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Message-Id: <b413397c804265f8865f3e70b14b09485ea7c314.1561610354.git.luto@kernel.org>
Date: Wed, 26 Jun 2019 21:45:06 -0700
From: Andy Lutomirski <luto@...nel.org>
To: x86@...nel.org
Cc: LKML <linux-kernel@...r.kernel.org>,
Kees Cook <keescook@...omium.org>,
Florian Weimer <fweimer@...hat.com>,
Jann Horn <jannh@...gle.com>,
Andy Lutomirski <luto@...nel.org>,
Borislav Petkov <bp@...en8.de>,
Kernel Hardening <kernel-hardening@...ts.openwall.com>,
Peter Zijlstra <peterz@...radead.org>,
Thomas Gleixner <tglx@...utronix.de>
Subject: [PATCH v2 5/8] selftests/x86/vsyscall: Verify that vsyscall=none blocks execution
If vsyscall=none accidentally still allowed vsyscalls, the test
wouldn't fail. Fix it.
Cc: Kees Cook <keescook@...omium.org>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Kernel Hardening <kernel-hardening@...ts.openwall.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Signed-off-by: Andy Lutomirski <luto@...nel.org>
---
tools/testing/selftests/x86/test_vsyscall.c | 76 ++++++++++++++-------
1 file changed, 52 insertions(+), 24 deletions(-)
diff --git a/tools/testing/selftests/x86/test_vsyscall.c b/tools/testing/selftests/x86/test_vsyscall.c
index 4c9a8d76dba0..34a1d35995ef 100644
--- a/tools/testing/selftests/x86/test_vsyscall.c
+++ b/tools/testing/selftests/x86/test_vsyscall.c
@@ -49,21 +49,21 @@ static void sethandler(int sig, void (*handler)(int, siginfo_t *, void *),
}
/* vsyscalls and vDSO */
-bool should_read_vsyscall = false;
+bool vsyscall_map_r = false, vsyscall_map_x = false;
typedef long (*gtod_t)(struct timeval *tv, struct timezone *tz);
-gtod_t vgtod = (gtod_t)VSYS(0xffffffffff600000);
+const gtod_t vgtod = (gtod_t)VSYS(0xffffffffff600000);
gtod_t vdso_gtod;
typedef int (*vgettime_t)(clockid_t, struct timespec *);
vgettime_t vdso_gettime;
typedef long (*time_func_t)(time_t *t);
-time_func_t vtime = (time_func_t)VSYS(0xffffffffff600400);
+const time_func_t vtime = (time_func_t)VSYS(0xffffffffff600400);
time_func_t vdso_time;
typedef long (*getcpu_t)(unsigned *, unsigned *, void *);
-getcpu_t vgetcpu = (getcpu_t)VSYS(0xffffffffff600800);
+const getcpu_t vgetcpu = (getcpu_t)VSYS(0xffffffffff600800);
getcpu_t vdso_getcpu;
static void init_vdso(void)
@@ -107,7 +107,7 @@ static int init_vsys(void)
maps = fopen("/proc/self/maps", "r");
if (!maps) {
printf("[WARN]\tCould not open /proc/self/maps -- assuming vsyscall is r-x\n");
- should_read_vsyscall = true;
+ vsyscall_map_r = true;
return 0;
}
@@ -133,12 +133,8 @@ static int init_vsys(void)
}
printf("\tvsyscall permissions are %c-%c\n", r, x);
- should_read_vsyscall = (r == 'r');
- if (x != 'x') {
- vgtod = NULL;
- vtime = NULL;
- vgetcpu = NULL;
- }
+ vsyscall_map_r = (r == 'r');
+ vsyscall_map_x = (x == 'x');
found = true;
break;
@@ -148,10 +144,8 @@ static int init_vsys(void)
if (!found) {
printf("\tno vsyscall map in /proc/self/maps\n");
- should_read_vsyscall = false;
- vgtod = NULL;
- vtime = NULL;
- vgetcpu = NULL;
+ vsyscall_map_r = false;
+ vsyscall_map_x = false;
}
return nerrs;
