Re: [PATCH v14 20/22] selftests/vm: testcases must restore pkey-permissions
From: Dave Hansen <hidden>
Date: 2018-07-18 16:56:53
Also in:
linux-arch, linux-kselftest, linux-mm
On 07/17/2018 06:49 AM, Ram Pai wrote:
Generally the signal handler restores the state of the pkey register before returning. However there are times when the read/write operation can legitamely fail without invoking the signal handler. Eg: A sys_read() operaton to a write-protected page should be disallowed. In such a case the state of the pkey register is not restored to its original state. Test cases may not remember to restoring the key register state. During cleanup generically restore the key permissions.
This would, indeed be a good thing to do for a well-behaved application. But, for selftests, why does it matter what state we leave the key in? Doesn't the test itself need to establish permissions? Don't we *do* that at pkey_alloc() anyway? What problem does this solve?
quoted hunk ↗ jump to hunk
diff --git a/tools/testing/selftests/vm/protection_keys.c b/tools/testing/selftests/vm/protection_keys.c index 8a6afdd..ea3cf04 100644 --- a/tools/testing/selftests/vm/protection_keys.c +++ b/tools/testing/selftests/vm/protection_keys.c@@ -1476,8 +1476,13 @@ void run_tests_once(void) pkey_tests[test_nr](ptr, pkey); dprintf1("freeing test memory: %p\n", ptr); free_pkey_malloc(ptr); + + /* restore the permission on the key after use */ + pkey_access_allow(pkey); + pkey_write_allow(pkey); sys_pkey_free(pkey); + dprintf1("pkey_faults: %d\n", pkey_faults); dprintf1("orig_pkey_faults: %d\n", orig_pkey_faults);