[LTP] [PATCH v2] syscalls/ptrace07: new test for ptrace FPU state corruption
Eric Biggers
ebiggers3@gmail.com
Mon Oct 16 23:12:07 CEST 2017
From: Eric Biggers <ebiggers@google.com>
Add a test for a bug which allowed a task to be assigned an invalid FPU
state, causing the FPU registers to not be restored on context switch.
Signed-off-by: Eric Biggers <ebiggers@google.com>
---
runtest/syscalls | 1 +
testcases/kernel/syscalls/.gitignore | 1 +
testcases/kernel/syscalls/ptrace/ptrace07.c | 167 ++++++++++++++++++++++++++++
3 files changed, 169 insertions(+)
create mode 100644 testcases/kernel/syscalls/ptrace/ptrace07.c
diff --git a/runtest/syscalls b/runtest/syscalls
index 49ae48621..c2f4921ef 100644
--- a/runtest/syscalls
+++ b/runtest/syscalls
@@ -843,6 +843,7 @@ ptrace04 ptrace04
ptrace05 ptrace05
# Broken test; See: testcases/kernel/syscalls/ptrace/Makefile for more details.
#ptrace06 ptrace06
+ptrace07 ptrace07
pwrite01 pwrite01
pwrite02 pwrite02
diff --git a/testcases/kernel/syscalls/.gitignore b/testcases/kernel/syscalls/.gitignore
index 76bae9e4a..5b9c5d93f 100644
--- a/testcases/kernel/syscalls/.gitignore
+++ b/testcases/kernel/syscalls/.gitignore
@@ -705,6 +705,7 @@
/ptrace/ptrace03
/ptrace/ptrace04
/ptrace/ptrace05
+/ptrace/ptrace07
/ptrace/simple_tracer
/pwrite/f
/pwrite/pwrite01
diff --git a/testcases/kernel/syscalls/ptrace/ptrace07.c b/testcases/kernel/syscalls/ptrace/ptrace07.c
new file mode 100644
index 000000000..d634c8a8d
--- /dev/null
+++ b/testcases/kernel/syscalls/ptrace/ptrace07.c
@@ -0,0 +1,167 @@
+/*
+ * Copyright (c) 2017 Google, Inc.
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program, if not, see <http://www.gnu.org/licenses/>.
+ */
+
+/*
+ * Regression test for commit 814fb7bb7db5 ("x86/fpu: Don't let userspace set
+ * bogus xcomp_bv"). This bug allowed ptrace(pid, PTRACE_SETREGSET,
+ * NT_X86_XSTATE, &iov) to assign a task an invalid FPU state --- specifically,
+ * by setting reserved bits in xstate_header.xcomp_bv. This made restoring the
+ * FPU registers fail when switching to the task, causing the FPU registers to
+ * take on the values from other tasks.
+ *
+ * This test works firstly by checking whether PTRACE_SETREGSET fails with
+ * EINVAL when trying to set the invalid FPU state of a subprocess.
+ *
+ * In addition, this test has the subprocess run a loop checking its xmm0
+ * register for corruption. This detects the case where the FPU state became
+ * invalid and the kernel is not restoring the process's registers. Note that
+ * we have to set the expected value of xmm0 to all 0's since it is acceptable
+ * behavior for the kernel to simply reinitialize the FPU state upon seeing that
+ * it is invalid. To increase the chance of detecting the problem, we also
+ * create additional processes that spin with different xmm0 contents.
+ *
+ * Thus bug affected the x86 architecture only. Other architectures could have
+ * similar bugs as well, but this test has to be x86-specific because it has to
+ * know about the architecture-dependent FPU state.
