acl: handle idmapped mounts

The posix acl permission checking helpers determine whether a caller is
privileged over an inode according to the acls associated with the
inode. Add helpers that make it possible to handle acls on idmapped
mounts.

The vfs and the filesystems targeted by this first iteration make use of
posix_acl_fix_xattr_from_user() and posix_acl_fix_xattr_to_user() to
translate basic posix access and default permissions such as the
ACL_USER and ACL_GROUP type according to the initial user namespace (or
the superblock's user namespace) to and from the caller's current user
namespace. Adapt these two helpers to handle idmapped mounts whereby we
either map from or into the mount's user namespace depending on in which
direction we're translating.
Similarly, cap_convert_nscap() is used by the vfs to translate user
namespace and non-user namespace aware filesystem capabilities from the
superblock's user namespace to the caller's user namespace. Enable it to
handle idmapped mounts by accounting for the mount's user namespace.

In addition the fileystems targeted in the first iteration of this patch
series make use of the posix_acl_chmod() and, posix_acl_update_mode()
helpers. Both helpers perform permission checks on the target inode. Let
them handle idmapped mounts. These two helpers are called when posix
acls are set by the respective filesystems to handle this case we extend
the ->set() method to take an additional user namespace argument to pass
the mount's user namespace down.

Link: https://lore.kernel.org/r/20210121131959.646623-9-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>

63 files changed, 172 insertions, 64 deletions

diff --git a/fs/9p/acl.c b/fs/9p/acl.c
index d77b28e8d57a..1c14f18a6ec9 100644
--- a/fs/9p/acl.c
+++ b/fs/9p/acl.c
@@ -239,6 +239,7 @@ static int v9fs_xattr_get_acl(const struct xattr_handler *handler,
 }
 
 static int v9fs_xattr_set_acl(const struct xattr_handler *handler,
+			      struct user_namespace *mnt_userns,
 			      struct dentry *dentry, struct inode *inode,
 			      const char *name, const void *value,
 			      size_t size, int flags)
@@ -279,7 +280,8 @@ static int v9fs_xattr_set_acl(const struct xattr_handler *handler,
 			struct iattr iattr = { 0 };
 			struct posix_acl *old_acl = acl;
 
-			retval = posix_acl_update_mode(inode, &iattr.ia_mode, &acl);
+			retval = posix_acl_update_mode(mnt_userns, inode,
+						       &iattr.ia_mode, &acl);
 			if (retval)
 				goto err_out;
 			if (!acl) {
diff --git a/fs/9p/xattr.c b/fs/9p/xattr.c
index 87217dd0433e..ee331845e2c7 100644
--- a/fs/9p/xattr.c
+++ b/fs/9p/xattr.c
@@ -157,6 +157,7 @@ static int v9fs_xattr_handler_get(const struct xattr_handler *handler,
 }
 
 static int v9fs_xattr_handler_set(const struct xattr_handler *handler,
+				  struct user_namespace *mnt_userns,
 				  struct dentry *dentry, struct inode *inode,
 				  const char *name, const void *value,
 				  size_t size, int flags)
diff --git a/fs/afs/xattr.c b/fs/afs/xattr.c
index 95c573dcda11..c629caae5002 100644
--- a/fs/afs/xattr.c
+++ b/fs/afs/xattr.c
@@ -120,6 +120,7 @@ static const struct afs_operation_ops afs_store_acl_operation = {
  * Set a file's AFS3 ACL.
  */
 static int afs_xattr_set_acl(const struct xattr_handler *handler,
+			     struct user_namespace *mnt_userns,
                              struct dentry *dentry,
                              struct inode *inode, const char *name,
                              const void *buffer, size_t size, int flags)
@@ -248,6 +249,7 @@ static const struct afs_operation_ops yfs_store_opaque_acl2_operation = {
  * Set a file's YFS ACL.
  */
 static int afs_xattr_set_yfs(const struct xattr_handler *handler,
+			     struct user_namespace *mnt_userns,
                              struct dentry *dentry,
                              struct inode *inode, const char *name,
                              const void *buffer, size_t size, int flags)
diff --git a/fs/btrfs/acl.c b/fs/btrfs/acl.c
index a0af1b952c4d..d12a5a8730a8 100644
--- a/fs/btrfs/acl.c
+++ b/fs/btrfs/acl.c
@@ -113,7 +113,8 @@ int btrfs_set_acl(struct inode *inode, struct posix_acl *acl, int type)
 	umode_t old_mode = inode->i_mode;
 
