itimers: Move compat itimer syscalls to native ones

get rid of set_fs(), sanitize compat copyin/copyout.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20170607084241.28657-12-viro@ZenIV.linux.org.uk

4 files changed, 60 insertions, 53 deletions

diff --git a/include/linux/compat.h b/include/linux/compat.h
index ecb8dd261d36..425563c7647b 100644
--- a/include/linux/compat.h
+++ b/include/linux/compat.h
@@ -94,6 +94,10 @@ struct compat_itimerval {
         struct compat_timeval   it_value;
 };
 
+struct itimerval;
+int get_compat_itimerval(struct itimerval *, const struct compat_itimerval __user *);
+int put_compat_itimerval(struct compat_itimerval __user *, const struct itimerval *);
+
 struct compat_tms {
         compat_clock_t          tms_utime;
         compat_clock_t          tms_stime;
diff --git a/kernel/compat.c b/kernel/compat.c
index 1fb8cf7e691e..c349417d2c40 100644
--- a/kernel/compat.c
+++ b/kernel/compat.c
@@ -217,65 +217,28 @@ int compat_convert_timespec(struct timespec __user **kts,
         return 0;
 }
 
-static inline long get_compat_itimerval(struct itimerval *o,
-                struct compat_itimerval __user *i)
+int get_compat_itimerval(struct itimerval *o, const struct compat_itimerval __user *i)
 {
-        return (!access_ok(VERIFY_READ, i, sizeof(*i)) ||
-                (__get_user(o->it_interval.tv_sec, &i->it_interval.tv_sec) |
-                 __get_user(o->it_interval.tv_usec, &i->it_interval.tv_usec) |
-                 __get_user(o->it_value.tv_sec, &i->it_value.tv_sec) |
-                 __get_user(o->it_value.tv_usec, &i->it_value.tv_usec)));
-}
-
-static inline long put_compat_itimerval(struct compat_itimerval __user *o,
-                struct itimerval *i)
-{
-        return (!access_ok(VERIFY_WRITE, o, sizeof(*o)) ||
-                (__put_user(i->it_interval.tv_sec, &o->it_interval.tv_sec) |
-                 __put_user(i->it_interval.tv_usec, &o->it_interval.tv_usec) |
-                 __put_user(i->it_value.tv_sec, &o->it_value.tv_sec) |
-                 __put_user(i->it_value.tv_usec, &o->it_value.tv_usec)));
-}
-
-asmlinkage long sys_ni_posix_timers(void);
-
-COMPAT_SYSCALL_DEFINE2(getitimer, int, which,
-                struct compat_itimerval __user *, it)
-{
-        struct itimerval kit;
-        int error;
-
-        if (!IS_ENABLED(CONFIG_POSIX_TIMERS))
-                return sys_ni_posix_timers();
+        struct compat_itimerval v32;
 
-        error = do_getitimer(which, &kit);
-        if (!error && put_compat_itimerval(it, &kit))
-                error = -EFAULT;
-        return error;
+        if (copy_from_user(&v32, i, sizeof(struct compat_itimerval)))
+                return -EFAULT;
+        o->it_interval.tv_sec = v32.it_interval.tv_sec;
+        o->it_interval.tv_usec = v32.it_interval.tv_usec;
+        o->it_value.tv_sec = v32.it_value.tv_sec;
+        o->it_value.tv_usec = v32.it_value.tv_usec;
+        return 0;
 }
 
-COMPAT_SYSCALL_DEFINE3(setitimer, int, which,
-                struct compat_itimerval __user *, in,
-                struct compat_itimerval __user *, out)
+int put_compat_itimerval(struct compat_itimerval __user *o, const struct itimerval *i)
 {
-        struct itimerval kin, kout;
-        int error;
+        struct compat_itimerval v32;
 
-        if (!IS_ENABLED(CONFIG_POSIX_TIMERS))
-                return sys_ni_posix_timers();
-
-        if (in) {
-                if (get_compat_itimerval(&kin, in))
-                        return -EFAULT;
-        } else
-                memset(&kin, 0, sizeof(kin));
-
-        error = do_setitimer(which, &kin, out ? &kout : NULL);
-        if (error || !out)
-                return error;
-        if (put_compat_itimerval(out, &kout))
-                return -EFAULT;
-        return 0;
+        v32.it_interval.tv_sec = i->it_interval.tv_sec;
+        v32.it_interval.tv_usec = i->it_interval.tv_usec;
+        v32.it_value.tv_sec = i->it_value.tv_sec;
+        v32.it_value.tv_usec = i->it_value.tv_usec;
+        return copy_to_user(o, &v32, sizeof(struct compat_itimerval)) ? -EFAULT : 0;
 }
 
 static compat_clock_t clock_t_to_compat_clock_t(clock_t x)
diff --git a/kernel/time/itimer.c b/kernel/time/itimer.c
index 087d6a1279b8..9dd7ff5e445a 100644
--- a/kernel/time/itimer.c
+++ b/kernel/time/itimer.c
@@ -15,6 +15,7 @@
 #include <linux/posix-timers.h>
 #include <linux/hrtimer.h>
 #include <trace/events/timer.h>
+#include <linux/compat.h>
 
 #include <linux/uaccess.h>
 
@@ -116,6 +117,19 @@ SYSCALL_DEFINE2(getitimer, int, which, struct itimerval __user *, value)
         return error;
 }
 
+#ifdef CONFIG_COMPAT
+COMPAT_SYSCALL_DEFINE2(getitimer, int, which,
+                       struct compat_itimerval __user *, it)
+{
+        struct itimerval kit;
+        int error = do_getitimer(which, &kit);
+
+        if (!error && put_compat_itimerval(it, &kit))
+                error = -EFAULT;
+        return error;
+}
+#endif
+
 
 /*
  * The timer is automagically restarted, when interval != 0
@@ -294,3 +308,27 @@ SYSCALL_DEFINE3(setitimer, int, which, struct itimerval __user *, value,
                 return -EFAULT;
         return 0;
 }
+
+#ifdef CONFIG_COMPAT
+COMPAT_SYSCALL_DEFINE3(setitimer, int, which,
+                       struct compat_itimerval __user *, in,
+                       struct compat_itimerval __user *, out)
+{
+        struct itimerval kin, kout;
+        int error;
+
+        if (in) {
+                if (get_compat_itimerval(&kin, in))
+                        return -EFAULT;
+        } else {
+                memset(&kin, 0, sizeof(kin));
+        }
+
+        error = do_setitimer(which, &kin, out ? &kout : NULL);
+        if (error || !out)
+                return error;
+        if (put_compat_itimerval(out, &kout))
+                return -EFAULT;
+        return 0;
+}
+#endif
diff --git a/kernel/time/posix-stubs.c b/kernel/time/posix-stubs.c
index f4a1962d1729..7f88517461e8 100644
--- a/kernel/time/posix-stubs.c
+++ b/kernel/time/posix-stubs.c
@@ -44,6 +44,8 @@ SYS_NI(alarm);
 COMPAT_SYS_NI(clock_adjtime);
 COMPAT_SYS_NI(timer_settime);
 COMPAT_SYS_NI(timer_gettime);
+COMPAT_SYS_NI(getitimer);
+COMPAT_SYS_NI(setitimer);
 
 /*
  * We preserve minimal support for CLOCK_REALTIME and CLOCK_MONOTONIC