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>

4 files changed, 24 insertions, 19 deletions

diff --git a/fs/overlayfs/dir.c b/fs/overlayfs/dir.c
index 6904cc2ed7bb..8b3be7342a8c 100644
--- a/fs/overlayfs/dir.c
+++ b/fs/overlayfs/dir.c
@@ -650,19 +650,20 @@ out:
 	return err;
 }
 
-static int ovl_create(struct inode *dir, struct dentry *dentry, umode_t mode,
-		      bool excl)
+static int ovl_create(struct user_namespace *mnt_userns, struct inode *dir,
+		      struct dentry *dentry, umode_t mode, bool excl)
 {
 	return ovl_create_object(dentry, (mode & 07777) | S_IFREG, 0, NULL);
 }
 
-static int ovl_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
+static int ovl_mkdir(struct user_namespace *mnt_userns, struct inode *dir,
+		     struct dentry *dentry, umode_t mode)
 {
 	return ovl_create_object(dentry, (mode & 07777) | S_IFDIR, 0, NULL);
 }
 
-static int ovl_mknod(struct inode *dir, struct dentry *dentry, umode_t mode,
-		     dev_t rdev)
+static int ovl_mknod(struct user_namespace *mnt_userns, struct inode *dir,
+		     struct dentry *dentry, umode_t mode, dev_t rdev)
 {
 	/* Don't allow creation of "whiteout" on overlay */
 	if (S_ISCHR(mode) && rdev == WHITEOUT_DEV)
@@ -671,8 +672,8 @@ static int ovl_mknod(struct inode *dir, struct dentry *dentry, umode_t mode,
 	return ovl_create_object(dentry, mode, rdev, NULL);
 }
 
-static int ovl_symlink(struct inode *dir, struct dentry *dentry,
-		       const char *link)
+static int ovl_symlink(struct user_namespace *mnt_userns, struct inode *dir,
+		       struct dentry *dentry, const char *link)
 {
 	return ovl_create_object(dentry, S_IFLNK, 0, link);
 }
@@ -1069,9 +1070,9 @@ static int ovl_set_redirect(struct dentry *dentry, bool samedir)
 	return err;
 }
 
-static int ovl_rename(struct inode *olddir, struct dentry *old,
-		      struct inode *newdir, struct dentry *new,
-		      unsigned int flags)
+static int ovl_rename(struct user_namespace *mnt_userns, struct inode *olddir,
+		      struct dentry *old, struct inode *newdir,
+		      struct dentry *new, unsigned int flags)
 {
 	int err;
 	struct dentry *old_upperdir;
diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
index 023fde466e3a..e78d45dfeaee 100644
--- a/fs/overlayfs/inode.c
+++ b/fs/overlayfs/inode.c
@@ -14,7 +14,8 @@
 #include "overlayfs.h"
 
 
-int ovl_setattr(struct dentry *dentry, struct iattr *attr)
+int ovl_setattr(struct user_namespace *mnt_userns, struct dentry *dentry,
+		struct iattr *attr)
 {
 	int err;
 	bool full_copy_up = false;
@@ -154,8 +155,8 @@ static int ovl_map_dev_ino(struct dentry *dentry, struct kstat *stat, int fsid)
 	return 0;
 }
 
-int ovl_getattr(const struct path *path, struct kstat *stat,
-		u32 request_mask, unsigned int flags)
+int ovl_getattr(struct user_namespace *mnt_userns, const struct path *path,
+		struct kstat *stat, u32 request_mask, unsigned int flags)
 {
 	struct dentry *dentry = path->dentry;
 	enum ovl_path_type type;
@@ -277,7 +278,8 @@ out:
 	return err;
 }
 
-int ovl_permission(struct inode *inode, int mask)
+int ovl_permission(struct user_namespace *mnt_userns,
+		   struct inode *inode, int mask)
 {
 	struct inode *upperinode = ovl_inode_upper(inode);
 	struct inode *realinode = upperinode ?: ovl_inode_lower(inode);
diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h
index 5e9eb46e741a..78b9d93a33c9 100644
--- a/fs/overlayfs/overlayfs.h
+++ b/fs/overlayfs/overlayfs.h
@@ -444,10 +444,12 @@ int ovl_set_nlink_lower(struct dentry *dentry);
 unsigned int ovl_get_nlink(struct ovl_fs *ofs, struct dentry *lowerdentry,
 			   struct dentry *upperdentry,
 			   unsigned int fallback);
-int ovl_setattr(struct dentry *dentry, struct iattr *attr);
-int ovl_getattr(const struct path *path, struct kstat *stat,
-		u32 request_mask, unsigned int flags);
-int ovl_permission(struct inode *inode, int mask);
+int ovl_setattr(struct user_namespace *mnt_userns, struct dentry *dentry,
+		struct iattr *attr);
+int ovl_getattr(struct user_namespace *mnt_userns, const struct path *path,
+		struct kstat *stat, u32 request_mask, unsigned int flags);
+int ovl_permission(struct user_namespace *mnt_userns, struct inode *inode,
+		   int mask);
 int ovl_xattr_set(struct dentry *dentry, struct inode *inode, const char *name,
 		  const void *value, size_t size, int flags);
 int ovl_xattr_get(struct dentry *dentry, struct inode *inode, const char *name,
diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index 8168ab2dda11..c04612b19054 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -1023,7 +1023,7 @@ ovl_posix_acl_xattr_set(const struct xattr_handler *handler,
 	    !capable_wrt_inode_uidgid(&init_user_ns, inode, CAP_FSETID)) {
 		struct iattr iattr = { .ia_valid = ATTR_KILL_SGID };
 
-		err = ovl_setattr(dentry, &iattr);
+		err = ovl_setattr(&init_user_ns, dentry, &iattr);
 		if (err)
 			return err;
 	}