userns: Pass a userns parameter into posix_acl_to_xattr and posix_acl_from_xattr

 - Pass the user namespace the uid and gid values in the xattr are stored
   in into posix_acl_from_xattr.

 - Pass the user namespace kuid and kgid values should be converted into
   when storing uid and gid values in an xattr in posix_acl_to_xattr.

- Modify all callers of posix_acl_from_xattr and posix_acl_to_xattr to
  pass in &init_user_ns.

In the short term this change is not strictly needed but it makes the
code clearer.  In the longer term this change is necessary to be able to
mount filesystems outside of the initial user namespace that natively
store posix acls in the linux xattr format.

Cc: Theodore Tso <tytso@mit.edu>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andreas Dilger <adilger.kernel@dilger.ca>
Cc: Jan Kara <jack@suse.cz>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>

1 files changed, 8 insertions, 6 deletions

diff --git a/fs/xattr_acl.c b/fs/xattr_acl.c
index bf472ca..11efd83 100644
--- a/fs/xattr_acl.c
+++ b/fs/xattr_acl.c
@@ -73,7 +73,8 @@ void posix_acl_fix_xattr_to_user(void *value, size_t size)
  * Convert from extended attribute to in-memory representation.
  */
 struct posix_acl *
-posix_acl_from_xattr(const void *value, size_t size)
+posix_acl_from_xattr(struct user_namespace *user_ns,
+		     const void *value, size_t size)
 {
 	posix_acl_xattr_header *header = (posix_acl_xattr_header *)value;
 	posix_acl_xattr_entry *entry = (posix_acl_xattr_entry *)(header+1), *end;
@@ -112,14 +113,14 @@ posix_acl_from_xattr(const void *value, size_t size)
 
 			case ACL_USER:
 				acl_e->e_uid =
-					make_kuid(&init_user_ns,
+					make_kuid(user_ns,
 						  le32_to_cpu(entry->e_id));
 				if (!uid_valid(acl_e->e_uid))
 					goto fail;
 				break;
 			case ACL_GROUP:
 				acl_e->e_gid =
-					make_kgid(&init_user_ns,
+					make_kgid(user_ns,
 						  le32_to_cpu(entry->e_id));
 				if (!gid_valid(acl_e->e_gid))
 					goto fail;
@@ -141,7 +142,8 @@ EXPORT_SYMBOL (posix_acl_from_xattr);
  * Convert from in-memory to extended attribute representation.
  */
 int
-posix_acl_to_xattr(const struct posix_acl *acl, void *buffer, size_t size)
+posix_acl_to_xattr(struct user_namespace *user_ns, const struct posix_acl *acl,
+		   void *buffer, size_t size)
 {
 	posix_acl_xattr_header *ext_acl = (posix_acl_xattr_header *)buffer;
 	posix_acl_xattr_entry *ext_entry = ext_acl->a_entries;
@@ -162,11 +164,11 @@ posix_acl_to_xattr(const struct posix_acl *acl, void *buffer, size_t size)
 		switch(acl_e->e_tag) {
 		case ACL_USER:
 			ext_entry->e_id =
-				cpu_to_le32(from_kuid(&init_user_ns, acl_e->e_uid));
+				cpu_to_le32(from_kuid(user_ns, acl_e->e_uid));
 			break;
 		case ACL_GROUP:
 			ext_entry->e_id =
-				cpu_to_le32(from_kgid(&init_user_ns, acl_e->e_gid));
+				cpu_to_le32(from_kgid(user_ns, acl_e->e_gid));
 			break;
 		default:
 			ext_entry->e_id = cpu_to_le32(ACL_UNDEFINED_ID);