compat: Get rid of (get|put)_compat_time(val|spec)

We have two APIs for compatiblity timespec/val, with confusingly
similar names.  compat_(get|put)_time(val|spec) *do* handle the case
where COMPAT_USE_64BIT_TIME is set, whereas
(get|put)_compat_time(val|spec) do not.  This is an accident waiting
to happen.

Clean it up by favoring the full-service version; the limited version
is replaced with double-underscore versions static to kernel/compat.c.

A common pattern is to convert a struct timespec to kernel format in
an allocation on the user stack.  Unfortunately it is open-coded in
several places.  Since this allocation isn't actually needed if
COMPAT_USE_64BIT_TIME is true (since user format == kernel format)
encapsulate that whole pattern into the function
compat_convert_timespec().  An equivalent function should be written
for struct timeval if it is needed in the future.

Finally, get rid of compat_(get|put)_timeval_convert(): each was only
used once, and the latter was not even doing what the function said
(no conversion actually was being done.)  Moving the conversion into
compat_sys_settimeofday() itself makes the code much more similar to
sys_settimeofday() itself.

v3: Remove unused compat_convert_timeval().

v2: Drop bogus "const" in the destination argument for
    compat_convert_time*().

Cc: Mauro Carvalho Chehab <[email protected]>
Cc: Alexander Viro <[email protected]>
Cc: Hans Verkuil <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: Heiko Carstens <[email protected]>
Cc: Manfred Spraul <[email protected]>
Cc: Mateusz Guzik <[email protected]>
Cc: Rafael Aquini <[email protected]>
Cc: Davidlohr Bueso <[email protected]>
Cc: Stephen Rothwell <[email protected]>
Cc: Dan Carpenter <[email protected]>
Cc: Arnd Bergmann <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Catalin Marinas <[email protected]>
Cc: Will Deacon <[email protected]>
Tested-by: H.J. Lu <[email protected]>
Signed-off-by: H. Peter Anvin <[email protected]>

drivers/media/v4l2-core/v4l2-compat-ioctl32.c

@@ -733,7 +733,7 @@ static int put_v4l2_event32(struct v4l2_event *kp, struct v4l2_event32 __user *u
 		copy_to_user(&up->u, &kp->u, sizeof(kp->u)) ||
 		put_user(kp->pending, &up->pending) ||
 		put_user(kp->sequence, &up->sequence) ||
-		put_compat_timespec(&kp->timestamp, &up->timestamp) ||
+		compat_put_timespec(&kp->timestamp, &up->timestamp) ||
 		put_user(kp->id, &up->id) ||
 		copy_to_user(up->reserved, kp->reserved, 8 * sizeof(__u32)))
 			return -EFAULT;

fs/compat.c

@@ -92,8 +92,8 @@ asmlinkage long compat_sys_utimensat(unsigned int dfd, const char __user *filena
 	struct timespec tv[2];
 
 	if  (t) {
-		if (get_compat_timespec(&tv[0], &t[0]) ||
-		    get_compat_timespec(&tv[1], &t[1]))
+		if (compat_get_timespec(&tv[0], &t[0]) ||
+		    compat_get_timespec(&tv[1], &t[1]))
 			return -EFAULT;
 
 		if (tv[0].tv_nsec == UTIME_OMIT && tv[1].tv_nsec == UTIME_OMIT)
@@ -512,7 +512,7 @@ compat_sys_io_getevents(aio_context_t ctx_id,
 				nr * sizeof(struct io_event))))
 		goto out;
 	if (timeout) {
-		if (get_compat_timespec(&t, timeout))
+		if (compat_get_timespec(&t, timeout))
 			goto out;
 
 		ut = compat_alloc_user_space(sizeof(*ut));

include/linux/compat.h

@@ -140,27 +140,24 @@ struct compat_sigaction {
 	compat_sigset_t			sa_mask __packed;
 };
 
