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, 25 insertions, 14 deletions

diff --git a/mm/shmem.c b/mm/shmem.c
index 339d5530d3a9..facdd1a9c524 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1060,7 +1060,8 @@ void shmem_truncate_range(struct inode *inode, loff_t lstart, loff_t lend)
 }
 EXPORT_SYMBOL_GPL(shmem_truncate_range);
 
-static int shmem_getattr(const struct path *path, struct kstat *stat,
+static int shmem_getattr(struct user_namespace *mnt_userns,
+			 const struct path *path, struct kstat *stat,
 			 u32 request_mask, unsigned int query_flags)
 {
 	struct inode *inode = path->dentry->d_inode;
@@ -1080,7 +1081,8 @@ static int shmem_getattr(const struct path *path, struct kstat *stat,
 	return 0;
 }
 
-static int shmem_setattr(struct dentry *dentry, struct iattr *attr)
+static int shmem_setattr(struct user_namespace *mnt_userns,
+			 struct dentry *dentry, struct iattr *attr)
 {
 	struct inode *inode = d_inode(dentry);
 	struct shmem_inode_info *info = SHMEM_I(inode);
@@ -2917,7 +2919,8 @@ static int shmem_statfs(struct dentry *dentry, struct kstatfs *buf)
  * File creation. Allocate an inode, and we're done..
  */
 static int
-shmem_mknod(struct inode *dir, struct dentry *dentry, umode_t mode, dev_t dev)
+shmem_mknod(struct user_namespace *mnt_userns, struct inode *dir,
+	    struct dentry *dentry, umode_t mode, dev_t dev)
 {
 	struct inode *inode;
 	int error = -ENOSPC;
@@ -2946,7 +2949,8 @@ out_iput:
 }
 
 static int
-shmem_tmpfile(struct inode *dir, struct dentry *dentry, umode_t mode)
+shmem_tmpfile(struct user_namespace *mnt_userns, struct inode *dir,
+	      struct dentry *dentry, umode_t mode)
 {
 	struct inode *inode;
 	int error = -ENOSPC;
@@ -2969,20 +2973,22 @@ out_iput:
 	return error;
 }
 
-static int shmem_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
+static int shmem_mkdir(struct user_namespace *mnt_userns, struct inode *dir,
+		       struct dentry *dentry, umode_t mode)
 {
 	int error;
 
-	if ((error = shmem_mknod(dir, dentry, mode | S_IFDIR, 0)))
+	if ((error = shmem_mknod(&init_user_ns, dir, dentry,
+				 mode | S_IFDIR, 0)))
 		return error;
 	inc_nlink(dir);
 	return 0;
 }
 
-static int shmem_create(struct inode *dir, struct dentry *dentry, umode_t mode,
-		bool excl)
+static int shmem_create(struct user_namespace *mnt_userns, struct inode *dir,
+			struct dentry *dentry, umode_t mode, bool excl)
 {
-	return shmem_mknod(dir, dentry, mode | S_IFREG, 0);
+	return shmem_mknod(&init_user_ns, dir, dentry, mode | S_IFREG, 0);
 }
 
 /*
@@ -3062,7 +3068,8 @@ static int shmem_exchange(struct inode *old_dir, struct dentry *old_dentry, stru
 	return 0;
 }
 
-static int shmem_whiteout(struct inode *old_dir, struct dentry *old_dentry)
+static int shmem_whiteout(struct user_namespace *mnt_userns,
+			  struct inode *old_dir, struct dentry *old_dentry)
 {
 	struct dentry *whiteout;
 	int error;
@@ -3071,7 +3078,7 @@ static int shmem_whiteout(struct inode *old_dir, struct dentry *old_dentry)
 	if (!whiteout)
 		return -ENOMEM;
 
-	error = shmem_mknod(old_dir, whiteout,
+	error = shmem_mknod(&init_user_ns, old_dir, whiteout,
 			    S_IFCHR | WHITEOUT_MODE, WHITEOUT_DEV);
 	dput(whiteout);
 	if (error)
@@ -3094,7 +3101,10 @@ static int shmem_whiteout(struct inode *old_dir, struct dentry *old_dentry)
  * it exists so that the VFS layer correctly free's it when it
  * gets overwritten.
  */
-static int shmem_rename2(struct inode *old_dir, struct dentry *old_dentry, struct inode *new_dir, struct dentry *new_dentry, unsigned int flags)
+static int shmem_rename2(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 inode *inode = d_inode(old_dentry);
 	int they_are_dirs = S_ISDIR(inode->i_mode);
@@ -3111,7 +3121,7 @@ static int shmem_rename2(struct inode *old_dir, struct dentry *old_dentry, struc
 	if (flags & RENAME_WHITEOUT) {
 		int error;
 
-		error = shmem_whiteout(old_dir, old_dentry);
+		error = shmem_whiteout(&init_user_ns, old_dir, old_dentry);
 		if (error)
 			return error;
 	}
@@ -3135,7 +3145,8 @@ static int shmem_rename2(struct inode *old_dir, struct dentry *old_dentry, struc
 	return 0;
 }
 
-static int shmem_symlink(struct inode *dir, struct dentry *dentry, const char *symname)
+static int shmem_symlink(struct user_namespace *mnt_userns, struct inode *dir,
+			 struct dentry *dentry, const char *symname)
 {
 	int error;
 	int len;