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.
Signed-off-by: Thomas Gleixner <t...@linutronix.de>
Cc: sta...@vger.kernel.org
---
kernel/futex.c | 7 +++++++
1 file changed, 7 insertions(+)
Index: linux-2.6/kernel/futex.c
===================================================================
--- linux-2.6.orig/kernel/futex.c
+++ linux-2.6/kernel/futex.c
@@ -682,6 +682,8 @@ static struct task_struct * futex_find_g
p = find_task_by_vpid(pid);
if (p)
get_task_struct(p);
+ else
+ p = NULL;
rcu_read_unlock();
@@ -814,6 +816,11 @@ lookup_pi_state(u32 uval, struct futex_h
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
--
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