kernel_samsung_crespo/kernel/futex.c, branch replicant-4.2

futex: Make lookup_pi_state more robust

2014-07-17T14:50:07+00:00

The current implementation of lookup_pi_state has ambigous handling of
the TID value 0 in the user space futex. We can get into the kernel
even if the TID value is 0, because either there is a stale waiters
bit or the owner died bit is set or we are called from the requeue_pi
path or from user space just for fun.

The current code avoids an explicit sanity check for pid = 0 in case
that kernel internal state (waiters) are found for the user space
address. This can lead to state leakage and worse under some
circumstances.

Handle the cases explicit:

     Waiter | pi_state | pi->owner | uTID      | uODIED | ?

[1]  NULL   | ---      | ---       | 0         | 0/1    | Valid
[2]  NULL   | ---      | ---       | >0        | 0/1    | Valid

[3]  Found  | NULL     | --        | Any       | 0/1    | Invalid

[4]  Found  | Found    | NULL      | 0         | 1      | Valid
[5]  Found  | Found    | NULL      | >0        | 1      | Invalid

[6]  Found  | Found    | task      | 0         | 1      | Valid

[7]  Found  | Found    | NULL      | Any       | 0      | Invalid

[8]  Found  | Found    | task      | ==taskTID | 0/1    | Valid
[9]  Found  | Found    | task      | 0         | 0      | Invalid
[10] Found  | Found    | task      | !=taskTID | 0/1    | Invalid

[1]  Indicates that the kernel can acquire the futex atomically. We
     came came here due to a stale FUTEX_WAITERS/FUTEX_OWNER_DIED bit.

[2]  Valid, if TID does not belong to a kernel thread. If no matching
     thread is found then it indicates that the owner TID has died.

[3]  Invalid. The waiter is queued on a non PI futex

[4]  Valid state after exit_robust_list(), which sets the user space
     value to FUTEX_WAITERS | FUTEX_OWNER_DIED.

[5]  The user space value got manipulated between exit_robust_list()
     and exit_pi_state_list()

[6]  Valid state after exit_pi_state_list() which sets the new owner in
     the pi_state but cannot access the user space value.

[7]  pi_state->owner can only be NULL when the OWNER_DIED bit is set.

[8]  Owner and user space value match

[9]  There is no transient state which sets the user space TID to 0
     except exit_robust_list(), but this is indicated by the
     FUTEX_OWNER_DIED bit. See [4]

[10] There is no transient state which leaves owner and user space
     TID out of sync.

Backport to 3.13
  conflicts: kernel/futex.c

Change-Id: Ic410036b38ccb7289b3d58eff56ad64d3a9dcada
Signed-off-by: Thomas Gleixner 
Signed-off-by: John Johansen 
Cc: Kees Cook 
Cc: Will Drewry 
Cc: Darren Hart 
Cc: stable@vger.kernel.org

futex: Always cleanup owner tid in unlock_pi

2014-07-17T14:50:06+00:00

If the owner died bit is set at futex_unlock_pi, we currently do not
cleanup the user space futex. So the owner TID of the current owner
(the unlocker) persists. That's observable inconsistant state,
especially when the ownership of the pi state got transferred.

Clean it up unconditionally.

Change-Id: I4eeb2e139b720f1dd46e43407a96b3d9a19aacd1
Signed-off-by: Thomas Gleixner 
Cc: Kees Cook 
Cc: Will Drewry 
Cc: Darren Hart 
Cc: stable@vger.kernel.org

futex: Validate atomic acquisition in futex_lock_pi_atomic()

2014-07-17T14:50:06+00:00

We need to protect the atomic acquisition in the kernel against rogue
user space which sets the user space futex to 0, so the kernel side
acquisition succeeds while there is existing state in the kernel
associated to the real owner.

Verify whether the futex has waiters associated with kernel state. If
it has, return -EINVAL. The state is corrupted already, so no point in
cleaning it up. Subsequent calls will fail as well. Not our problem.

[ tglx: Use futex_top_waiter() and explain why we do not need to try
  	restoring the already corrupted user space state. ]

Change-Id: Ic8714ed2e9dee323a011eed42f7c0159c65dfbf3
Signed-off-by: Darren Hart 
Cc: Kees Cook 
Cc: Will Drewry 
Cc: stable@vger.kernel.org
Signed-off-by: Thomas Gleixner

futex-prevent-requeue-pi-on-same-futex.patch futex: Forbid uaddr == uaddr2 in futex_requeue(..., requeue_pi=1)

2014-07-17T14:50:06+00:00

If uaddr == uaddr2, then we have broken the rule of only requeueing
from a non-pi futex to a pi futex with this call. If we attempt this,
then dangling pointers may be left for rt_waiter resulting in an
exploitable condition.

This change brings futex_requeue() into line with
futex_wait_requeue_pi() which performs the same check as per commit
6f7b0a2a5 (futex: Forbid uaddr == uaddr2 in futex_wait_requeue_pi())

[ tglx: Compare the resulting keys as well, as uaddrs might be
  	different depending on the mapping ]

Fixes CVE-2014-3153.

