Re: [git pull] vfs.git part 1

[Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>]

On Fri, Jul 7, 2017 at 8:59 AM, Linus Torvalds
<torvalds@xxxxxxxxxxxxxxxxxxxx> wrote:
>
> The copy_flock_fields() macro has the arguments in order <from, to>,
> but all the users seem to do it the other way around.

Looking more at it, I think I'd also like copy_flock_fields() to take
pointer arguments, to match all the code around it (both
copy_to/from_user and the memset calls.

The actual order of arguments I suspect Michael's patch did better -
make the copy_flock_fields() just match the order of memcpy() and
copy_to/from_user(), both of which have <dest,src> order.

So I think my preferred patch would be something like this, even if it
is bigger than either.

Comments? Michael, does this work for your case?

              Linus

 fs/fcntl.c | 30 +++++++++++++++---------------
 1 file changed, 15 insertions(+), 15 deletions(-)

diff --git a/fs/fcntl.c b/fs/fcntl.c
index b6bd89628025..3b01b646e528 100644
--- a/fs/fcntl.c
+++ b/fs/fcntl.c
@@ -520,50 +520,50 @@ SYSCALL_DEFINE3(fcntl64, unsigned int, fd, unsigned int, cmd,
 
 #ifdef CONFIG_COMPAT
 /* careful - don't use anywhere else */
-#define copy_flock_fields(from, to)		\
-	(to).l_type = (from).l_type;		\
-	(to).l_whence = (from).l_whence;	\
-	(to).l_start = (from).l_start;		\
-	(to).l_len = (from).l_len;		\
-	(to).l_pid = (from).l_pid;
-
-static int get_compat_flock(struct flock *kfl, struct compat_flock __user *ufl)
+#define copy_flock_fields(dst, src)		\
+	(dst)->l_type = (src)->l_type;		\
+	(dst)->l_whence = (src)->l_whence;	\
+	(dst)->l_start = (src)->l_start;	\
+	(dst)->l_len = (src)->l_len;		\
+	(dst)->l_pid = (src)->l_pid;
+
+static int get_compat_flock(struct flock *kfl, const struct compat_flock __user *ufl)
 {
 	struct compat_flock fl;
 
 	if (copy_from_user(&fl, ufl, sizeof(struct compat_flock)))
 		return -EFAULT;
-	copy_flock_fields(*kfl, fl);
+	copy_flock_fields(kfl, &fl);
 	return 0;
 }
 
-static int get_compat_flock64(struct flock *kfl, struct compat_flock64 __user *ufl)
+static int get_compat_flock64(struct flock *kfl, const struct compat_flock64 __user *ufl)
 {
 	struct compat_flock64 fl;
 
 	if (copy_from_user(&fl, ufl, sizeof(struct compat_flock64)))
 		return -EFAULT;
-	copy_flock_fields(*kfl, fl);
+	copy_flock_fields(kfl, &fl);
 	return 0;
 }
 
-static int put_compat_flock(struct flock *kfl, struct compat_flock __user *ufl)
+static int put_compat_flock(const struct flock *kfl, struct compat_flock __user *ufl)
 {
 	struct compat_flock fl;
 
 	memset(&fl, 0, sizeof(struct compat_flock));
-	copy_flock_fields(fl, *kfl);
+	copy_flock_fields(&fl, kfl);
 	if (copy_to_user(ufl, &fl, sizeof(struct compat_flock)))
 		return -EFAULT;
 	return 0;
 }
 
-static int put_compat_flock64(struct flock *kfl, struct compat_flock64 __user *ufl)
+static int put_compat_flock64(const struct flock *kfl, struct compat_flock64 __user *ufl)
 {
 	struct compat_flock64 fl;
 
 	memset(&fl, 0, sizeof(struct compat_flock64));
-	copy_flock_fields(fl, *kfl);
+	copy_flock_fields(&fl, kfl);
 	if (copy_to_user(ufl, &fl, sizeof(struct compat_flock64)))
 		return -EFAULT;
 	return 0;