From 718e6b51298e0f254baca0d40ab52a00e004e014 Mon Sep 17 00:00:00 2001 From: Kuniyuki Iwashima Date: Fri, 1 Sep 2023 16:46:04 -0700 Subject: [PATCH] af_unix: Fix msg_controllen test in scm_pidfd_recv() for MSG_CMSG_COMPAT. Heiko Carstens reported that SCM_PIDFD does not work with MSG_CMSG_COMPAT because scm_pidfd_recv() always checks msg_controllen against sizeof(struct cmsghdr). We need to use sizeof(struct compat_cmsghdr) for the compat case. Fixes: 5e2ff6704a27 ("scm: add SO_PASSPIDFD and SCM_PIDFD") Reported-by: Heiko Carstens Closes: https://lore.kernel.org/netdev/20230901200517.8742-A-hca@linux.ibm.com/ Signed-off-by: Kuniyuki Iwashima Tested-by: Heiko Carstens Reviewed-by: Alexander Mikhalitsyn Reviewed-by: Michal Swiatkowski Acked-by: Christian Brauner Signed-off-by: David S. Miller --- include/net/scm.h | 14 +++++++++----- 1 file changed, 9 insertions(+), 5 deletions(-) diff --git a/include/net/scm.h b/include/net/scm.h index c5bcdf6..e8c76b4 100644 --- a/include/net/scm.h +++ b/include/net/scm.h @@ -9,6 +9,7 @@ #include #include #include +#include /* Well, we should have at least one descriptor open * to accept passed FDs 8) @@ -123,14 +124,17 @@ static inline bool scm_has_secdata(struct socket *sock) static __inline__ void scm_pidfd_recv(struct msghdr *msg, struct scm_cookie *scm) { struct file *pidfd_file = NULL; - int pidfd; + int len, pidfd; - /* - * put_cmsg() doesn't return an error if CMSG is truncated, + /* put_cmsg() doesn't return an error if CMSG is truncated, * that's why we need to opencode these checks here. */ - if ((msg->msg_controllen <= sizeof(struct cmsghdr)) || - (msg->msg_controllen - sizeof(struct cmsghdr)) < sizeof(int)) { + if (msg->msg_flags & MSG_CMSG_COMPAT) + len = sizeof(struct compat_cmsghdr) + sizeof(int); + else + len = sizeof(struct cmsghdr) + sizeof(int); + + if (msg->msg_controllen < len) { msg->msg_flags |= MSG_CTRUNC; return; } -- 2.7.4