[PATCH 17/18] ovl: handle idmappings in ovl_xattr_{g,s}et()

[Christian Brauner <brauner@kernel.org>]

When retrieving xattrs from the upper or lower layers take the relevant
mount's idmapping into account. We rely on the previously introduced
ovl_i_path_real() helper to retrieve the relevant path. This is needed
to support idmapped base layers with overlay.

Cc: <linux-unionfs@vger.kernel.org>
Tested-by: Giuseppe Scrivano <gscrivan@redhat.com>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
---
 fs/overlayfs/inode.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
index 0b09e62091da..a3fcb61844ff 100644
--- a/fs/overlayfs/inode.c
+++ b/fs/overlayfs/inode.c
@@ -349,6 +349,7 @@ int ovl_xattr_set(struct dentry *dentry, struct inode *inode, const char *name,
 	struct ovl_fs *ofs = OVL_FS(dentry->d_sb);
 	struct dentry *upperdentry = ovl_i_dentry_upper(inode);
 	struct dentry *realdentry = upperdentry ?: ovl_dentry_lower(dentry);
+	struct path realpath;
 	const struct cred *old_cred;
 
 	err = ovl_want_write(dentry);
@@ -356,8 +357,9 @@ int ovl_xattr_set(struct dentry *dentry, struct inode *inode, const char *name,
 		goto out;
 
 	if (!value && !upperdentry) {
+		ovl_path_lower(dentry, &realpath);
 		old_cred = ovl_override_creds(dentry->d_sb);
-		err = vfs_getxattr(&init_user_ns, realdentry, name, NULL, 0);
+		err = vfs_getxattr(mnt_user_ns(realpath.mnt), realdentry, name, NULL, 0);
 		revert_creds(old_cred);
 		if (err < 0)
 			goto out_drop_write;
@@ -395,11 +397,11 @@ int ovl_xattr_get(struct dentry *dentry, struct inode *inode, const char *name,
 {
 	ssize_t res;
 	const struct cred *old_cred;
-	struct dentry *realdentry =
-		ovl_i_dentry_upper(inode) ?: ovl_dentry_lower(dentry);
+	struct path realpath;
 
+	ovl_i_path_real(inode, &realpath);
 	old_cred = ovl_override_creds(dentry->d_sb);
-	res = vfs_getxattr(&init_user_ns, realdentry, name, value, size);
+	res = vfs_getxattr(mnt_user_ns(realpath.mnt), realpath.dentry, name, value, size);
 	revert_creds(old_cred);
 	return res;
 }
-- 
2.32.0