diff options
| author | Thomas Gleixner <tglx@linutronix.de> | 2010-02-02 11:40:27 +0100 |
|---|---|---|
| committer | Thomas Gleixner <tglx@linutronix.de> | 2010-02-03 15:13:22 +0100 |
| commit | 51246bfd189064079c54421507236fd2723b18f3 (patch) | |
| tree | 060060ee3fe1cfe7c3ab510e4aff8a9dc3a7c64f | |
| parent | 5ecb01cfdf96c5f465192bdb2a4fd4a61a24c6cc (diff) | |
futex: Handle user space corruption gracefully
If the owner of a PI futex dies we fix up the pi_state and set
pi_state->owner to NULL. When a malicious or just sloppy programmed
user space application sets the futex value to 0 e.g. by calling
pthread_mutex_init(), then the futex can be acquired again. A new
waiter manages to enqueue itself on the pi_state w/o damage, but on
unlock the kernel dereferences pi_state->owner and oopses.
Prevent this by checking pi_state->owner in the unlock path. If
pi_state->owner is not current we know that user space manipulated the
futex value. Ignore the mess and return -EINVAL.
This catches the above case and also the case where a task hijacks the
futex by setting the tid value and then tries to unlock it.
Reported-by: Jermome Marchand <jmarchan@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Darren Hart <dvhltc@us.ibm.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: <stable@kernel.org>
| -rw-r--r-- | kernel/futex.c | 7 |
1 files changed, 7 insertions, 0 deletions
diff --git a/kernel/futex.c b/kernel/futex.c index 17828033a639..06e8240d2abe 100644 --- a/kernel/futex.c +++ b/kernel/futex.c @@ -758,6 +758,13 @@ static int wake_futex_pi(u32 __user *uaddr, u32 uval, struct futex_q *this) if (!pi_state) return -EINVAL; + /* + * If current does not own the pi_state then the futex is + * inconsistent and user space fiddled with the futex value. + */ + if (pi_state->owner != current) + return -EINVAL; + raw_spin_lock(&pi_state->pi_mutex.wait_lock); new_owner = rt_mutex_next_owner(&pi_state->pi_mutex); |