6.13-stable review patch. If anyone has any objections, please let me know. ------------------ From: Benjamin Berg <benjamin.berg@xxxxxxxxx> [ Upstream commit 8891b176d350ec5ea9a39c6ef4c99bd63d68e64c ] 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@xxxxxxxxxxxx> Closes: https://lore.kernel.org/Z1ySXmjZm-xOqk90@xxxxxxxxxx Fixes: 3f17fed21491 ("um: switch to regset API and depend on XSTATE") Signed-off-by: Benjamin Berg <benjamin.berg@xxxxxxxxx> Link: https://patch.msgid.link/20241217202745.1402932-3-benjamin@xxxxxxxxxxxxxxxx Signed-off-by: Johannes Berg <johannes.berg@xxxxxxxxx> Signed-off-by: Richard Weinberger <richard@xxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> --- arch/um/kernel/process.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/arch/um/kernel/process.c b/arch/um/kernel/process.c index 30bdc0a87dc85..3a67ba8aa62dc 100644 --- a/arch/um/kernel/process.c +++ b/arch/um/kernel/process.c @@ -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; } -- 2.39.5
