Commit 8891b176 authored by Benjamin Berg's avatar Benjamin Berg Committed by Richard Weinberger
Browse files

um: avoid copying FP state from init_task 



The init_task instance of struct task_struct is statically allocated and
does not contain the dynamic area for the userspace FP registers. As
such, limit the copy to the valid area of init_task and fill the rest
with zero.

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

Reported-by: default avatarBrian Norris <briannorris@chromium.org>
Closes: https://lore.kernel.org/Z1ySXmjZm-xOqk90@google.com


Fixes: 3f17fed2 ("um: switch to regset API and depend on XSTATE")
Signed-off-by: default avatarBenjamin Berg <benjamin.berg@intel.com>
Link: https://patch.msgid.link/20241217202745.1402932-3-benjamin@sipsolutions.net


Signed-off-by: default avatarJohannes Berg <johannes.berg@intel.com>
Signed-off-by: default avatarRichard Weinberger <richard@nod.at>
parent 5298b7cf

arch/um/kernel/process.c

+9 −1
Original line number Diff line number Diff line
@@ -191,7 +191,15 @@ void initial_thread_cb(void (*proc)(void *), void *arg) 
int arch_dup_task_struct(struct task_struct *dst,

			 struct task_struct *src)

{

	/* init_task is not dynamically sized (missing FPU state) */

	if (unlikely(src == &init_task)) {

		memcpy(dst, src, sizeof(init_task));

		memset((void *)dst + sizeof(init_task), 0,

		       arch_task_struct_size - sizeof(init_task));

	} else {

		memcpy(dst, src, arch_task_struct_size);

	}



	return 0;

}