 	if (type == ACL_TYPE_ACCESS && acl) {
-		ret = posix_acl_update_mode(inode, &inode->i_mode, &acl);
+		ret = posix_acl_update_mode(&init_user_ns, inode,
+					    &inode->i_mode, &acl);
 		if (ret)
 			return ret;
 	}
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 792191a8705b..6c18fb1a25af 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -5070,7 +5070,8 @@ static int btrfs_setattr(struct dentry *dentry, struct iattr *attr)
 		err = btrfs_dirty_inode(inode);
 
 		if (!err && attr->ia_valid & ATTR_MODE)
-			err = posix_acl_chmod(inode, inode->i_mode);
+			err = posix_acl_chmod(&init_user_ns, inode,
+					      inode->i_mode);
 	}
 
 	return err;
diff --git a/fs/btrfs/xattr.c b/fs/btrfs/xattr.c
index af6246f36a9e..b025102e435f 100644
--- a/fs/btrfs/xattr.c
+++ b/fs/btrfs/xattr.c
@@ -362,6 +362,7 @@ static int btrfs_xattr_handler_get(const struct xattr_handler *handler,
 }
 
 static int btrfs_xattr_handler_set(const struct xattr_handler *handler,
+				   struct user_namespace *mnt_userns,
 				   struct dentry *unused, struct inode *inode,
 				   const char *name, const void *buffer,
 				   size_t size, int flags)
@@ -371,6 +372,7 @@ static int btrfs_xattr_handler_set(const struct xattr_handler *handler,
 }
 
 static int btrfs_xattr_handler_set_prop(const struct xattr_handler *handler,
+					struct user_namespace *mnt_userns,
 					struct dentry *unused, struct inode *inode,
 					const char *name, const void *value,
 					size_t size, int flags)
diff --git a/fs/ceph/acl.c b/fs/ceph/acl.c
index e0465741c591..52a01ddbc4ac 100644
--- a/fs/ceph/acl.c
+++ b/fs/ceph/acl.c
@@ -100,7 +100,8 @@ int ceph_set_acl(struct inode *inode, struct posix_acl *acl, int type)
 	case ACL_TYPE_ACCESS:
 		name = XATTR_NAME_POSIX_ACL_ACCESS;
 		if (acl) {
-			ret = posix_acl_update_mode(inode, &new_mode, &acl);
+			ret = posix_acl_update_mode(&init_user_ns, inode,
+						    &new_mode, &acl);
 			if (ret)
 				goto out;
 		}
diff --git a/fs/ceph/inode.c b/fs/ceph/inode.c
index 285d3baca27e..145e26a4ddbb 100644
--- a/fs/ceph/inode.c
+++ b/fs/ceph/inode.c
@@ -2262,7 +2262,7 @@ int ceph_setattr(struct dentry *dentry, struct iattr *attr)
 	err = __ceph_setattr(inode, attr);
 
 	if (err >= 0 && (attr->ia_valid & ATTR_MODE))
-		err = posix_acl_chmod(inode, attr->ia_mode);
+		err = posix_acl_chmod(&init_user_ns, inode, attr->ia_mode);
 
 	return err;
 }
diff --git a/fs/ceph/xattr.c b/fs/ceph/xattr.c
index 24997982de01..02f59bcb4f27 100644
--- a/fs/ceph/xattr.c
+++ b/fs/ceph/xattr.c
@@ -1238,6 +1238,7 @@ static int ceph_get_xattr_handler(const struct xattr_handler *handler,
 }
 
