Pass in the struct filename pointers instead of the user string, and
update the three callers to do the same. This is heavily based on
commit dbea8d345177 ("fs: make do_renameat2() take struct filename").

This behaves like do_unlinkat() and do_renameat2().

Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Dmitry Kadashev <redacted>
---
 fs/internal.h |  1 +
 fs/namei.c    | 25 +++++++++++++++++++------
 2 files changed, 20 insertions(+), 6 deletions(-)

diff --git a/fs/internal.h b/fs/internal.h
index c6c85f6ad598..b10005dfaa48 100644
--- a/fs/internal.h
+++ b/fs/internal.h

@@ -76,6 +76,7 @@ long do_unlinkat(int dfd, struct filename *name);
 int may_linkat(struct path *link);
 int do_renameat2(int olddfd, struct filename *oldname, int newdfd,
                 struct filename *newname, unsigned int flags);
+long do_mkdirat(int dfd, struct filename *name, umode_t mode);

 /*
  * namespace.c

diff --git a/fs/namei.c b/fs/namei.c
index 4cae88733a5c..3657bdf1aafc 100644
--- a/fs/namei.c
+++ b/fs/namei.c

@@ -3431,7 +3431,7 @@ struct file *do_file_open_root(struct dentry *dentry, struct vfsmount *mnt,
        return file;
 }

-static struct dentry *filename_create(int dfd, struct filename *name,
+static struct dentry *__filename_create(int dfd, struct filename *name,
                                struct path *path, unsigned int lookup_flags)
 {
        struct dentry *dentry = ERR_PTR(-EEXIST);

@@ -3487,7 +3487,6 @@ static struct dentry *filename_create(int dfd, struct filename *name,
                error = err2;
                goto fail;
        }
-       putname(name);
        return dentry;
 fail:
        dput(dentry);

@@ -3502,6 +3501,16 @@ static struct dentry *filename_create(int dfd, struct filename *name,
        return dentry;
 }

+static inline struct dentry *filename_create(int dfd, struct filename *name,
+                               struct path *path, unsigned int lookup_flags)
+{
+       struct dentry *res = __filename_create(dfd, name, path, lookup_flags);
+
+       if (!IS_ERR(res))
+               putname(name);
+       return res;
+}
+
 struct dentry *kern_path_create(int dfd, const char *pathname,
                                struct path *path, unsigned int lookup_flags)
 {

@@ -3654,15 +3663,18 @@ int vfs_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
 }
 EXPORT_SYMBOL(vfs_mkdir);

-static long do_mkdirat(int dfd, const char __user *pathname, umode_t mode)
+long do_mkdirat(int dfd, struct filename *name, umode_t mode)
 {
        struct dentry *dentry;
        struct path path;
        int error;
        unsigned int lookup_flags = LOOKUP_DIRECTORY;

+       if (IS_ERR(name))
+               return PTR_ERR(name);
+
 retry:
-       dentry = user_path_create(dfd, pathname, &path, lookup_flags);
+       dentry = __filename_create(dfd, name, &path, lookup_flags);
        if (IS_ERR(dentry))
                return PTR_ERR(dentry);

@@ -3676,17 +3688,18 @@ static long do_mkdirat(int dfd, const char __user *pathname, umode_t mode)
                lookup_flags |= LOOKUP_REVAL;
                goto retry;
        }
+       putname(name);
        return error;
 }

 SYSCALL_DEFINE3(mkdirat, int, dfd, const char __user *, pathname, umode_t, mode)
 {
-       return do_mkdirat(dfd, pathname, mode);
+       return do_mkdirat(dfd, getname(pathname), mode);
 }

 SYSCALL_DEFINE2(mkdir, const char __user *, pathname, umode_t, mode)
 {
-       return do_mkdirat(AT_FDCWD, pathname, mode);
+       return do_mkdirat(AT_FDCWD, getname(pathname), mode);
 }

 int vfs_rmdir(struct inode *dir, struct dentry *dentry)
--

2.30.0