[PATCH 22/24] btrfs/acl: handle idmapped mounts

[Christian Brauner <brauner@kernel.org>]

From: Christian Brauner <christian.brauner@ubuntu.com>

Make the btrfs acl code idmapped mount aware. The posix default and posix
access acls are the only acls other than some specific xattrs that take dac
permissions into account. On an idmapped mount they need to be translated
according to the mount's userns. The main change is done to __btrfs_set_acl()
which is responsible for translating posix acls to their final on-disk
representation. The btrfs_init_acl() helper does not need to take the idmapped
mount into account since it is called in the context of file creation
operations (mknod, create, mkdir, symlink, tmpfile) and is used for
btrfs_init_inode_security() to copy posix default and posix access permissions
from the parent directory. These acls need to be inherited unmodified from the
parent directory. This is identical to what we do for ext4 and xfs.

Cc: Chris Mason <clm@fb.com>
Cc: Josef Bacik <josef@toxicpanda.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: David Sterba <dsterba@suse.com>
Cc: linux-btrfs@vger.kernel.org
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
---
 fs/btrfs/acl.c | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/fs/btrfs/acl.c b/fs/btrfs/acl.c
index d95eb5c8cb37..3ebf415e5211 100644
--- a/fs/btrfs/acl.c
+++ b/fs/btrfs/acl.c
@@ -53,7 +53,8 @@ struct posix_acl *btrfs_get_acl(struct inode *inode, int type)
 }
 
 static int __btrfs_set_acl(struct btrfs_trans_handle *trans,
-			 struct inode *inode, struct posix_acl *acl, int type)
+			   struct user_namespace *mnt_userns,
+			   struct inode *inode, struct posix_acl *acl, int type)
 {
 	int ret, size = 0;
 	const char *name;
@@ -88,7 +89,7 @@ static int __btrfs_set_acl(struct btrfs_trans_handle *trans,
 			goto out;
 		}
 
-		ret = posix_acl_to_xattr(&init_user_ns, acl, value, size);
+		ret = posix_acl_to_xattr(mnt_userns, acl, value, size);
 		if (ret < 0)
 			goto out;
 	}
@@ -114,12 +115,12 @@ int btrfs_set_acl(struct user_namespace *mnt_userns, struct inode *inode,
 	umode_t old_mode = inode->i_mode;
 
 	if (type == ACL_TYPE_ACCESS && acl) {
-		ret = posix_acl_update_mode(&init_user_ns, inode,
+		ret = posix_acl_update_mode(mnt_userns, inode,
 					    &inode->i_mode, &acl);
 		if (ret)
 			return ret;
 	}
-	ret = __btrfs_set_acl(NULL, inode, acl, type);
+	ret = __btrfs_set_acl(NULL, mnt_userns, inode, acl, type);
 	if (ret)
 		inode->i_mode = old_mode;
 	return ret;
@@ -140,14 +141,14 @@ int btrfs_init_acl(struct btrfs_trans_handle *trans,
 		return ret;
 
 	if (default_acl) {
-		ret = __btrfs_set_acl(trans, inode, default_acl,
+		ret = __btrfs_set_acl(trans, &init_user_ns, inode, default_acl,
 				      ACL_TYPE_DEFAULT);
 		posix_acl_release(default_acl);
 	}
 
 	if (acl) {
 		if (!ret)
-			ret = __btrfs_set_acl(trans, inode, acl,
+			ret = __btrfs_set_acl(trans, &init_user_ns, inode, acl,
 					      ACL_TYPE_ACCESS);
 		posix_acl_release(acl);
 	}
-- 
2.30.2