 static int ceph_set_xattr_handler(const struct xattr_handler *handler,
+				  struct user_namespace *mnt_userns,
 				  struct dentry *unused, struct inode *inode,
 				  const char *name, const void *value,
 				  size_t size, int flags)
diff --git a/fs/cifs/xattr.c b/fs/cifs/xattr.c
index 6b658a1172ef..41a611e76bb7 100644
--- a/fs/cifs/xattr.c
+++ b/fs/cifs/xattr.c
@@ -101,6 +101,7 @@ static int cifs_creation_time_set(unsigned int xid, struct cifs_tcon *pTcon,
 }
 
 static int cifs_xattr_set(const struct xattr_handler *handler,
+			  struct user_namespace *mnt_userns,
 			  struct dentry *dentry, struct inode *inode,
 			  const char *name, const void *value,
 			  size_t size, int flags)
diff --git a/fs/ecryptfs/inode.c b/fs/ecryptfs/inode.c
index d3ea0c57b075..ac6472a82567 100644
--- a/fs/ecryptfs/inode.c
+++ b/fs/ecryptfs/inode.c
@@ -1133,6 +1133,7 @@ static int ecryptfs_xattr_get(const struct xattr_handler *handler,
 }
 
 static int ecryptfs_xattr_set(const struct xattr_handler *handler,
+			      struct user_namespace *mnt_userns,
 			      struct dentry *dentry, struct inode *inode,
 			      const char *name, const void *value, size_t size,
 			      int flags)
diff --git a/fs/ext2/acl.c b/fs/ext2/acl.c
index cf4c77f8dd08..9031f7df2d48 100644
--- a/fs/ext2/acl.c
+++ b/fs/ext2/acl.c
@@ -223,7 +223,8 @@ ext2_set_acl(struct inode *inode, struct posix_acl *acl, int type)
 	umode_t mode = inode->i_mode;
 
 	if (type == ACL_TYPE_ACCESS && acl) {
-		error = posix_acl_update_mode(inode, &mode, &acl);
+		error = posix_acl_update_mode(&init_user_ns, inode, &mode,
+					      &acl);
 		if (error)
 			return error;
 		update_mode = 1;
diff --git a/fs/ext2/inode.c b/fs/ext2/inode.c
index 06c0cf28c1a0..9de813635d8d 100644
--- a/fs/ext2/inode.c
+++ b/fs/ext2/inode.c
@@ -1691,7 +1691,7 @@ int ext2_setattr(struct dentry *dentry, struct iattr *iattr)
 	}
 	setattr_copy(&init_user_ns, inode, iattr);
 	if (iattr->ia_valid & ATTR_MODE)
-		error = posix_acl_chmod(inode, inode->i_mode);
+		error = posix_acl_chmod(&init_user_ns, inode, inode->i_mode);
 	mark_inode_dirty(inode);
 
 	return error;
diff --git a/fs/ext2/xattr_security.c b/fs/ext2/xattr_security.c
index 9a682e440acb..ebade1f52451 100644
--- a/fs/ext2/xattr_security.c
+++ b/fs/ext2/xattr_security.c
@@ -19,6 +19,7 @@ ext2_xattr_security_get(const struct xattr_handler *handler,
 
 static int
 ext2_xattr_security_set(const struct xattr_handler *handler,
+			struct user_namespace *mnt_userns,
 			struct dentry *unused, struct inode *inode,
 			const char *name, const void *value,
 			size_t size, int flags)
diff --git a/fs/ext2/xattr_trusted.c b/fs/ext2/xattr_trusted.c
index 49add1107850..18a87d5dd1ab 100644
--- a/fs/ext2/xattr_trusted.c
+++ b/fs/ext2/xattr_trusted.c
@@ -26,6 +26,7 @@ ext2_xattr_trusted_get(const struct xattr_handler *handler,
 
