[PATCH 08/24] inode: inode_owner_or_capable(): handle fsid mappings

[Christian Brauner]

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 at ubuntu.com>
---
 fs/inode.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/fs/inode.c b/fs/inode.c
index 96d62d97694e..c1ed43c5054c 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -20,6 +20,7 @@
 #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"
 
@@ -2083,8 +2084,12 @@ 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