fs: make helpers idmap mount aware

Extend some inode methods with an additional user namespace argument. A
filesystem that is aware of idmapped mounts will receive the user
namespace the mount has been marked with. This can be used for
additional permission checking and also to enable filesystems to
translate between uids and gids if they need to. We have implemented all
relevant helpers in earlier patches.

As requested we simply extend the exisiting inode method instead of
introducing new ones. This is a little more code churn but it's mostly
mechanical and doesnt't leave us with additional inode methods.

Link: https://lore.kernel.org/r/20210121131959.646623-25-christian.brauner@ubuntu.com
Cc: Christoph Hellwig <hch@lst.de>
Cc: David Howells <dhowells@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: linux-fsdevel@vger.kernel.org
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>

1 files changed, 21 insertions, 16 deletions

diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c
index d2e318ed9b26..06a18700a845 100644
--- a/fs/fuse/dir.c
+++ b/fs/fuse/dir.c
@@ -605,7 +605,8 @@ out_err:
 	return err;
 }
 
-static int fuse_mknod(struct inode *, struct dentry *, umode_t, dev_t);
+static int fuse_mknod(struct user_namespace *, struct inode *, struct dentry *,
+		      umode_t, dev_t);
 static int fuse_atomic_open(struct inode *dir, struct dentry *entry,
 			    struct file *file, unsigned flags,
 			    umode_t mode)
@@ -645,7 +646,7 @@ out_dput:
 	return err;
 
 mknod:
-	err = fuse_mknod(dir, entry, mode, 0);
+	err = fuse_mknod(&init_user_ns, dir, entry, mode, 0);
 	if (err)
 		goto out_dput;
 no_open:
@@ -715,8 +716,8 @@ static int create_new_entry(struct fuse_mount *fm, struct fuse_args *args,
 	return err;
 }
 
-static int fuse_mknod(struct inode *dir, struct dentry *entry, umode_t mode,
-		      dev_t rdev)
+static int fuse_mknod(struct user_namespace *mnt_userns, struct inode *dir,
+		      struct dentry *entry, umode_t mode, dev_t rdev)
 {
 	struct fuse_mknod_in inarg;
 	struct fuse_mount *fm = get_fuse_mount(dir);
@@ -738,13 +739,14 @@ static int fuse_mknod(struct inode *dir, struct dentry *entry, umode_t mode,
 	return create_new_entry(fm, &args, dir, entry, mode);
 }
 
-static int fuse_create(struct inode *dir, struct dentry *entry, umode_t mode,
-		       bool excl)
+static int fuse_create(struct user_namespace *mnt_userns, struct inode *dir,
+		       struct dentry *entry, umode_t mode, bool excl)
 {
-	return fuse_mknod(dir, entry, mode, 0);
+	return fuse_mknod(&init_user_ns, dir, entry, mode, 0);
 }
 
-static int fuse_mkdir(struct inode *dir, struct dentry *entry, umode_t mode)
+static int fuse_mkdir(struct user_namespace *mnt_userns, struct inode *dir,
+		      struct dentry *entry, umode_t mode)
 {
 	struct fuse_mkdir_in inarg;
 	struct fuse_mount *fm = get_fuse_mount(dir);
@@ -765,8 +767,8 @@ static int fuse_mkdir(struct inode *dir, struct dentry *entry, umode_t mode)
 	return create_new_entry(fm, &args, dir, entry, S_IFDIR);
 }
 
-static int fuse_symlink(struct inode *dir, struct dentry *entry,
-			const char *link)
+static int fuse_symlink(struct user_namespace *mnt_userns, struct inode *dir,
+			struct dentry *entry, const char *link)
 {
 	struct fuse_mount *fm = get_fuse_mount(dir);
 	unsigned len = strlen(link) + 1;
@@ -908,9 +910,9 @@ static int fuse_rename_common(struct inode *olddir, struct dentry *oldent,
 	return err;
 }
 
-static int fuse_rename2(struct inode *olddir, struct dentry *oldent,
-			struct inode *newdir, struct dentry *newent,
-			unsigned int flags)
+static int fuse_rename2(struct user_namespace *mnt_userns, struct inode *olddir,
+			struct dentry *oldent, struct inode *newdir,
+			struct dentry *newent, unsigned int flags)
 {
 	struct fuse_conn *fc = get_fuse_conn(olddir);
 	int err;
@@ -1249,7 +1251,8 @@ static int fuse_perm_getattr(struct inode *inode, int mask)
  * access request is sent.  Execute permission is still checked
  * locally based on file mode.
  */
-static int fuse_permission(struct inode *inode, int mask)
+static int fuse_permission(struct user_namespace *mnt_userns,
+			   struct inode *inode, int mask)
 {
 	struct fuse_conn *fc = get_fuse_conn(inode);
 	bool refreshed = false;
@@ -1757,7 +1760,8 @@ error:
 	return err;
 }
 
-static int fuse_setattr(struct dentry *entry, struct iattr *attr)
+static int fuse_setattr(struct user_namespace *mnt_userns, struct dentry *entry,
+			struct iattr *attr)
 {
 	struct inode *inode = d_inode(entry);
 	struct fuse_conn *fc = get_fuse_conn(inode);
@@ -1819,7 +1823,8 @@ static int fuse_setattr(struct dentry *entry, struct iattr *attr)
 	return ret;
 }
 
-static int fuse_getattr(const struct path *path, struct kstat *stat,
+static int fuse_getattr(struct user_namespace *mnt_userns,
+			const struct path *path, struct kstat *stat,
 			u32 request_mask, unsigned int flags)
 {
 	struct inode *inode = d_inode(path->dentry);