fork: block invalid exit signals with clone3()

[platform/kernel/linux-rpi.git] / kernel / fork.c

diff --git a/kernel/fork.c b/kernel/fork.c
index 2852d0e..541fd80 100644 (file)
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -2338,6 +2338,8 @@ struct mm_struct *copy_init_mm(void)
  *
  * It copies the process, and if successful kick-starts
  * it and waits for it to finish using the VM if required.
+ *
+ * args->exit_signal is expected to be checked for sanity by the caller.
  */
 long _do_fork(struct kernel_clone_args *args)
 {
@@ -2562,6 +2564,14 @@ noinline static int copy_clone_args_from_user(struct kernel_clone_args *kargs,
        if (copy_from_user(&args, uargs, size))
                return -EFAULT;
 
+       /*
+        * Verify that higher 32bits of exit_signal are unset and that
+        * it is a valid signal
+        */
+       if (unlikely((args.exit_signal & ~((u64)CSIGNAL)) ||
+                    !valid_signal(args.exit_signal)))
+               return -EINVAL;
+
        *kargs = (struct kernel_clone_args){
                .flags          = args.flags,
                .pidfd          = u64_to_user_ptr(args.pidfd),