+ */
+
+#include <errno.h>
+#include <inttypes.h>
+#include <sched.h>
+#include <stdbool.h>
+#include <stdlib.h>
+#include <sys/uio.h>
+
+#include "config.h"
+#include "ptrace.h"
+#include "tst_test.h"
+
+#ifndef PTRACE_GETREGSET
+# define PTRACE_GETREGSET 0x4204
+#endif
+
+#ifndef PTRACE_SETREGSET
+# define PTRACE_SETREGSET 0x4205
+#endif
+
+#ifndef NT_X86_XSTATE
+# define NT_X86_XSTATE 0x202
+#endif
+
+#ifdef __x86_64__
+static void check_regs_loop(uint32_t initval)
+{
+ const unsigned long num_iters = 1000000000;
+ uint32_t xmm0[4] = { initval, initval, initval, initval };
+ int status = 1;
+
+ asm volatile(" movdqu %0, %%xmm0\n"
+ " mov %0, %%rbx\n"
+ "1: dec %2\n"
+ " jz 2f\n"
+ " movdqu %%xmm0, %0\n"
+ " mov %0, %%rax\n"
+ " cmp %%rax, %%rbx\n"
+ " je 1b\n"
+ " jmp 3f\n"
+ "2: mov $0, %1\n"
+ "3:\n"
+ : "+m" (xmm0), "+r" (status)
+ : "r" (num_iters) : "rax", "rbx", "xmm0");
+
+ if (status) {
+ tst_res(TFAIL,
+ "xmm registers corrupted! initval=%08X, xmm0=%08X%08X%08X%08X\n",
+ initval, xmm0[0], xmm0[1], xmm0[2], xmm0[3]);
+ }
+ exit(status);
+}
+
+static void do_test(void)
+{
+ int i;
+ int num_cpus = tst_ncpus();
+ pid_t pid;
+ uint64_t xstate[512];
+ struct iovec iov = { .iov_base = xstate, .iov_len = sizeof(xstate) };
+ int status;
+ bool okay = true;
+
+ pid = SAFE_FORK();
+ if (pid == 0) {
+ TST_CHECKPOINT_WAKE(0);
+ check_regs_loop(0x00000000);
+ }
+ for (i = 0; i < num_cpus; i++) {
+ if (SAFE_FORK() == 0)
+ check_regs_loop(0xDEADBEEF);
+ }
+
+ TST_CHECKPOINT_WAIT(0);
+ sched_yield();
+
+ TEST(ptrace(PTRACE_ATTACH, pid, 0, 0));
+ if (TEST_RETURN != 0)
+ tst_brk(TBROK | TTERRNO, "PTRACE_ATTACH failed");
+
+ SAFE_WAITPID(pid, NULL, 0);
+ TEST(ptrace(PTRACE_GETREGSET, pid, NT_X86_XSTATE, &iov));
+ if (TEST_RETURN != 0) {
+ if (TEST_ERRNO == EIO)
+ tst_brk(TCONF, "GETREGSET/SETREGSET is unsupported");
+
+ if (TEST_ERRNO == EINVAL)
+ tst_brk(TCONF, "NT_X86_XSTATE is unsupported");
+
+ if (TEST_ERRNO == ENODEV)
+ tst_brk(TCONF, "CPU doesn't support XSAVE instruction");
+
+ tst_brk(TBROK | TTERRNO,
+ "PTRACE_GETREGSET failed with unexpected error");
+ }
+
+ xstate[65] = -1; /* sets all bits in xstate_header.xcomp_bv */
+ TEST(ptrace(PTRACE_SETREGSET, pid, NT_X86_XSTATE, &iov));
+ if (TEST_RETURN == 0) {
+ tst_res(TFAIL, "PTRACE_SETREGSET unexpectedly succeeded");
+ okay = false;
+ } else if (TEST_ERRNO != EINVAL) {
+ tst_brk(TBROK | TTERRNO,
+ "PTRACE_SETREGSET failed with unexpected error");
+ }
+
+ TEST(ptrace(PTRACE_CONT, pid, 0, 0));
+ if (TEST_RETURN != 0)
+ tst_brk(TBROK | TTERRNO, "PTRACE_CONT failed");
+
+ for (i = 0; i < num_cpus + 1; i++) {
+ SAFE_WAIT(&status);
+ okay &= (WIFEXITED(status) && WEXITSTATUS(status) == 0);
+ }
+ if (okay)
+ tst_res(TPASS, "wasn't able to set invalid FPU state");
+}
+
+static struct tst_test test = {
+ .test_all = do_test,
+ .forks_child = 1,
+ .needs_checkpoints = 1,
+};
+
+#else /* !__x86_64__ */
+ TST_TEST_TCONF("this test is only supported on x86_64");
+#endif /* __x86_64__ */
--
2.15.0.rc0.271.g36b669edcc-goog
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