[PATCH 5.4 63/78] clone3: ensure copy_thread_tls is implemented

[Greg Kroah-Hartman]

From: Amanieu d'Antras <amanieu@xxxxxxxxx>

commit dd499f7a7e34270208350a849ef103c0b3ae477f upstream.

copy_thread implementations handle CLONE_SETTLS by reading the TLS
value from the registers containing the syscall arguments for
clone. This doesn't work with clone3 since the TLS value is passed
in clone_args instead.

Signed-off-by: Amanieu d'Antras <amanieu@xxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx> # 5.3.x
Link: https://lore.kernel.org/r/20200102172413.654385-8-amanieu@xxxxxxxxx
Signed-off-by: Christian Brauner <christian.brauner@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 kernel/fork.c |   10 ++++++++++
 1 file changed, 10 insertions(+)

--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -2513,6 +2513,16 @@ SYSCALL_DEFINE5(clone, unsigned long, cl
 #endif
 
 #ifdef __ARCH_WANT_SYS_CLONE3
+
+/*
+ * copy_thread implementations handle CLONE_SETTLS by reading the TLS value from
+ * the registers containing the syscall arguments for clone. This doesn't work
+ * with clone3 since the TLS value is passed in clone_args instead.
+ */
+#ifndef CONFIG_HAVE_COPY_THREAD_TLS
+#error clone3 requires copy_thread_tls support in arch
+#endif
+
 noinline static int copy_clone_args_from_user(struct kernel_clone_args *kargs,
 					      struct clone_args __user *uargs,
 					      size_t usize)