cf220ad674
As pointed out by Evgenii Stepanov one potential issue with the new ABI for enabling asymmetric is that if there are multiple places where MTE is configured in a process, some of which were compiled with the old prctl.h and some of which were compiled with the new prctl.h, there may be problems keeping track of which MTE modes are requested. For example some code may disable only sync and async modes leaving asymmetric mode enabled when it intended to fully disable MTE. In order to avoid such mishaps remove asymmetric mode from the prctl(), instead implicitly allowing it if both sync and async modes are requested. This should not disrupt userspace since a process requesting both may already see a mix of sync and async modes due to differing defaults between CPUs or changes in default while the process is running but it does mean that userspace is unable to explicitly request asymmetric mode without changing the system default for CPUs. Reported-by: Evgenii Stepanov <eugenis@google.com> Signed-off-by: Mark Brown <broonie@kernel.org> Reviewed-by: Catalin Marinas <catalin.marinas@arm.com> Reviewed-by: Evgenii Stepanov <eugenis@google.com> Cc: Peter Collingbourne <pcc@google.com> Cc: Joey Gouly <joey.gouly@arm.com> Cc: Branislav Rankov <branislav.rankov@arm.com> Link: https://lore.kernel.org/r/20220309131200.112637-1-broonie@kernel.org Signed-off-by: Will Deacon <will@kernel.org> |
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