[PATCH 6.1 091/127] arm64/fpsimd: Clear SME state in the target task when setting the VL

Greg Kroah-Hartman
2023-08-09T10:55:27Z

From: Mark Brown <broonie@kernel.org>

commit c9bb40b7f786662e33d71afe236442b0b61f0446 upstream.

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: e12310a0d30f ("arm64/sme: Implement ptrace support for streaming mode SVE registers")
Reported-by: David Spickett <David.Spickett@arm.com>
Signed-off-by: Mark 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: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
arch/arm64/kernel/fpsimd.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/arch/arm64/kernel/fpsimd.c
+++ b/arch/arm64/kernel/fpsimd.c
@@ -864,7 +864,7 @@ int vec_set_vector_length(struct task_st
*/
task->thread.svcr &= ~(SVCR_SM_MASK |
SVCR_ZA_MASK);
- clear_thread_flag(TIF_SME);
+ clear_tsk_thread_flag(task, TIF_SME);
free_sme = true;
}
}