linux-kernel - [PATCH v2 09/10] ovl: do not get metacopy for userxattr

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Date:   Mon,  7 Dec 2020 17:32:54 +0100
From:   Miklos Szeredi <mszeredi@...hat.com>
To:     "Eric W . Biederman" <ebiederm@...ssion.com>
Cc:     linux-fsdevel@...r.kernel.org, linux-unionfs@...r.kernel.org,
        linux-security-module@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH v2 09/10] ovl: do not get metacopy for userxattr

When looking up an inode on the lower layer for which the mounter lacks
read permisison the metacopy check will fail.  This causes the lookup to
fail as well, even though the directory is readable.

So ignore EACCES for the "userxattr" case and assume no metacopy for the
unreadable file.

Signed-off-by: Miklos Szeredi <mszeredi@...hat.com>
---
 fs/overlayfs/util.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/fs/overlayfs/util.c b/fs/overlayfs/util.c
index 66eaf4db027f..703c6e529f39 100644
--- a/fs/overlayfs/util.c
+++ b/fs/overlayfs/util.c
@@ -880,6 +880,13 @@ int ovl_check_metacopy_xattr(struct ovl_fs *ofs, struct dentry *dentry)
 	if (res < 0) {
 		if (res == -ENODATA || res == -EOPNOTSUPP)
 			return 0;
+		/*
+		 * getxattr on user.* may fail with EACCES in case there's no
+		 * read permission on the inode.  Not much we can do, other than
+		 * tell the caller that this is not a metacopy inode.
+		 */
+		if (ofs->config.userxattr && res == -EACCES)
+			return 0;
 		goto out;
 	}
 
-- 
2.26.2