pidfs: add missing BUILD_BUG_ON() assert on struct pidfd_info

[ Upstream commit d8fc51d ]

Validate that the size of struct pidfd_info is correctly updated.

Link: https://patch.msgid.link/20251028-work-coredump-signal-v1-4-ca449b7b7aa0@kernel.org
Fixes: 1d8db6f ("pidfs, coredump: add PIDFD_INFO_COREDUMP")
Reviewed-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@canonical.com>
Reviewed-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

Author: brauner

fs/pidfs.c

@@ -306,6 +306,8 @@ static long pidfd_info(struct file *file, unsigned int cmd, unsigned long arg)
 	const struct cred *c;
 	__u64 mask;
 
+	BUILD_BUG_ON(sizeof(struct pidfd_info) != PIDFD_INFO_SIZE_VER1);
+
 	if (!uinfo)
 		return -EINVAL;
 	if (usize < PIDFD_INFO_SIZE_VER0)