1 files changed, 85 insertions, 5 deletions

diff --git a/fs/xattr_acl.c b/fs/xattr_acl.c
index 69d06b0..bf472ca 100644
--- a/fs/xattr_acl.c
+++ b/fs/xattr_acl.c
@@ -9,7 +9,65 @@
 #include <linux/fs.h>
 #include <linux/posix_acl_xattr.h>
 #include <linux/gfp.h>
+#include <linux/user_namespace.h>
 
+/*
+ * Fix up the uids and gids in posix acl extended attributes in place.
+ */
+static void posix_acl_fix_xattr_userns(
+	struct user_namespace *to, struct user_namespace *from,
+	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;
+	int count;
+	kuid_t uid;
+	kgid_t gid;
+
+	if (!value)
+		return;
+	if (size < sizeof(posix_acl_xattr_header))
+		return;
+	if (header->a_version != cpu_to_le32(POSIX_ACL_XATTR_VERSION))
+		return;
+
+	count = posix_acl_xattr_count(size);
+	if (count < 0)
+		return;
+	if (count == 0)
+		return;
+
+	for (end = entry + count; entry != end; entry++) {
+		switch(le16_to_cpu(entry->e_tag)) {
+		case ACL_USER:
+			uid = make_kuid(from, le32_to_cpu(entry->e_id));
+			entry->e_id = cpu_to_le32(from_kuid(to, uid));
+			break;
+		case ACL_GROUP:
+			gid = make_kgid(from, le32_to_cpu(entry->e_id));
+			entry->e_id = cpu_to_le32(from_kuid(to, uid));
+			break;
+		default:
+			break;
+		}
+	}
+}
+
+void posix_acl_fix_xattr_from_user(void *value, size_t size)
+{
+	struct user_namespace *user_ns = current_user_ns();
+	if (user_ns == &init_user_ns)
+		return;
+	posix_acl_fix_xattr_userns(&init_user_ns, user_ns, value, size);
+}
+
+void posix_acl_fix_xattr_to_user(void *value, size_t size)
+{
+	struct user_namespace *user_ns = current_user_ns();
+	if (user_ns == &init_user_ns)
+		return;
+	posix_acl_fix_xattr_userns(user_ns, &init_user_ns, value, size);
+}
 
 /*
  * Convert from extended attribute to in-memory representation.
@@ -50,12 +108,21 @@ posix_acl_from_xattr(const void *value, size_t size)
 			case ACL_GROUP_OBJ:
 			case ACL_MASK:
 			case ACL_OTHER:
-				acl_e->e_id = ACL_UNDEFINED_ID;
 				break;
 
 			case ACL_USER:
+				acl_e->e_uid =
+					make_kuid(&init_user_ns,
+						  le32_to_cpu(entry->e_id));
+				if (!uid_valid(acl_e->e_uid))
+					goto fail;
+				break;
 			case ACL_GROUP:
-				acl_e->e_id = le32_to_cpu(entry->e_id);
+				acl_e->e_gid =
+					make_kgid(&init_user_ns,
+						  le32_to_cpu(entry->e_id));
+				if (!gid_valid(acl_e->e_gid))
+					goto fail;
 				break;
 
 			default:
@@ -89,9 +156,22 @@ posix_acl_to_xattr(const struct posix_acl *acl, void *buffer, size_t size)
 	ext_acl->a_version = cpu_to_le32(POSIX_ACL_XATTR_VERSION);
 
 	for (n=0; n < acl->a_count; n++, ext_entry++) {
-		ext_entry->e_tag  = cpu_to_le16(acl->a_entries[n].e_tag);
-		ext_entry->e_perm = cpu_to_le16(acl->a_entries[n].e_perm);
-		ext_entry->e_id   = cpu_to_le32(acl->a_entries[n].e_id);
+		const struct posix_acl_entry *acl_e = &acl->a_entries[n];
+		ext_entry->e_tag  = cpu_to_le16(acl_e->e_tag);
+		ext_entry->e_perm = cpu_to_le16(acl_e->e_perm);
+		switch(acl_e->e_tag) {
+		case ACL_USER:
+			ext_entry->e_id =
+				cpu_to_le32(from_kuid(&init_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));
+			break;
+		default:
+			ext_entry->e_id = cpu_to_le32(ACL_UNDEFINED_ID);
+			break;
+		}
 	}
 	return real_size;
 }