1 files changed, 26 insertions, 8 deletions

diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c
index 71fefb30e015..64864fb40b40 100644
--- a/fs/notify/fanotify/fanotify_user.c
+++ b/fs/notify/fanotify/fanotify_user.c
@@ -424,11 +424,18 @@ static ssize_t copy_event_to_user(struct fsnotify_group *group,
 	 * events generated by the listener process itself, without disclosing
 	 * the pids of other processes.
 	 */
-	if (!capable(CAP_SYS_ADMIN) &&
+	if (FAN_GROUP_FLAG(group, FANOTIFY_UNPRIV) &&
 	    task_tgid(current) != event->pid)
 		metadata.pid = 0;
 
-	if (path && path->mnt && path->dentry) {
+	/*
+	 * For now, fid mode is required for an unprivileged listener and
+	 * fid mode does not report fd in events.  Keep this check anyway
+	 * for safety in case fid mode requirement is relaxed in the future
+	 * to allow unprivileged listener to get events with no fd and no fid.
+	 */
+	if (!FAN_GROUP_FLAG(group, FANOTIFY_UNPRIV) &&
+	    path && path->mnt && path->dentry) {
 		fd = create_fd(group, path, &f);
 		if (fd < 0)
 			return fd;
@@ -464,7 +471,7 @@ static ssize_t copy_event_to_user(struct fsnotify_group *group,
 					info_type, fanotify_info_name(info),
 					info->name_len, buf, count);
 		if (ret < 0)
-			return ret;
+			goto out_close_fd;
 
 		buf += ret;
 		count -= ret;
@@ -512,7 +519,7 @@ static ssize_t copy_event_to_user(struct fsnotify_group *group,
 					fanotify_event_object_fh(event),
 					info_type, dot, dot_len, buf, count);
 		if (ret < 0)
-			return ret;
+			goto out_close_fd;
 
 		buf += ret;
 		count -= ret;
@@ -1040,6 +1047,7 @@ SYSCALL_DEFINE2(fanotify_init, unsigned int, flags, unsigned int, event_f_flags)
 	int f_flags, fd;
 	unsigned int fid_mode = flags & FANOTIFY_FID_BITS;
 	unsigned int class = flags & FANOTIFY_CLASS_BITS;
+	unsigned int internal_flags = 0;
 
 	pr_debug("%s: flags=%x event_f_flags=%x\n",
 		 __func__, flags, event_f_flags);
@@ -1053,6 +1061,13 @@ SYSCALL_DEFINE2(fanotify_init, unsigned int, flags, unsigned int, event_f_flags)
 		 */
 		if ((flags & FANOTIFY_ADMIN_INIT_FLAGS) || !fid_mode)
 			return -EPERM;
+
+		/*
+		 * Setting the internal flag FANOTIFY_UNPRIV on the group
+		 * prevents setting mount/filesystem marks on this group and
+		 * prevents reporting pid and open fd in events.
+		 */
+		internal_flags |= FANOTIFY_UNPRIV;
 	}
 
 #ifdef CONFIG_AUDITSYSCALL
@@ -1105,7 +1120,7 @@ SYSCALL_DEFINE2(fanotify_init, unsigned int, flags, unsigned int, event_f_flags)
 		goto out_destroy_group;
 	}
 
-	group->fanotify_data.flags = flags;
+	group->fanotify_data.flags = flags | internal_flags;
 	group->memcg = get_mem_cgroup_from_mm(current->mm);
 
 	group->fanotify_data.merge_hash = fanotify_alloc_merge_hash();
@@ -1305,11 +1320,13 @@ static int do_fanotify_mark(int fanotify_fd, unsigned int flags, __u64 mask,
 	group = f.file->private_data;
 
 	/*
-	 * An unprivileged user is not allowed to watch a mount point nor
-	 * a filesystem.
+	 * An unprivileged user is not allowed to setup mount nor filesystem
+	 * marks.  This also includes setting up such marks by a group that
+	 * was initialized by an unprivileged user.
 	 */
 	ret = -EPERM;
-	if (!capable(CAP_SYS_ADMIN) &&
+	if ((!capable(CAP_SYS_ADMIN) ||
+	     FAN_GROUP_FLAG(group, FANOTIFY_UNPRIV)) &&
 	    mark_type != FAN_MARK_INODE)
 		goto fput_and_out;
 
@@ -1460,6 +1477,7 @@ static int __init fanotify_user_setup(void)
 	max_marks = clamp(max_marks, FANOTIFY_OLD_DEFAULT_MAX_MARKS,
 				     FANOTIFY_DEFAULT_MAX_USER_MARKS);
 
+	BUILD_BUG_ON(FANOTIFY_INIT_FLAGS & FANOTIFY_INTERNAL_GROUP_FLAGS);
 	BUILD_BUG_ON(HWEIGHT32(FANOTIFY_INIT_FLAGS) != 10);
 	BUILD_BUG_ON(HWEIGHT32(FANOTIFY_MARK_FLAGS) != 9);