[PATCH 4.14 164/189] x86/pkeys/selftests: Add a test for pkey 0

Greg Kroah-Hartman
2018-06-18T08:38:30Z

From: Dave Hansen <dave.hansen@linux.intel.com>

[ Upstream commit 3488a600d90bcaf061b104dbcfbdc8d99b398312 ]

Protection key 0 is the default key for all memory and will
not normally come back from pkey_alloc(). But, you might
still want pass it to mprotect_pkey().

This check ensures that you can use pkey 0.

Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Michael Ellermen <mpe@ellerman.id.au>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ram Pai <linuxram@us.ibm.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-mm@kvack.org
Link: http://lkml.kernel.org/r/20180509171356.9E40B254@viggo.jf.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
tools/testing/selftests/x86/protection_keys.c | 30 ++++++++++++++++++++++++++
1 file changed, 30 insertions(+)

--- a/tools/testing/selftests/x86/protection_keys.c
+++ b/tools/testing/selftests/x86/protection_keys.c
@@ -1184,6 +1184,35 @@ void test_pkey_alloc_exhaust(int *ptr, u
}
}

+/*
+ * pkey 0 is special. It is allocated by default, so you do not
+ * have to call pkey_alloc() to use it first. Make sure that it
+ * is usable.
+ */
+void test_mprotect_with_pkey_0(int *ptr, u16 pkey)
+{
+ long size;
+ int prot;
+
+ 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;
+ prot = pkey_last_malloc_record->prot;
+
+ /* Use pkey 0 */
+ mprotect_pkey(ptr, size, prot, 0);
+
+ /* Make sure that we can set it back to the original pkey. */
+ mprotect_pkey(ptr, size, prot, pkey);
+}
+
void test_ptrace_of_child(int *ptr, u16 pkey)
{
__attribute__((__unused__)) int peek_result;
@@ -1378,6 +1407,7 @@ void (*pkey_tests[])(int *ptr, u16 pkey)
test_kernel_gup_write_to_write_disabled_region,
test_executing_on_unreadable_memory,
test_implicit_mprotect_exec_only_memory,
+ test_mprotect_with_pkey_0,
test_ptrace_of_child,
test_pkey_syscalls_on_non_allocated_pkey,
test_pkey_syscalls_bad_args,