From: Thomas Gleixner <tglx@linutronix.de>
To: LKML <linux-kernel@vger.kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>,
Darren Hart <darren@dvhart.com>, Ingo Molnar <mingo@kernel.org>,
Davidlohr Bueso <davidlohr@hp.com>, Kees Cook <kees@outflux.net>,
wad@chromium.org
Subject: [patch 0/5] futex: More robustness tweaks
Date: Wed, 11 Jun 2014 20:45:37 -0000 [thread overview]
Message-ID: <20140611202744.676528190@linutronix.de> (raw)
While looking for the minimal functional fix for the futex CVE, I
found a few things which can be done simpler and therefor make the
code more robust.
1) UNLOCK_PI
Change the ordering:
- Lookup waiters first. If waiters exist wake up the top priority
waiter with all sanity checks applied. That allows us to catch
manipulation of the user space value.
- Only if there are no waiters, do the atomic release
2) futex_lock_pi_atomic()
Its a maze of retry hoops and loops. Reduce it to simple and
userstandable states.
That requires to split out the lookup and validation functions from
lookup_pi_state(), but that turns out to be an overall win on
readabilty.
The overall cleanup results in less code and 488 bytes text size
reduction on x8664.
Thanks,
tglx
---
futex.c | 385 ++++++++++++++++++++++++++++------------------------------------
1 file changed, 171 insertions(+), 214 deletions(-)
next reply other threads:[~2014-06-11 20:46 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-06-11 20:45 Thomas Gleixner [this message]
2014-06-11 20:45 ` [patch 1/5] futex: Make unlock_pi more robust Thomas Gleixner
2014-06-16 16:18 ` Darren Hart
2014-06-16 22:15 ` Thomas Gleixner
2014-06-16 22:28 ` Thomas Gleixner
2014-06-16 22:49 ` Darren Hart
2014-06-16 22:39 ` Darren Hart
2014-06-21 20:33 ` [tip:locking/core] " tip-bot for Thomas Gleixner
2014-06-11 20:45 ` [patch 3/5] futex: Split out the waiter check from lookup_pi_state() Thomas Gleixner
2014-06-16 18:12 ` Darren Hart
2014-06-21 20:33 ` [tip:locking/core] " tip-bot for Thomas Gleixner
2014-06-11 20:45 ` [patch 2/5] futex: Use futex_top_waiter() in lookup_pi_state() Thomas Gleixner
2014-06-16 16:51 ` Darren Hart
2014-06-21 20:33 ` [tip:locking/core] " tip-bot for Thomas Gleixner
2014-06-11 20:45 ` [patch 4/5] futex: Split out the first waiter attachment from lookup_pi_state() Thomas Gleixner
2014-06-16 18:19 ` Darren Hart
2014-06-21 20:33 ` [tip:locking/core] " tip-bot for Thomas Gleixner
2014-06-11 20:45 ` [patch 5/5] futex: Simplify futex_lock_pi_atomic() and make it more robust Thomas Gleixner
2014-06-13 5:46 ` Darren Hart
2014-06-13 8:34 ` Thomas Gleixner
2014-06-13 9:36 ` Thomas Gleixner
2014-06-13 9:44 ` [patch V2 " Thomas Gleixner
2014-06-13 20:51 ` Davidlohr Bueso
2014-06-16 20:36 ` Darren Hart
2014-06-17 7:20 ` Thomas Gleixner
2014-06-21 20:34 ` [tip:locking/core] " tip-bot for Thomas Gleixner
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