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From:   Christian Brauner <christian.brauner@ubuntu.com>
To:     =?UTF-8?q?St=C3=A9phane=20Graber?= <stgraber@ubuntu.com>,
        "Eric W. Biederman" <ebiederm@xmission.com>,
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Cc:     smbarber@chromium.org, Seth Forshee <seth.forshee@canonical.com>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        Alexey Dobriyan <adobriyan@gmail.com>,
        Serge Hallyn <serge@hallyn.com>,
        James Morris <jmorris@namei.org>,
        Kees Cook <keescook@chromium.org>,
        Jonathan Corbet <corbet@lwn.net>,
        Phil Estes <estesp@gmail.com>, linux-kernel@vger.kernel.org,
        linux-fsdevel@vger.kernel.org,
        containers@lists.linux-foundation.org,
        linux-security-module@vger.kernel.org, linux-api@vger.kernel.org,
        Christian Brauner <christian.brauner@ubuntu.com>
Subject: [PATCH v2 17/28] inode: inode_owner_or_capable(): handle fsid mappings
Date:   Fri, 14 Feb 2020 19:35:43 +0100
Message-Id: <20200214183554.1133805-18-christian.brauner@ubuntu.com>
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Switch inode_owner_or_capable() to lookup fsids in the fsid mappings. If no
fsid mappings are setup the behavior is unchanged, i.e. fsids are looked up in
the id mappings.

Filesystems that share a superblock in all user namespaces they are mounted in
will retain their old semantics even with the introduction of fsidmappings.

Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
---
/* v2 */
unchanged
---
 fs/inode.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/fs/inode.c b/fs/inode.c
index 7d57068b6b7a..81d7a30b381d 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -21,6 +21,7 @@
 #include <linux/ratelimit.h>
 #include <linux/list_lru.h>
 #include <linux/iversion.h>
+#include <linux/fsuidgid.h>
 #include <trace/events/writeback.h>
 #include "internal.h"
 
@@ -2087,8 +2088,12 @@ bool inode_owner_or_capable(const struct inode *inode)
 		return true;
 
 	ns = current_user_ns();
-	if (kuid_has_mapping(ns, inode->i_uid) && ns_capable(ns, CAP_FOWNER))
+	if (is_userns_visible(inode->i_sb->s_iflags)) {
+		if (kuid_has_mapping(ns, inode->i_uid) && ns_capable(ns, CAP_FOWNER))
+			return true;
+	} else if (kfsuid_has_mapping(ns, inode->i_uid) && ns_capable(ns, CAP_FOWNER)) {
 		return true;
+	}
 	return false;
 }
 EXPORT_SYMBOL(inode_owner_or_capable);
-- 
2.25.0