 static int
 ext2_xattr_trusted_set(const struct xattr_handler *handler,
+		       struct user_namespace *mnt_userns,
 		       struct dentry *unused, struct inode *inode,
 		       const char *name, const void *value,
 		       size_t size, int flags)
diff --git a/fs/ext2/xattr_user.c b/fs/ext2/xattr_user.c
index c243a3b4d69d..58092449f8ff 100644
--- a/fs/ext2/xattr_user.c
+++ b/fs/ext2/xattr_user.c
@@ -30,6 +30,7 @@ ext2_xattr_user_get(const struct xattr_handler *handler,
 
 static int
 ext2_xattr_user_set(const struct xattr_handler *handler,
+		    struct user_namespace *mnt_userns,
 		    struct dentry *unused, struct inode *inode,
 		    const char *name, const void *value,
 		    size_t size, int flags)
diff --git a/fs/ext4/acl.c b/fs/ext4/acl.c
index 68aaed48315f..7b0fb66bc04d 100644
--- a/fs/ext4/acl.c
+++ b/fs/ext4/acl.c
@@ -245,7 +245,8 @@ retry:
 	ext4_fc_start_update(inode);
 
 	if ((type == ACL_TYPE_ACCESS) && acl) {
-		error = posix_acl_update_mode(inode, &mode, &acl);
+		error = posix_acl_update_mode(&init_user_ns, inode, &mode,
+					      &acl);
 		if (error)
 			goto out_stop;
 		if (mode != inode->i_mode)
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 8edfa3e226e6..24ea5851e90a 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -5524,7 +5524,7 @@ out_mmap_sem:
 		ext4_orphan_del(NULL, inode);
 
 	if (!error && (ia_valid & ATTR_MODE))
-		rc = posix_acl_chmod(inode, inode->i_mode);
+		rc = posix_acl_chmod(&init_user_ns, inode, inode->i_mode);
 
 err_out:
 	if  (error)
diff --git a/fs/ext4/xattr_hurd.c b/fs/ext4/xattr_hurd.c
index 8cfa74a56361..c78df5790377 100644
--- a/fs/ext4/xattr_hurd.c
+++ b/fs/ext4/xattr_hurd.c
@@ -32,6 +32,7 @@ ext4_xattr_hurd_get(const struct xattr_handler *handler,
 
 static int
 ext4_xattr_hurd_set(const struct xattr_handler *handler,
+		    struct user_namespace *mnt_userns,
 		    struct dentry *unused, struct inode *inode,
 		    const char *name, const void *value,
 		    size_t size, int flags)
diff --git a/fs/ext4/xattr_security.c b/fs/ext4/xattr_security.c
index 197a9d8a15ef..8213f66f7b2d 100644
--- a/fs/ext4/xattr_security.c
+++ b/fs/ext4/xattr_security.c
@@ -23,6 +23,7 @@ ext4_xattr_security_get(const struct xattr_handler *handler,
 
 static int
 ext4_xattr_security_set(const struct xattr_handler *handler,
+			struct user_namespace *mnt_userns,
 			struct dentry *unused, struct inode *inode,
 			const char *name, const void *value,
 			size_t size, int flags)
diff --git a/fs/ext4/xattr_trusted.c b/fs/ext4/xattr_trusted.c
index e9389e5d75c3..7c21ffb26d25 100644
--- a/fs/ext4/xattr_trusted.c
+++ b/fs/ext4/xattr_trusted.c
@@ -30,6 +30,7 @@ ext4_xattr_trusted_get(const struct xattr_handler *handler,
 
 static int
 ext4_xattr_trusted_set(const struct xattr_handler *handler,
+		       struct user_namespace *mnt_userns,
 		       struct dentry *unused, struct inode *inode,
 		       const char *name, const void *value,
 		       size_t size, int flags)
diff --git a/fs/ext4/xattr_user.c b/fs/ext4/xattr_user.c
index d4546184b34b..2fe7ff0a479c 100644
--- a/fs/ext4/xattr_user.c
+++ b/fs/ext4/xattr_user.c
@@ -31,6 +31,7 @@ ext4_xattr_user_get(const struct xattr_handler *handler,
 
