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 Cc: stable@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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/