-/*
- * These functions operate strictly on struct compat_time*
- */
-extern int get_compat_timespec(struct timespec *,
-			       const struct compat_timespec __user *);
-extern int put_compat_timespec(const struct timespec *,
-			       struct compat_timespec __user *);
-extern int get_compat_timeval(struct timeval *,
-			      const struct compat_timeval __user *);
-extern int put_compat_timeval(const struct timeval *,
-			      struct compat_timeval __user *);
 /*
  * These functions operate on 32- or 64-bit specs depending on
- * COMPAT_USE_64BIT_TIME, hence the void user pointer arguments and the
- * naming as compat_get/put_ rather than get/put_compat_.
+ * COMPAT_USE_64BIT_TIME, hence the void user pointer arguments.
  */
 extern int compat_get_timespec(struct timespec *, const void __user *);
 extern int compat_put_timespec(const struct timespec *, void __user *);
 extern int compat_get_timeval(struct timeval *, const void __user *);
 extern int compat_put_timeval(const struct timeval *, void __user *);
 
+/*
+ * This function convert a timespec if necessary and returns a *user
+ * space* pointer.  If no conversion is necessary, it returns the
+ * initial pointer.  NULL is a legitimate argument and will always
+ * output NULL.
+ */
+extern int compat_convert_timespec(struct timespec __user **,
+				   const void __user *);
+
 struct compat_iovec {
 	compat_uptr_t	iov_base;
 	compat_size_t	iov_len;

ipc/compat.c

@@ -752,14 +752,8 @@ long compat_sys_shmctl(int first, int second, void __user *uptr)
 long compat_sys_semtimedop(int semid, struct sembuf __user *tsems,
 		unsigned nsops, const struct compat_timespec __user *timeout)
 {
-	struct timespec __user *ts64 = NULL;
-	if (timeout) {
-		struct timespec ts;
-		ts64 = compat_alloc_user_space(sizeof(*ts64));
-		if (get_compat_timespec(&ts, timeout))
-			return -EFAULT;
-		if (copy_to_user(ts64, &ts, sizeof(ts)))
-			return -EFAULT;
-	}
+	struct timespec __user *ts64;
+	if (compat_convert_timespec(&ts64, timeout))
+		return -EFAULT;
 	return sys_semtimedop(semid, tsems, nsops, ts64);
 }

ipc/compat_mq.c

@@ -64,28 +64,14 @@ asmlinkage long compat_sys_mq_open(const char __user *u_name,
 	return sys_mq_open(u_name, oflag, mode, p);
 }
 
-static int compat_prepare_timeout(struct timespec __user **p,
-				  const struct compat_timespec __user *u)
-{
-	struct timespec ts;
-	if (!u) {
-		*p = NULL;
-		return 0;
-	}
-	*p = compat_alloc_user_space(sizeof(ts));
-	if (get_compat_timespec(&ts, u) || copy_to_user(*p, &ts, sizeof(ts)))
-		return -EFAULT;
-	return 0;
-}
-
 asmlinkage long compat_sys_mq_timedsend(mqd_t mqdes,
 			const char __user *u_msg_ptr,
 			size_t msg_len, unsigned int msg_prio,
 			const struct compat_timespec __user *u_abs_timeout)
 {
 	struct timespec __user *u_ts;
 
-	if (compat_prepare_timeout(&u_ts, u_abs_timeout))
+	if (compat_convert_timespec(&u_ts, u_abs_timeout))
 		return -EFAULT;
 
 	return sys_mq_timedsend(mqdes, u_msg_ptr, msg_len,
@@ -98,7 +84,8 @@ asmlinkage ssize_t compat_sys_mq_timedreceive(mqd_t mqdes,
 			const struct compat_timespec __user *u_abs_timeout)
 {
 	struct timespec __user *u_ts;
-	if (compat_prepare_timeout(&u_ts, u_abs_timeout))
+
+	if (compat_convert_timespec(&u_ts, u_abs_timeout))
 		return -EFAULT;
 
 	return sys_mq_timedreceive(mqdes, u_msg_ptr, msg_len,