Commit b8c22594 authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge branch 'locking-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull locking fixes from Ingo Molnar:
 "Two futex fixes: a input parameters robustness fix, and futex race
  fixes"

* 'locking-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  futex: Prevent overflow by strengthen input validation
  futex: Avoid violating the 10th rule of futex
parents 88dc7fca fbe0e839
......@@ -1878,6 +1878,9 @@ static int futex_requeue(u32 __user *uaddr1, unsigned int flags,
struct futex_q *this, *next;
DEFINE_WAKE_Q(wake_q);
if (nr_wake < 0 || nr_requeue < 0)
return -EINVAL;
/*
* When PI not supported: return -ENOSYS if requeue_pi is true,
* consequently the compiler knows requeue_pi is always false past
......@@ -2294,21 +2297,17 @@ static void unqueue_me_pi(struct futex_q *q)
spin_unlock(q->lock_ptr);
}
/*
* Fixup the pi_state owner with the new owner.
*
* Must be called with hash bucket lock held and mm->sem held for non
* private futexes.
*/
static int fixup_pi_state_owner(u32 __user *uaddr, struct futex_q *q,
struct task_struct *newowner)
struct task_struct *argowner)
{
u32 newtid = task_pid_vnr(newowner) | FUTEX_WAITERS;
struct futex_pi_state *pi_state = q->pi_state;
u32 uval, uninitialized_var(curval), newval;
struct task_struct *oldowner;
struct task_struct *oldowner, *newowner;
u32 newtid;
int ret;
lockdep_assert_held(q->lock_ptr);
raw_spin_lock_irq(&pi_state->pi_mutex.wait_lock);
oldowner = pi_state->owner;
......@@ -2317,11 +2316,17 @@ static int fixup_pi_state_owner(u32 __user *uaddr, struct futex_q *q,
newtid |= FUTEX_OWNER_DIED;
/*
* We are here either because we stole the rtmutex from the
* previous highest priority waiter or we are the highest priority
* waiter but have failed to get the rtmutex the first time.
* We are here because either:
*
* - we stole the lock and pi_state->owner needs updating to reflect
* that (@argowner == current),
*
* or:
*
* - someone stole our lock and we need to fix things to point to the
* new owner (@argowner == NULL).
*
* We have to replace the newowner TID in the user space variable.
* Either way, we have to replace the TID in the user space variable.
* This must be atomic as we have to preserve the owner died bit here.
*
* Note: We write the user space value _before_ changing the pi_state
......@@ -2334,6 +2339,42 @@ static int fixup_pi_state_owner(u32 __user *uaddr, struct futex_q *q,
* in the PID check in lookup_pi_state.
*/
retry:
if (!argowner) {
if (oldowner != current) {
/*
* We raced against a concurrent self; things are
* already fixed up. Nothing to do.
*/
ret = 0;
goto out_unlock;
}
if (__rt_mutex_futex_trylock(&pi_state->pi_mutex)) {
/* We got the lock after all, nothing to fix. */
ret = 0;
goto out_unlock;
}
/*
* Since we just failed the trylock; there must be an owner.
*/
newowner = rt_mutex_owner(&pi_state->pi_mutex);
BUG_ON(!newowner);
} else {
WARN_ON_ONCE(argowner != current);
if (oldowner == current) {
/*
* We raced against a concurrent self; things are
* already fixed up. Nothing to do.
*/
ret = 0;
goto out_unlock;
}
newowner = argowner;
}
newtid = task_pid_vnr(newowner) | FUTEX_WAITERS;
if (get_futex_value_locked(&uval, uaddr))
goto handle_fault;
......@@ -2434,15 +2475,28 @@ static int fixup_owner(u32 __user *uaddr, struct futex_q *q, int locked)
* Got the lock. We might not be the anticipated owner if we
* did a lock-steal - fix up the PI-state in that case:
*
* We can safely read pi_state->owner without holding wait_lock
* because we now own the rt_mutex, only the owner will attempt
* to change it.
* Speculative pi_state->owner read (we don't hold wait_lock);
* since we own the lock pi_state->owner == current is the
* stable state, anything else needs more attention.
*/
if (q->pi_state->owner != current)
ret = fixup_pi_state_owner(uaddr, q, current);
goto out;
}
/*
* If we didn't get the lock; check if anybody stole it from us. In
* that case, we need to fix up the uval to point to them instead of
* us, otherwise bad things happen. [10]
*
* Another speculative read; pi_state->owner == current is unstable
* but needs our attention.
*/
if (q->pi_state->owner == current) {
ret = fixup_pi_state_owner(uaddr, q, NULL);
goto out;
}
/*
* Paranoia check. If we did not take the lock, then we should not be
* the owner of the rt_mutex.
......
......@@ -1290,6 +1290,19 @@ rt_mutex_slowlock(struct rt_mutex *lock, int state,
return ret;
}
static inline int __rt_mutex_slowtrylock(struct rt_mutex *lock)
{
int ret = try_to_take_rt_mutex(lock, current, NULL);
/*
* try_to_take_rt_mutex() sets the lock waiters bit
* unconditionally. Clean this up.
*/
fixup_rt_mutex_waiters(lock);
return ret;
}
/*
* Slow path try-lock function:
*/
......@@ -1312,13 +1325,7 @@ static inline int rt_mutex_slowtrylock(struct rt_mutex *lock)
*/
raw_spin_lock_irqsave(&lock->wait_lock, flags);
ret = try_to_take_rt_mutex(lock, current, NULL);
/*
* try_to_take_rt_mutex() sets the lock waiters bit
* unconditionally. Clean this up.
*/
fixup_rt_mutex_waiters(lock);
ret = __rt_mutex_slowtrylock(lock);
raw_spin_unlock_irqrestore(&lock->wait_lock, flags);
......@@ -1505,6 +1512,11 @@ int __sched rt_mutex_futex_trylock(struct rt_mutex *lock)
return rt_mutex_slowtrylock(lock);
}
int __sched __rt_mutex_futex_trylock(struct rt_mutex *lock)
{
return __rt_mutex_slowtrylock(lock);
}
/**
* rt_mutex_timed_lock - lock a rt_mutex interruptible
* the timeout structure is provided
......
......@@ -148,6 +148,7 @@ extern bool rt_mutex_cleanup_proxy_lock(struct rt_mutex *lock,
struct rt_mutex_waiter *waiter);
extern int rt_mutex_futex_trylock(struct rt_mutex *l);
extern int __rt_mutex_futex_trylock(struct rt_mutex *l);
extern void rt_mutex_futex_unlock(struct rt_mutex *lock);
extern bool __rt_mutex_futex_unlock(struct rt_mutex *lock,
......
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