@@ -242,7 +236,7 @@ static int test_gtod(void)
err(1, "syscall gettimeofday");
if (vdso_gtod)
ret_vdso = vdso_gtod(&tv_vdso, &tz_vdso);
- if (vgtod)
+ if (vsyscall_map_x)
ret_vsys = vgtod(&tv_vsys, &tz_vsys);
if (sys_gtod(&tv_sys2, &tz_sys) != 0)
err(1, "syscall gettimeofday");
@@ -256,7 +250,7 @@ static int test_gtod(void)
}
}
- if (vgtod) {
+ if (vsyscall_map_x) {
if (ret_vsys == 0) {
nerrs += check_gtod(&tv_sys1, &tv_sys2, &tz_sys, "vsyscall", &tv_vsys, &tz_vsys);
} else {
@@ -277,7 +271,7 @@ static int test_time(void) {
t_sys1 = sys_time(&t2_sys1);
if (vdso_time)
t_vdso = vdso_time(&t2_vdso);
- if (vtime)
+ if (vsyscall_map_x)
t_vsys = vtime(&t2_vsys);
t_sys2 = sys_time(&t2_sys2);
if (t_sys1 < 0 || t_sys1 != t2_sys1 || t_sys2 < 0 || t_sys2 != t2_sys2) {
@@ -298,7 +292,7 @@ static int test_time(void) {
}
}
- if (vtime) {
+ if (vsyscall_map_x) {
if (t_vsys < 0 || t_vsys != t2_vsys) {
printf("[FAIL]\tvsyscall failed (ret:%ld output:%ld)\n", t_vsys, t2_vsys);
nerrs++;
@@ -334,7 +328,7 @@ static int test_getcpu(int cpu)
ret_sys = sys_getcpu(&cpu_sys, &node_sys, 0);
if (vdso_getcpu)
ret_vdso = vdso_getcpu(&cpu_vdso, &node_vdso, 0);
- if (vgetcpu)
+ if (vsyscall_map_x)
ret_vsys = vgetcpu(&cpu_vsys, &node_vsys, 0);
if (ret_sys == 0) {
@@ -373,7 +367,7 @@ static int test_getcpu(int cpu)
}
}
- if (vgetcpu) {
+ if (vsyscall_map_x) {
if (ret_vsys) {
printf("[FAIL]\tvsyscall getcpu() failed\n");
nerrs++;
@@ -414,10 +408,10 @@ static int test_vsys_r(void)
can_read = false;
}
- if (can_read && !should_read_vsyscall) {
+ if (can_read && !vsyscall_map_r) {
printf("[FAIL]\tWe have read access, but we shouldn't\n");
return 1;
- } else if (!can_read && should_read_vsyscall) {
+ } else if (!can_read && vsyscall_map_r) {
printf("[FAIL]\tWe don't have read access, but we should\n");
return 1;
} else if (can_read) {
@@ -431,6 +425,39 @@ static int test_vsys_r(void)
return 0;
}
+static int test_vsys_x(void)
+{
+#ifdef __x86_64__
+ if (vsyscall_map_x) {
+ /* We already tested this adequately. */
+ return 0;
+ }
+
+ printf("[RUN]\tMake sure that vsyscalls really page fault\n");
+
+ bool can_exec;
+ if (sigsetjmp(jmpbuf, 1) == 0) {
+ vgtod(NULL, NULL);
+ can_exec = true;
+ } else {
+ can_exec = false;
+ }
+
+ if (can_exec) {
+ printf("[FAIL]\tExecuting the vsyscall did not page fault\n");
+ return 1;
+ } else if (segv_err & (1 << 4)) { /* INSTR */
+ printf("[OK]\tExecuting the vsyscall page failed: #PF(0x%lx)\n",
+ segv_err);
+ } else {
+ printf("[FAILT]\tExecution failed with the wrong error: #PF(0x%lx)\n",
+ segv_err);
+ return 1;
+ }
+#endif
+
+ return 0;
+}
#ifdef __x86_64__
#define X86_EFLAGS_TF (1UL << 8)
@@ -462,7 +489,7 @@ static int test_emulation(void)
time_t tmp;
bool is_native;
- if (!vtime)
+ if (!vsyscall_map_x)
return 0;
printf("[RUN]\tchecking that vsyscalls are emulated\n");
@@ -504,6 +531,7 @@ int main(int argc, char **argv)
sethandler(SIGSEGV, sigsegv, 0);
nerrs += test_vsys_r();
+ nerrs += test_vsys_x();
#ifdef __x86_64__
nerrs += test_emulation();
--
2.21.0
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