Patch "af_unix: Fix msg_controllen test in scm_pidfd_recv() for MSG_CMSG_COMPAT." has been added to the 6.5-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    af_unix: Fix msg_controllen test in scm_pidfd_recv() for MSG_CMSG_COMPAT.

to the 6.5-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     af_unix-fix-msg_controllen-test-in-scm_pidfd_recv-fo.patch
and it can be found in the queue-6.5 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 80c87260ca4afe5783fc347125857c90aa9012ac
Author: Kuniyuki Iwashima <kuniyu@xxxxxxxxxx>
Date:   Fri Sep 1 16:46:04 2023 -0700

    af_unix: Fix msg_controllen test in scm_pidfd_recv() for MSG_CMSG_COMPAT.
    
    [ Upstream commit 718e6b51298e0f254baca0d40ab52a00e004e014 ]
    
    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 <hca@xxxxxxxxxxxxx>
    Closes: https://lore.kernel.org/netdev/20230901200517.8742-A-hca@xxxxxxxxxxxxx/
    Signed-off-by: Kuniyuki Iwashima <kuniyu@xxxxxxxxxx>
    Tested-by: Heiko Carstens <hca@xxxxxxxxxxxxx>
    Reviewed-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@xxxxxxxxxxxxx>
    Reviewed-by: Michal Swiatkowski <michal.swiatkowski@xxxxxxxxxxxxxxx>
    Acked-by: Christian Brauner <brauner@xxxxxxxxxx>
    Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/include/net/scm.h b/include/net/scm.h
index c5bcdf65f55c9..e8c76b4be2fe7 100644
--- a/include/net/scm.h
+++ b/include/net/scm.h
@@ -9,6 +9,7 @@
 #include <linux/pid.h>
 #include <linux/nsproxy.h>
 #include <linux/sched/signal.h>
+#include <net/compat.h>
 
 /* 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;
 	}