Commit-ID: 51246bfd189064079c54421507236fd2723b18f3 Gitweb: http://git.kernel.org/tip/51246bfd189064079c54421507236fd2723b18f3 Author: Thomas Gleixner <tglx@xxxxxxxxxxxxx> AuthorDate: Tue, 2 Feb 2010 11:40:27 +0100 Committer: Thomas Gleixner <tglx@xxxxxxxxxxxxx> CommitDate: Wed, 3 Feb 2010 15:13:22 +0100 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@xxxxxxxxxx> Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Acked-by: Darren Hart <dvhltc@xxxxxxxxxx> Acked-by: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx> Cc: <stable@xxxxxxxxxx> --- kernel/futex.c | 7 +++++++ 1 files changed, 7 insertions(+), 0 deletions(-) diff --git a/kernel/futex.c b/kernel/futex.c index 1782803..06e8240 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); -- To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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