diff options
authorThomas Gleixner <tglx@linutronix.de>2014-05-12 20:45:35 +0000
committerWilly Tarreau <w@1wt.eu>2014-06-19 00:25:57 +0200
commit129af2db18d8d85497b1fa766553d63717876578 (patch)
parent81ce5f0cae0c15d679fef2219414bb508c9c1873 (diff)
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 (cherry picked from commit f0d71b3dcb8332f7971b5f2363632573e6d9486a) Signed-off-by: Willy Tarreau <w@1wt.eu>
1 files changed, 5 insertions, 0 deletions
diff --git a/kernel/futex.c b/kernel/futex.c
index 731b2714e2ba..c00b6e400b7d 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -610,6 +610,11 @@ lookup_pi_state(u32 uval, struct futex_hash_bucket *hb,
if (!p)
return -ESRCH;
+ if (!p->mm) {
+ put_task_struct(p);
+ return -EPERM;
+ }
* We need to look at the task state flags to figure out,
* whether the task is exiting. To protect against the do_exit