kees Cook
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20160803233913.32511-2-jason@lakedaemon.net \
--to=jason@lakedaemon.net \
--cc=akpm@linux-foundation.org \
--cc=arnd@arndb.de \
--cc=benh@kernel.crashing.org \
--cc=catalin.marinas@arm.com \
--cc=davem@davemloft.net \
--cc=dcashman@android.com \
--cc=gregkh@linuxfoundation.org \
--cc=hpa@zytor.com \
--cc=jeffv@google.com \
--cc=keescook@chromium.org \
--cc=kernel-hardening@lists.openwall.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=linux@arm.linux.org.uk \
--cc=mingo@redhat.com \
--cc=mpe@ellerman.id.au \
--cc=nnk@google.com \
--cc=paulus@samba.org \
--cc=ralf@linux-mips.org \
--cc=tglx@linutronix.de \
--cc=tytso@mit.edu \
--cc=viro@zeniv.linux.org.uk \
--cc=will.deacon@arm.com \
--cc=william.c.roberts@intel.com \
--cc=x86@kernel.org \
--cc=ydroneaud@opteya.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).