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authorThomas Gleixner <tglx@linutronix.de>2010-02-02 11:40:27 +0100
committerThomas Gleixner <tglx@linutronix.de>2010-02-03 15:13:22 +0100
commit51246bfd189064079c54421507236fd2723b18f3 (patch)
tree060060ee3fe1cfe7c3ab510e4aff8a9dc3a7c64f /kernel
parent5ecb01cfdf96c5f465192bdb2a4fd4a61a24c6cc (diff)
downloadlinux-51246bfd189064079c54421507236fd2723b18f3.tar.bz2
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>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/futex.c7
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);