Commit c9bb40b7 authored by Mark Brown's avatar Mark Brown Committed by Catalin Marinas
Browse files

arm64/fpsimd: Clear SME state in the target task when setting the VL 



When setting SME vector lengths we clear TIF_SME to reenable SME traps,
doing a reallocation of the backing storage on next use. We do this using
clear_thread_flag() which operates on the current thread, meaning that when
setting the vector length via ptrace we may both not force traps for the
target task and force a spurious flush of any SME state that the tracing
task may have.

Clear the flag in the target task.

Fixes: e12310a0 ("arm64/sme: Implement ptrace support for streaming mode SVE registers")
Reported-by: default avatarDavid Spickett <David.Spickett@arm.com>
Signed-off-by: default avatarMark Brown <broonie@kernel.org>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20230803-arm64-fix-ptrace-tif-sme-v1-1-88312fd6fbfd@kernel.org


Signed-off-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
parent 003e6b56

arch/arm64/kernel/fpsimd.c

+1 −1
Original line number Diff line number Diff line
@@ -909,7 +909,7 @@ int vec_set_vector_length(struct task_struct *task, enum vec_type type, 
			 */

			task->thread.svcr &= ~(SVCR_SM_MASK |

					       SVCR_ZA_MASK);

			clear_thread_flag(TIF_SME);

			clear_tsk_thread_flag(task, TIF_SME);

			free_sme = true;

		}

	}