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um: avoid copying FP state from init_task

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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: Brian Norris <briannorris@chromium.org>
Closes: https://lore.kernel.org/Z1ySXmjZm-xOqk90@google.com
Fixes: 3f17fed214 ("um: switch to regset API and depend on XSTATE")
Signed-off-by: Benjamin Berg <benjamin.berg@intel.com>
Link: https://patch.msgid.link/20241217202745.1402932-3-benjamin@sipsolutions.net
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Richard Weinberger <richard@nod.at>
This commit is contained in:
Benjamin Berg 2024-12-17 21:27:44 +01:00 • committed by Richard Weinberger
parent 5298b7cffa
commit 8891b176d3
1 changed files with 9 additions and 1 deletions
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10
arch/um/kernel/process.c
View file

@ -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)
{
memcpy(dst, src, arch_task_struct_size);
/* 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;
}