From: Benjamin Berg <benjamin.berg@xxxxxxxxx>
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 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 parts of it.
Signed-off-by: Benjamin Berg <benjamin.berg@xxxxxxxxx>
Fixes: 5aaeb5c01c5b ("x86/fpu, sched: Introduce CONFIG_ARCH_WANTS_DYNAMIC_TASK_STRUCT and use it on x86")
---
arch/x86/kernel/process.c | 10 +++++++++-
1 file changed, 9 insertions(+), 1 deletion(-)
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index f63f8fd00a91..1be45fe70cad 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -92,7 +92,15 @@ EXPORT_PER_CPU_SYMBOL_GPL(__tss_limit_invalid);
*/
int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src)
{
- memcpy(dst, src, arch_task_struct_size);
+ /* init_task is not dynamically sized (incomplete 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);
+ }
+
#ifdef CONFIG_VM86
dst->thread.vm86 = NULL;
#endif
--
2.47.1
