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futex: Split out the waiter check from lookup_pi_state()

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We want to be a bit more clever in futex_lock_pi_atomic() and separate
the possible states. Split out the waiter verification into a separate
function. No functional change.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Darren Hart <darren@dvhart.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Davidlohr Bueso <davidlohr@hp.com>
Cc: Kees Cook <kees@outflux.net>
Cc: wad@chromium.org
Link: http://lkml.kernel.org/r/20140611204237.180458410@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
This commit is contained in:
Thomas Gleixner 2014-06-11 20:45:39 +00:00
parent bd1dbcc67c
commit e60cbc5cea
1 changed files with 79 additions and 75 deletions
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154
kernel/futex.c
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@ -792,6 +792,79 @@ void exit_pi_state_list(struct task_struct *curr)
* [10] There is no transient state which leaves owner and user space
* TID out of sync.
*/
/*
* Validate that the existing waiter has a pi_state and sanity check
* the pi_state against the user space value. If correct, attach to
* it.
*/
static int attach_to_pi_state(u32 uval, struct futex_pi_state *pi_state,
struct futex_pi_state **ps)
{
pid_t pid = uval & FUTEX_TID_MASK;
/*
* Userspace might have messed up non-PI and PI futexes [3]
*/
if (unlikely(!pi_state))
return -EINVAL;
WARN_ON(!atomic_read(&pi_state->refcount));
/*
* Handle the owner died case:
*/
if (uval & FUTEX_OWNER_DIED) {
/*
* exit_pi_state_list sets owner to NULL and wakes the
* topmost waiter. The task which acquires the
* pi_state->rt_mutex will fixup owner.
*/
if (!pi_state->owner) {
/*
* No pi state owner, but the user space TID
* is not 0. Inconsistent state. [5]
*/
if (pid)
return -EINVAL;
/*
* Take a ref on the state and return success. [4]
*/
goto out_state;
}
/*
* If TID is 0, then either the dying owner has not
* yet executed exit_pi_state_list() or some waiter
* acquired the rtmutex in the pi state, but did not
* yet fixup the TID in user space.
*
* Take a ref on the state and return success. [6]
*/
if (!pid)
goto out_state;
} else {
/*
* If the owner died bit is not set, then the pi_state
* must have an owner. [7]
*/
if (!pi_state->owner)
return -EINVAL;
}
/*
* Bail out if user space manipulated the futex value. If pi
* state exists then the owner TID must be the same as the
* user space TID. [9/10]
*/
if (pid != task_pid_vnr(pi_state->owner))
return -EINVAL;
out_state:
atomic_inc(&pi_state->refcount);
*ps = pi_state;
return 0;
}
static int
lookup_pi_state(u32 uval, struct futex_hash_bucket *hb,
union futex_key *key, struct futex_pi_state **ps)
@ -801,81 +874,12 @@ lookup_pi_state(u32 uval, struct futex_hash_bucket *hb,
struct task_struct *p;
pid_t pid = uval & FUTEX_TID_MASK;
if (match) {
/*
* Sanity check the waiter before increasing the
* refcount and attaching to it.
*/
pi_state = match->pi_state;
/*
* Userspace might have messed up non-PI and PI
* futexes [3]
*/
if (unlikely(!pi_state))
return -EINVAL;
WARN_ON(!atomic_read(&pi_state->refcount));
/*
* Handle the owner died case:
*/
if (uval & FUTEX_OWNER_DIED) {
/*
* exit_pi_state_list sets owner to NULL and
* wakes the topmost waiter. The task which
* acquires the pi_state->rt_mutex will fixup
* owner.
*/
if (!pi_state->owner) {
/*
* No pi state owner, but the user
* space TID is not 0. Inconsistent
* state. [5]
*/
if (pid)
return -EINVAL;
/*
* Take a ref on the state and
* return. [4]
*/
goto out_state;
}
/*
* If TID is 0, then either the dying owner
* has not yet executed exit_pi_state_list()
* or some waiter acquired the rtmutex in the
* pi state, but did not yet fixup the TID in
* user space.
*
* Take a ref on the state and return. [6]
*/
if (!pid)
goto out_state;
} else {
/*
* If the owner died bit is not set,
* then the pi_state must have an
* owner. [7]
*/
if (!pi_state->owner)
return -EINVAL;
}
/*
* Bail out if user space manipulated the
* futex value. If pi state exists then the
* owner TID must be the same as the user
* space TID. [9/10]
*/
if (pid != task_pid_vnr(pi_state->owner))
return -EINVAL;
out_state:
atomic_inc(&pi_state->refcount);
*ps = pi_state;
return 0;
}
/*
* If there is a waiter on that futex, validate it and
* attach to the pi_state when the validation succeeds.
*/
if (match)
return attach_to_pi_state(uval, match->pi_state, ps);
/*
* We are the first waiter - try to look up the real owner and attach