commit cdf78db4070967869e4d027c11f4dd825d8f815a upstream.

FUTEX_LOCK_PI does not require to have the FUTEX_CLOCK_REALTIME bit set
because it has been using CLOCK_REALTIME based absolute timeouts
forever. Due to that, the time namespace adjustment which is applied when
FUTEX_CLOCK_REALTIME is not set, will wrongly take place for FUTEX_LOCK_PI
and wreckage the timeout.

Exclude it from that procedure.

Fixes: c2f7d08cccf4 ("futex: Adjust absolute futex timeouts with per time namespace offset")
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20210422194704.984540159@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

commit 4fbf5d6837bf81fd7a27d771358f4ee6c4f243f8 upstream.

The FUTEX_WAIT operand has historically a relative timeout which means that
the clock id is irrelevant as relative timeouts on CLOCK_REALTIME are not
subject to wall clock changes and therefore are mapped by the kernel to
CLOCK_MONOTONIC for simplicity.

If a caller would set FUTEX_CLOCK_REALTIME for FUTEX_WAIT the timeout is
still treated relative vs. CLOCK_MONOTONIC and then the wait arms that
timeout based on CLOCK_REALTIME which is broken and obviously has never
been used or even tested.

Reject any attempt to use FUTEX_CLOCK_REALTIME with FUTEX_WAIT again.

The desired functionality can be achieved with FUTEX_WAIT_BITSET and a
FUTEX_BITSET_MATCH_ANY argument.

Fixes: 337f13046ff0 ("futex: Allow FUTEX_CLOCK_REALTIME with FUTEX_WAIT op")
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20210422194704.834797921@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Preparation for fixing get_nr_restart_syscall() on X86 for COMPAT.

Add a new helper which sets restart_block->fn and calls a dummy
arch_set_restart_data() helper.

Fixes: 609c19a385c8 ("x86/ptrace: Stop setting TS_COMPAT in ptrace code")
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20210201174641.GA17871@redhat.com

Signed-off-by: Ingo Molnar <mingo@kernel.org>

Get rid of gotos that do not contain any cleanup. These were not removed in
commit 9180bd467f9a ("futex: Remove put_futex_key()").

Signed-off-by: Jangwoong Kim <6812skiii@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20201230122953.10473-1-6812skiii@gmail.com

futex(2) says that 'utime' is a pointer to 'const'.  The implementation
doesn't use 'const'; however, it _never_ modifies the contents of utime.

- futex() either uses 'utime' as a pointer to struct or as a 'u32'.

- In case it's used as a 'u32', it makes a copy of it, and of course it is
  not dereferenced.

- In case it's used as a 'struct __kernel_timespec __user *', the pointer
  is not dereferenced inside the futex() definition, and it is only passed
  to a function: get_timespec64(), which accepts a 'const struct
  __kernel_timespec __user *'.

[ tglx: Make the same change to the compat syscall and fixup the prototypes. ]

Signed-off-by: Alejandro Colomar <alx.manpages@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20201128123945.4592-1-alx.manpages@gmail.com

fixup_pi_state_owner() tries to ensure that the state of the rtmutex,
pi_state and the user space value related to the PI futex are consistent
before returning to user space. In case that the user space value update
faults and the fault cannot be resolved by faulting the page in via
fault_in_user_writeable() the function returns with -EFAULT and leaves
the rtmutex and pi_state owner state inconsistent.

A subsequent futex_unlock_pi() operates on the inconsistent pi_state and
releases the rtmutex despite not owning it which can corrupt the RB tree of
the rtmutex and cause a subsequent kernel stack use after free.

It was suggested to loop forever in fixup_pi_state_owner() if the fault
cannot be resolved, but that results in runaway tasks which is especially
undesired when the problem happens due to a programming error and not due
to malice.

As the user space value cannot be fixed up, the proper solution is to make
the rtmutex and the pi_state consistent so both have the same owner. This
leaves the user space value out of sync. Any subsequent operation on the
futex will fail because the 10th rule of PI futexes (pi_state owner and
user space value are consistent) has been violated.

As a consequence this removes the inept attempts of 'fixing' the situation
in case that the current task owns the rtmutex when returning with an
unresolvable fault by unlocking the rtmutex which left pi_state::owner and
rtmutex::owner out of sync in a different and only slightly less dangerous
way.

Fixes: 1b7558e457ed ("futexes: fix fault handling in futex_lock_pi")
Reported-by: gzobqq@gmail.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: stable@vger.kernel.org

Too many gotos already and an upcoming fix would make it even more
unreadable.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: stable@vger.kernel.org

No point in open coding it. This way it gains the extra sanity checks.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: stable@vger.kernel.org

Nothing uses the argument. Remove it as preparation to use
pi_state_update_owner().

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: stable@vger.kernel.org