Commit 8891adc6 authored by Andy Lutomirski's avatar Andy Lutomirski Committed by Linus Torvalds
Browse files

selftests/x86/test_vsyscall: Improve the process_vm_readv() test 



The existing code accepted process_vm_readv() success or failure as long
as it didn't return garbage.  This is too weak: if the vsyscall page is
readable, then process_vm_readv() should succeed and, if the page is not
readable, then it should fail.

Signed-off-by: default avatarAndy Lutomirski <luto@kernel.org>
Signed-off-by: default avatarDave Hansen <dave.hansen@linux.intel.com>
Cc: x86@kernel.org
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Jann Horn <jannh@google.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 9fa2dd94

tools/testing/selftests/x86/test_vsyscall.c

+20 −2
Original line number Diff line number Diff line
@@ -462,6 +462,17 @@ static int test_vsys_x(void) 
	return 0;

}



/*

 * Debuggers expect ptrace() to be able to peek at the vsyscall page.

 * Use process_vm_readv() as a proxy for ptrace() to test this.  We

 * want it to work in the vsyscall=emulate case and to fail in the

 * vsyscall=xonly case.

 *

 * It's worth noting that this ABI is a bit nutty.  write(2) can't

 * read from the vsyscall page on any kernel version or mode.  The

 * fact that ptrace() ever worked was a nice courtesy of old kernels,

 * but the code to support it is fairly gross.

 */

static int test_process_vm_readv(void)

{

#ifdef __x86_64__
@@ -477,8 +488,12 @@ static int test_process_vm_readv(void) 
	remote.iov_len = 4096;

	ret = process_vm_readv(getpid(), &local, 1, &remote, 1, 0);

	if (ret != 4096) {

		printf("[OK]\tprocess_vm_readv() failed (ret = %d, errno = %d)\n", ret, errno);

		return 0;

		/*

		 * We expect process_vm_readv() to work if and only if the

		 * vsyscall page is readable.

		 */

		printf("[%s]\tprocess_vm_readv() failed (ret = %d, errno = %d)\n", vsyscall_map_r ? "FAIL" : "OK", ret, errno);

		return vsyscall_map_r ? 1 : 0;

	}



	if (vsyscall_map_r) {
@@ -488,6 +503,9 @@ static int test_process_vm_readv(void) 
			printf("[FAIL]\tIt worked but returned incorrect data\n");

			return 1;

		}

	} else {

		printf("[FAIL]\tprocess_rm_readv() succeeded, but it should have failed in this configuration\n");

		return 1;

	}

#endif

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