Change-Id: I473bf486ad451de0bfd049a110b69795a6fda451
Reported-by: Pinkie Pie
Signed-off-by: Will Drewry 
Signed-off-by: Kees Cook 
Cc: stable@vger.kernel.org
Signed-off-by: Thomas Gleixner

futex: Add another early deadlock detection check

2014-07-17T14:50:06+00:00

Dave Jones trinity syscall fuzzer exposed an issue in the deadlock
detection code of rtmutex:
  http://lkml.kernel.org/r/20140429151655.GA14277@redhat.com

That underlying issue has been fixed with a patch to the rtmutex code,
but the futex code must not call into rtmutex in that case because
    - it can detect that issue early
    - it avoids a different and more complex fixup for backing out

If the user space variable got manipulated to 0x80000000 which means
no lock holder, but the waiters bit set and an active pi_state in the
kernel is found we can figure out the recursive locking issue by
looking at the pi_state owner. If that is the current task, then we
can safely return -EDEADLK.

The check should have been added in commit 59fa62451 (futex: Handle
futex_pi OWNER_DIED take over correctly) already, but I did not see
the above issue caused by user space manipulation back then.

Change-Id: I5242efcdc3c08159c652fe645e1f85b27687e6ca
Signed-off-by: Thomas Gleixner 
Cc: Dave Jones 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Darren Hart 
Cc: Davidlohr Bueso 
Cc: Steven Rostedt 
Cc: Clark Williams 
Cc: Paul McKenney 
Cc: Lai Jiangshan 
Cc: Roland McGrath 
Cc: Carlos ODonell 
Cc: Jakub Jelinek 
Cc: Michael Kerrisk 
Cc: Sebastian Andrzej Siewior 
Link: http://lkml.kernel.org/r/20140512201701.097349971@linutronix.de
Signed-off-by: Thomas Gleixner 
Cc: stable@vger.kernel.org

futex: Prevent attaching to kernel threads

2014-07-17T14:50:06+00:00

We happily allow userspace to declare a random kernel thread to be the
owner of a user space PI futex.

Found while analysing the fallout of Dave Jones syscall fuzzer.

We also should validate the thread group for private futexes and find
some fast way to validate whether the "alleged" owner has RW access on
the file which backs the SHM, but that's a separate issue.

Change-Id: I03941dc5737bcb9d3ddd2ec88f7c263c27a1247d
Signed-off-by: Thomas Gleixner 
Cc: Dave Jones 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Darren Hart 
Cc: Davidlohr Bueso 
Cc: Steven Rostedt 
Cc: Clark Williams 
Cc: Paul McKenney 
Cc: Lai Jiangshan 
Cc: Roland McGrath 
Cc: Carlos ODonell 
Cc: Jakub Jelinek 
Cc: Michael Kerrisk 
Cc: Sebastian Andrzej Siewior 
Link: http://lkml.kernel.org/r/20140512201701.194824402@linutronix.de
Signed-off-by: Thomas Gleixner 
Cc: stable@vger.kernel.org

Merge branch 'linux-3.0.y' into HEAD

2012-08-30T19:49:20+00:00

Conflicts:
	drivers/net/tun.c

futex: Forbid uaddr == uaddr2 in futex_wait_requeue_pi()

2012-08-09T15:27:54+00:00

commit 6f7b0a2a5c0fb03be7c25bd1745baa50582348ef upstream.

If uaddr == uaddr2, then we have broken the rule of only requeueing
from a non-pi futex to a pi futex with this call. If we attempt this,
as the trinity test suite manages to do, we miss early wakeups as
q.key is equal to key2 (because they are the same uaddr). We will then
attempt to dereference the pi_mutex (which would exist had the futex_q
been properly requeued to a pi futex) and trigger a NULL pointer
dereference.

Signed-off-by: Darren Hart 
Cc: Dave Jones 
Link: http://lkml.kernel.org/r/ad82bfe7f7d130247fbe2b5b4275654807774227.1342809673.git.dvhart@linux.intel.com
Signed-off-by: Thomas Gleixner 
Signed-off-by: Greg Kroah-Hartman

futex: Fix bug in WARN_ON for NULL q.pi_state

2012-08-09T15:27:54+00:00

commit f27071cb7fe3e1d37a9dbe6c0dfc5395cd40fa43 upstream.

The WARN_ON in futex_wait_requeue_pi() for a NULL q.pi_state was testing
the address (&q.pi_state) of the pointer instead of the value
(q.pi_state) of the pointer. Correct it accordingly.

Signed-off-by: Darren Hart 
Cc: Dave Jones 
Link: http://lkml.kernel.org/r/1c85d97f6e5f79ec389a4ead3e367363c74bd09a.1342809673.git.dvhart@linux.intel.com
Signed-off-by: Thomas Gleixner 
Signed-off-by: Greg Kroah-Hartman

futex: Test for pi_mutex on fault in futex_wait_requeue_pi()

2012-08-09T15:27:54+00:00

commit b6070a8d9853eda010a549fa9a09eb8d7269b929 upstream.

If fixup_pi_state_owner() faults, pi_mutex may be NULL. Test
for pi_mutex != NULL before testing the owner against current
and possibly unlocking it.

Signed-off-by: Darren Hart 
Cc: Dave Jones 
Cc: Dan Carpenter 
Link: http://lkml.kernel.org/r/dc59890338fc413606f04e5c5b131530734dae3d.1342809673.git.dvhart@linux.intel.com
Signed-off-by: Thomas Gleixner 
Signed-off-by: Greg Kroah-Hartman