x86/fpu: Avoid copying dynamic FP state from init_task in arch_dup_task_struct()

The init_task instance of struct task_struct is statically allocated and
may not contain the full FP state for userspace. As such, limit the copy
to the valid area of both init_task and 'dst' and ensure all memory is
initialized.

Note that the FP state is only needed for userspace, and as such it is
entirely reasonable for init_task to not contain parts of it.

Fixes: 5aaeb5c01c5b ("x86/fpu, sched: Introduce CONFIG_ARCH_WANTS_DYNAMIC_TASK_STRUCT and use it on x86")
Signed-off-by: Benjamin Berg <[email protected]>
Signed-off-by: Ingo Molnar <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: H. Peter Anvin <[email protected]>
Cc: Oleg Nesterov <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
----

v2:
- Fix code if arch_task_struct_size < sizeof(init_task) by using
  memcpy_and_pad.

0 files changed, 0 insertions, 0 deletions