 static int
 ext4_xattr_user_set(const struct xattr_handler *handler,
+		    struct user_namespace *mnt_userns,
 		    struct dentry *unused, struct inode *inode,
 		    const char *name, const void *value,
 		    size_t size, int flags)
diff --git a/fs/f2fs/acl.c b/fs/f2fs/acl.c
index 1e5e9b1136ee..6a95bf28f602 100644
--- a/fs/f2fs/acl.c
+++ b/fs/f2fs/acl.c
@@ -213,7 +213,8 @@ static int __f2fs_set_acl(struct inode *inode, int type,
 	case ACL_TYPE_ACCESS:
 		name_index = F2FS_XATTR_INDEX_POSIX_ACL_ACCESS;
 		if (acl && !ipage) {
-			error = posix_acl_update_mode(inode, &mode, &acl);
+			error = posix_acl_update_mode(&init_user_ns, inode,
+						      &mode, &acl);
 			if (error)
 				return error;
 			set_acl_inode(inode, mode);
diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index 90d7b89176de..6ccdfe0606d9 100644
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -831,8 +831,8 @@ int f2fs_getattr(const struct path *path, struct kstat *stat,
 }
 
 #ifdef CONFIG_F2FS_FS_POSIX_ACL
-static void __setattr_copy(struct user_namespace *mnt_userns, struct inode *inode,
-			   const struct iattr *attr)
+static void __setattr_copy(struct user_namespace *mnt_userns,
+			   struct inode *inode, const struct iattr *attr)
 {
 	unsigned int ia_valid = attr->ia_valid;
 
@@ -950,7 +950,8 @@ int f2fs_setattr(struct dentry *dentry, struct iattr *attr)
 	__setattr_copy(&init_user_ns, inode, attr);
 
 	if (attr->ia_valid & ATTR_MODE) {
-		err = posix_acl_chmod(inode, f2fs_get_inode_mode(inode));
+		err = posix_acl_chmod(&init_user_ns, inode,
+				      f2fs_get_inode_mode(inode));
 		if (err || is_inode_flag_set(inode, FI_ACL_MODE)) {
 			inode->i_mode = F2FS_I(inode)->i_acl_mode;
 			clear_inode_flag(inode, FI_ACL_MODE);
diff --git a/fs/f2fs/xattr.c b/fs/f2fs/xattr.c
index d772bf13a814..10081bf74324 100644
--- a/fs/f2fs/xattr.c
+++ b/fs/f2fs/xattr.c
@@ -64,6 +64,7 @@ static int f2fs_xattr_generic_get(const struct xattr_handler *handler,
 }
 
 static int f2fs_xattr_generic_set(const struct xattr_handler *handler,
+		struct user_namespace *mnt_userns,
 		struct dentry *unused, struct inode *inode,
 		const char *name, const void *value,
 		size_t size, int flags)
@@ -107,6 +108,7 @@ static int f2fs_xattr_advise_get(const struct xattr_handler *handler,
 }
 
 static int f2fs_xattr_advise_set(const struct xattr_handler *handler,
+		struct user_namespace *mnt_userns,
 		struct dentry *unused, struct inode *inode,
 		const char *name, const void *value,
 		size_t size, int flags)
diff --git a/fs/fuse/xattr.c b/fs/fuse/xattr.c
index cdea18de94f7..1a7d7ace54e1 100644
--- a/fs/fuse/xattr.c
+++ b/fs/fuse/xattr.c
@@ -188,6 +188,7 @@ static int fuse_xattr_get(const struct xattr_handler *handler,
 }
 
 static int fuse_xattr_set(const struct xattr_handler *handler,
+			  struct user_namespace *mnt_userns,
 			  struct dentry *dentry, struct inode *inode,
 			  const char *name, const void *value, size_t size,
 			  int flags)
@@ -214,6 +215,7 @@ static int no_xattr_get(const struct xattr_handler *handler,
 }
 
