Re: [RFC][PATCH 10/13] get rid of audit_reusename()

[Al Viro <viro@zeniv.linux.org.uk>]

On Mon, Nov 10, 2025 at 08:41:45AM -0800, Linus Torvalds wrote:

> > IMO things like "xfs" or "ceph" don't look like pathnames - if
> > anything, we ought to use copy_mount_string() for consistency with
> > mount(2)...
> 
> Oh, absolutely not.
> 
> But that code certainly could just do strndup_user(). That's the
> normal thing for "get a string from user space" these days, but it
> didn't historically exist..

There would be a minor change in errors (s/ENAMETOOLONG/EINVAL/
and s/ENOENT/EINVAL/, AFAICS), but nobody really gives a damn,
so...

If we go that way, do you see any problems with treating
osf_{ufs,cdfs}_mount() in the same manner?  Yes, these are pathnames,
but the strings copied there are going to be fed (after another round
of copying) to lookup_bdev(), i.e. getname_kernel().  At least that
way it would be consistent with what mount(2) does...

diff --git a/arch/alpha/kernel/osf_sys.c b/arch/alpha/kernel/osf_sys.c
index a08e8edef1a4..21a8f985999b 100644
--- a/arch/alpha/kernel/osf_sys.c
+++ b/arch/alpha/kernel/osf_sys.c
@@ -454,42 +454,34 @@ static int
 osf_ufs_mount(const char __user *dirname,
 	      struct ufs_args __user *args, int flags)
 {
-	int retval;
+	char *devname __free(kfree) = NULL;
 	struct cdfs_args tmp;
-	struct filename *devname;
 
-	retval = -EFAULT;
 	if (copy_from_user(&tmp, args, sizeof(tmp)))
-		goto out;
-	devname = getname(tmp.devname);
-	retval = PTR_ERR(devname);
+		return -EFAULT;
+
+	devname = strndup_user(tmp.devname, PATH_MAX);
 	if (IS_ERR(devname))
-		goto out;
-	retval = do_mount(devname->name, dirname, "ext2", flags, NULL);
-	putname(devname);
- out:
-	return retval;
+		return PTR_ERR(devname);
+
+	return do_mount(devname, dirname, "ext2", flags, NULL);
 }
 
 static int
 osf_cdfs_mount(const char __user *dirname,
 	       struct cdfs_args __user *args, int flags)
 {
-	int retval;
+	char *devname __free(kfree) = NULL;
 	struct cdfs_args tmp;
-	struct filename *devname;
 
-	retval = -EFAULT;
 	if (copy_from_user(&tmp, args, sizeof(tmp)))
-		goto out;
-	devname = getname(tmp.devname);
-	retval = PTR_ERR(devname);
+		return -EFAULT;
+
+	devname = strndup_user(tmp.devname, PATH_MAX);
 	if (IS_ERR(devname))
-		goto out;
-	retval = do_mount(devname->name, dirname, "iso9660", flags, NULL);
-	putname(devname);
- out:
-	return retval;
+		return PTR_ERR(devname);
+
+	return do_mount(devname, dirname, "iso9660", flags, NULL);
 }
 
 static int