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SubjectRe: [PATCH v12 08/22] selftests/vm: clear the bits in shadow reg when a pkey is freed.
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On 02/21/2018 05:55 PM, Ram Pai wrote:
> When a key is freed, the key is no more effective.
> Clear the bits corresponding to the pkey in the shadow
> register. Otherwise it will carry some spurious bits
> which can trigger false-positive asserts.
...
> diff --git a/tools/testing/selftests/vm/protection_keys.c b/tools/testing/selftests/vm/protection_keys.c
> index ca54a95..aaf9f09 100644
> --- a/tools/testing/selftests/vm/protection_keys.c
> +++ b/tools/testing/selftests/vm/protection_keys.c
> @@ -582,6 +582,9 @@ int alloc_pkey(void)
> int sys_pkey_free(unsigned long pkey)
> {
> int ret = syscall(SYS_pkey_free, pkey);
> +
> + if (!ret)
> + shadow_pkey_reg &= reset_bits(pkey, PKEY_DISABLE_ACCESS);
> dprintf1("%s(pkey=%ld) syscall ret: %d\n", __func__, pkey, ret);
> return ret;
> }

Did this cause problems for you in practice?

On x86, sys_pkey_free() does not affect PKRU, so this isn't quite right.
I'd much rather have the actual tests explicitly clear the PKRU bits
and also in the process clear the shadow bits.

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