arm64: fpsimd: Avoid FPSIMD context leakage for the init task

The init task is started with thread_flags equal to 0, which means
that TIF_FOREIGN_FPSTATE is initially clear.

It is theoretically possible (if unlikely) that the init task could
reach userspace without ever being scheduled out.  If this occurs,
data left in the FPSIMD registers by the kernel could be exposed.

This patch fixes this anomaly by ensuring that the init task's
initial TIF_FOREIGN_FPSTATE is set.

Signed-off-by: Dave Martin <[email protected]>
Fixes: 005f78cd8849 ("arm64: defer reloading a task's FPSIMD state to userland resume")
Reviewed-by: Catalin Marinas <[email protected]>
Reviewed-by: Alex Bennée <[email protected]>
Cc: Will Deacon <[email protected]>
Cc: Ard Biesheuvel <[email protected]>
Signed-off-by: Marc Zyngier <[email protected]>

0 files changed, 0 insertions, 0 deletions