Re: [PATCH v14 22/22] selftests/vm: test correct behavior of pkey-0
From: Dave Hansen <hidden>
Date: 2018-07-18 17:03:17
Also in:
linux-arch, linux-kselftest, linux-mm
On 07/17/2018 06:49 AM, Ram Pai wrote:
quoted hunk ↗ jump to hunk
Ensure pkey-0 is allocated on start. Ensure pkey-0 can be attached dynamically in various modes, without failures. Ensure pkey-0 can be freed and allocated. Signed-off-by: Ram Pai <redacted> --- tools/testing/selftests/vm/protection_keys.c | 66 +++++++++++++++++++++++++- 1 files changed, 64 insertions(+), 2 deletions(-)diff --git a/tools/testing/selftests/vm/protection_keys.c b/tools/testing/selftests/vm/protection_keys.c index 569faf1..156b449 100644 --- a/tools/testing/selftests/vm/protection_keys.c +++ b/tools/testing/selftests/vm/protection_keys.c@@ -999,6 +999,67 @@ void close_test_fds(void) return *ptr; } +void test_pkey_alloc_free_attach_pkey0(int *ptr, u16 pkey) +{ + int i, err; + int max_nr_pkey_allocs; + int alloced_pkeys[NR_PKEYS]; + int nr_alloced = 0; + int newpkey; + long size; + + assert(pkey_last_malloc_record); + size = pkey_last_malloc_record->size; + /* + * This is a bit of a hack. But mprotect() requires + * huge-page-aligned sizes when operating on hugetlbfs. + * So, make sure that we use something that's a multiple + * of a huge page when we can. + */ + if (size >= HPAGE_SIZE) + size = HPAGE_SIZE; + + + /* allocate every possible key and make sure key-0 never got allocated */ + max_nr_pkey_allocs = NR_PKEYS; + for (i = 0; i < max_nr_pkey_allocs; i++) { + int new_pkey = alloc_pkey(); + assert(new_pkey != 0);
Missed these earlier. This needs to be pkey_assert(). We don't want these tests to ever _actually_ crash.
+ /* attach key-0 in various modes */ + err = sys_mprotect_pkey(ptr, size, PROT_READ, 0); + pkey_assert(!err); + err = sys_mprotect_pkey(ptr, size, PROT_WRITE, 0); + pkey_assert(!err); + err = sys_mprotect_pkey(ptr, size, PROT_EXEC, 0); + pkey_assert(!err); + err = sys_mprotect_pkey(ptr, size, PROT_READ|PROT_WRITE, 0); + pkey_assert(!err); + err = sys_mprotect_pkey(ptr, size, PROT_READ|PROT_WRITE|PROT_EXEC, 0); + pkey_assert(!err);
This is all fine.
+ /* free key-0 */ + err = sys_pkey_free(0); + pkey_assert(!err);
This part is called out as undefined behavior in the manpage:
An application should not call pkey_free() on any protection key
which has been assigned to an address range by pkey_mprotect(2) and
which is still in use. The behavior in this case is undefined and
may result in an error.I don't think we should be testing for undefined behavior.
quoted hunk ↗ jump to hunk
+ newpkey = sys_pkey_alloc(0, 0x0); + assert(newpkey == 0); +} + void test_read_of_write_disabled_region(int *ptr, u16 pkey) { int ptr_contents;@@ -1144,10 +1205,10 @@ void test_kernel_gup_write_to_write_disabled_region(int *ptr, u16 pkey) void test_pkey_syscalls_on_non_allocated_pkey(int *ptr, u16 pkey) { int err; - int i = get_start_key(); + int i; /* Note: 0 is the default pkey, so don't mess with it */ - for (; i < NR_PKEYS; i++) { + for (i=1; i < NR_PKEYS; i++) { if (pkey == i) continue;
This seems to be randomly reverting earlier changes.