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futex: Prevent attaching to kernel threads 

We happily allow userspace to declare a random kernel thread to be the
owner of a user space PI futex.

Found while analysing the fallout of Dave Jones syscall fuzzer.

We also should validate the thread group for private futexes and find
some fast way to validate whether the "alleged" owner has RW access on
the file which backs the SHM, but that's a separate issue.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Dave Jones <davej@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Darren Hart <darren@dvhart.com>
Cc: Davidlohr Bueso <davidlohr@hp.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Clark Williams <williams@redhat.com>
Cc: Paul McKenney <paulmck@linux.vnet.ibm.com>
Cc: Lai Jiangshan <laijs@cn.fujitsu.com>
Cc: Roland McGrath <roland@hack.frob.com>
Cc: Carlos ODonell <carlos@redhat.com>
Cc: Jakub Jelinek <jakub@redhat.com>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Link: http://lkml.kernel.org/r/20140512201701.194824402@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
This commit is contained in:
Thomas Gleixner 2014-05-12 20:45:35 +00:00
parent 866293ee54
commit f0d71b3dcb
1 changed files with 5 additions and 0 deletions
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5
kernel/futex.c
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@ -814,6 +814,11 @@ lookup_pi_state(u32 uval, struct futex_hash_bucket *hb,
if (!p) if (!p)
return -ESRCH; return -ESRCH;
if (!p->mm) {
put_task_struct(p);
return -EPERM;
}
/* /*
* We need to look at the task state flags to figure out, * We need to look at the task state flags to figure out,
* whether the task is exiting. To protect against the do_exit * whether the task is exiting. To protect against the do_exit