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, 22 insertions, 16 deletions

diff --git a/fs/fat/fat.h b/fs/fat/fat.h
index 922a0c6ba46c..02d4d4234956 100644
--- a/fs/fat/fat.h
+++ b/fs/fat/fat.h
@@ -397,9 +397,11 @@ extern long fat_generic_ioctl(struct file *filp, unsigned int cmd,
 			      unsigned long arg);
 extern const struct file_operations fat_file_operations;
 extern const struct inode_operations fat_file_inode_operations;
-extern int fat_setattr(struct dentry *dentry, struct iattr *attr);
+extern int fat_setattr(struct user_namespace *mnt_userns, struct dentry *dentry,
+		       struct iattr *attr);
 extern void fat_truncate_blocks(struct inode *inode, loff_t offset);
-extern int fat_getattr(const struct path *path, struct kstat *stat,
+extern int fat_getattr(struct user_namespace *mnt_userns,
+		       const struct path *path, struct kstat *stat,
 		       u32 request_mask, unsigned int flags);
 extern int fat_file_fsync(struct file *file, loff_t start, loff_t end,
 			  int datasync);
diff --git a/fs/fat/file.c b/fs/fat/file.c
index f7e04f533d31..dd73d1b70c55 100644
--- a/fs/fat/file.c
+++ b/fs/fat/file.c
@@ -95,7 +95,7 @@ static int fat_ioctl_set_attributes(struct file *file, u32 __user *user_attr)
 		goto out_unlock_inode;
 
 	/* This MUST be done before doing anything irreversible... */
-	err = fat_setattr(file->f_path.dentry, &ia);
+	err = fat_setattr(file_mnt_user_ns(file), file->f_path.dentry, &ia);
 	if (err)
 		goto out_unlock_inode;
 
@@ -394,8 +394,8 @@ void fat_truncate_blocks(struct inode *inode, loff_t offset)
 	fat_flush_inodes(inode->i_sb, inode, NULL);
 }
 
-int fat_getattr(const struct path *path, struct kstat *stat,
-		u32 request_mask, unsigned int flags)
+int fat_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);
 	generic_fillattr(&init_user_ns, inode, stat);
@@ -466,7 +466,8 @@ static int fat_allow_set_time(struct msdos_sb_info *sbi, struct inode *inode)
 /* valid file mode bits */
 #define FAT_VALID_MODE	(S_IFREG | S_IFDIR | S_IRWXUGO)
 
-int fat_setattr(struct dentry *dentry, struct iattr *attr)
+int fat_setattr(struct user_namespace *mnt_userns, struct dentry *dentry,
+		struct iattr *attr)
 {
 	struct msdos_sb_info *sbi = MSDOS_SB(dentry->d_sb);
 	struct inode *inode = d_inode(dentry);
diff --git a/fs/fat/namei_msdos.c b/fs/fat/namei_msdos.c
index 9d062886fbc1..a8f3375d9d10 100644
--- a/fs/fat/namei_msdos.c
+++ b/fs/fat/namei_msdos.c
@@ -261,8 +261,8 @@ static int msdos_add_entry(struct inode *dir, const unsigned char *name,
 }
 
 /***** Create a file */
-static int msdos_create(struct inode *dir, struct dentry *dentry, umode_t mode,
-			bool excl)
+static int msdos_create(struct user_namespace *mnt_userns, struct inode *dir,
+			struct dentry *dentry, umode_t mode, bool excl)
 {
 	struct super_block *sb = dir->i_sb;
 	struct inode *inode = NULL;
@@ -339,7 +339,8 @@ out:
 }
 
 /***** Make a directory */
-static int msdos_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
+static int msdos_mkdir(struct user_namespace *mnt_userns, struct inode *dir,
+		       struct dentry *dentry, umode_t mode)
 {
 	struct super_block *sb = dir->i_sb;
 	struct fat_slot_info sinfo;
@@ -593,7 +594,8 @@ error_inode:
 }
 
 /***** Rename, a wrapper for rename_same_dir & rename_diff_dir */
-static int msdos_rename(struct inode *old_dir, struct dentry *old_dentry,
+static int msdos_rename(struct user_namespace *mnt_userns,
+			struct inode *old_dir, struct dentry *old_dentry,
 			struct inode *new_dir, struct dentry *new_dentry,
 			unsigned int flags)
 {
diff --git a/fs/fat/namei_vfat.c b/fs/fat/namei_vfat.c
index 0cdd0fb9f742..23936ecf79a5 100644
--- a/fs/fat/namei_vfat.c
+++ b/fs/fat/namei_vfat.c
@@ -756,8 +756,8 @@ error:
 	return ERR_PTR(err);
 }
 
-static int vfat_create(struct inode *dir, struct dentry *dentry, umode_t mode,
-		       bool excl)
+static int vfat_create(struct user_namespace *mnt_userns, struct inode *dir,
+		       struct dentry *dentry, umode_t mode, bool excl)
 {
 	struct super_block *sb = dir->i_sb;
 	struct inode *inode;
@@ -846,7 +846,8 @@ out:
 	return err;
 }
 
-static int vfat_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
+static int vfat_mkdir(struct user_namespace *mnt_userns, struct inode *dir,
+		      struct dentry *dentry, umode_t mode)
 {
 	struct super_block *sb = dir->i_sb;
 	struct inode *inode;
@@ -892,9 +893,9 @@ out:
 	return err;
 }
 
-static int vfat_rename(struct inode *old_dir, struct dentry *old_dentry,
-		       struct inode *new_dir, struct dentry *new_dentry,
-		       unsigned int flags)
+static int vfat_rename(struct user_namespace *mnt_userns, struct inode *old_dir,
+		       struct dentry *old_dentry, struct inode *new_dir,
+		       struct dentry *new_dentry, unsigned int flags)
 {
 	struct buffer_head *dotdot_bh;
 	struct msdos_dir_entry *dotdot_de;