shinys000114/linux
1
0
Fork 0
mirror of https://github.com/hardkernel/linux.git synced 2026-06-09 20:32:04 +09:00
Code Issues Packages Projects Releases Wiki Activity

futex: Handle user space corruption gracefully

Browse Source 
commit 51246bfd18 upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
This commit is contained in:
Thomas Gleixner
2010-02-02 11:40:27 +01:00
committed by Greg Kroah-Hartman
parent 5f6af116c2
commit c03d9d422d
1 changed files with 7 additions and 0 deletions
Download Patch File Download Diff File Expand all files Collapse all files

7
kernel/futex.c
View File

@@ -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;
spin_lock(&pi_state->pi_mutex.wait_lock);
new_owner = rt_mutex_next_owner(&pi_state->pi_mutex);