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

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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: e12310a0d3 ("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>
This commit is contained in:
Mark Brown 2023-08-03 00:46:39 +01:00 committed by Catalin Marinas
parent 003e6b56d7
commit c9bb40b7f7
1 changed files with 1 additions and 1 deletions
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2
arch/arm64/kernel/fpsimd.c
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@ -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;
}
}