[tip:core/urgent] futex: additional (get|put)_futex_key() fixes

Darren Hart
2009-03-13T00:25:14Z

Commit-ID: 638f9d766fa5b59953f8d1870f18fbd0cca84d33
Gitweb: http://git.kernel.org/tip/638f9d766fa5b59953f8d1870f18fbd0cca84d33
Author: Darren Hart <dvhltc@us.ibm.com>
AuthorDate: Thu, 12 Mar 2009 00:55:46 -0700
Commit: Ingo Molnar <mingo@elte.hu>
CommitDate: Fri, 13 Mar 2009 01:19:00 +0100

futex: additional (get|put)_futex_key() fixes

Impact: fix races

futex_requeue and futex_lock_pi still had some bad
(get|put)_futex_key() usage. This patch adds the missing
put_futex_keys() and corrects a goto in futex_lock_pi() to avoid
a double get.

Build and boot tested on a 4 way Intel x86_64 workstation.
Passes basic pthread_mutex and PI tests out of
ltp/testcases/realtime.

Signed-off-by: Darren Hart <dvhltc@us.ibm.com>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Cc: Rusty Russell <rusty@rustcorp.com.au>
LKML-Reference: <20090312075545.9856.75152.stgit@Aeon>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

---
kernel/futex.c | 16 +++++++++++-----
1 files changed, 11 insertions(+), 5 deletions(-)

diff --git a/kernel/futex.c b/kernel/futex.c
index 438701a..a66cd2d 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -805,8 +805,10 @@ retry:

ret = get_user(dummy, uaddr2);
if (ret)
- return ret;
+ goto out_put_keys;

+ put_futex_key(fshared, &key2);
+ put_futex_key(fshared, &key1);
goto retryfull;
}

@@ -881,6 +883,9 @@ retry:
if (hb1 != hb2)
spin_unlock(&hb2->lock);

+ put_futex_key(fshared, &key2);
+ put_futex_key(fshared, &key1);
+
ret = get_user(curval, uaddr1);

if (!ret)
@@ -1458,6 +1463,7 @@ retry_locked:
* exit to complete.
*/
queue_unlock(&q, hb);
+ put_futex_key(fshared, &q.key);
cond_resched();
goto retry;

@@ -1600,13 +1606,12 @@ uaddr_faulted:

ret = get_user(uval, uaddr);
if (!ret)
- goto retry;
+ goto retry_unlocked;

- if (to)
- destroy_hrtimer_on_stack(&to->timer);
- return ret;
+ goto out_put_key;
}

+
/*
* Userspace attempted a TID -> 0 atomic transition, and failed.
* This is the in-kernel slowpath: we look up the PI state (if any),
@@ -1710,6 +1715,7 @@ pi_faulted:
}

ret = get_user(uval, uaddr);
+ put_futex_key(fshared, &key);
if (!ret)
goto retry;