 static int no_xattr_set(const struct xattr_handler *handler,
+			struct user_namespace *mnt_userns,
 			struct dentry *dentry, struct inode *nodee,
 			const char *name, const void *value,
 			size_t size, int flags)
diff --git a/fs/gfs2/acl.c b/fs/gfs2/acl.c
index 2e939f5fe751..ce88ef29eef0 100644
--- a/fs/gfs2/acl.c
+++ b/fs/gfs2/acl.c
@@ -130,7 +130,7 @@ int gfs2_set_acl(struct inode *inode, struct posix_acl *acl, int type)
 
 	mode = inode->i_mode;
 	if (type == ACL_TYPE_ACCESS && acl) {
-		ret = posix_acl_update_mode(inode, &mode, &acl);
+		ret = posix_acl_update_mode(&init_user_ns, inode, &mode, &acl);
 		if (ret)
 			goto unlock;
 	}
diff --git a/fs/gfs2/inode.c b/fs/gfs2/inode.c
index 59c25181d108..728405d15a05 100644
--- a/fs/gfs2/inode.c
+++ b/fs/gfs2/inode.c
@@ -1993,7 +1993,8 @@ static int gfs2_setattr(struct dentry *dentry, struct iattr *attr)
 	else {
 		error = gfs2_setattr_simple(inode, attr);
 		if (!error && attr->ia_valid & ATTR_MODE)
-			error = posix_acl_chmod(inode, inode->i_mode);
+			error = posix_acl_chmod(&init_user_ns, inode,
+						inode->i_mode);
 	}
 
 error:
diff --git a/fs/gfs2/xattr.c b/fs/gfs2/xattr.c
index 9d7667bc4292..13969a813410 100644
--- a/fs/gfs2/xattr.c
+++ b/fs/gfs2/xattr.c
@@ -1214,6 +1214,7 @@ int __gfs2_xattr_set(struct inode *inode, const char *name,
 }
 
 static int gfs2_xattr_set(const struct xattr_handler *handler,
+			  struct user_namespace *mnt_userns,
 			  struct dentry *unused, struct inode *inode,
 			  const char *name, const void *value,
 			  size_t size, int flags)
diff --git a/fs/hfs/attr.c b/fs/hfs/attr.c
index 74fa62643136..2bd54efaf416 100644
--- a/fs/hfs/attr.c
+++ b/fs/hfs/attr.c
@@ -121,6 +121,7 @@ static int hfs_xattr_get(const struct xattr_handler *handler,
 }
 
 static int hfs_xattr_set(const struct xattr_handler *handler,
+			 struct user_namespace *mnt_userns,
 			 struct dentry *unused, struct inode *inode,
 			 const char *name, const void *value, size_t size,
 			 int flags)
diff --git a/fs/hfsplus/xattr.c b/fs/hfsplus/xattr.c
index bb0b27d88e50..4d169c5a2673 100644
--- a/fs/hfsplus/xattr.c
+++ b/fs/hfsplus/xattr.c
@@ -858,6 +858,7 @@ static int hfsplus_osx_getxattr(const struct xattr_handler *handler,
 }
 
 static int hfsplus_osx_setxattr(const struct xattr_handler *handler,
+				struct user_namespace *mnt_userns,
 				struct dentry *unused, struct inode *inode,
 				const char *name, const void *buffer,
 				size_t size, int flags)
diff --git a/fs/hfsplus/xattr_security.c b/fs/hfsplus/xattr_security.c
index cfbe6a3bfb1e..c1c7a16cbf21 100644
--- a/fs/hfsplus/xattr_security.c
+++ b/fs/hfsplus/xattr_security.c
@@ -23,6 +23,7 @@ static int hfsplus_security_getxattr(const struct xattr_handler *handler,
 }
 
 static int hfsplus_security_setxattr(const struct xattr_handler *handler,
+				     struct user_namespace *mnt_userns,
 				     struct dentry *unused, struct inode *inode,
 				     const char *name, const void *buffer,
 				     size_t size, int flags)
diff --git