svn commit: r363051 - in head: lib/libc/sys sys/kern
Mark Johnston
markj at FreeBSD.org
Thu Jul 9 17:26:50 UTC 2020
Author: markj
Date: Thu Jul 9 17:26:49 2020
New Revision: 363051
URL: https://svnweb.freebsd.org/changeset/base/363051
Log:
Avoid copying out kernel pointers from msgctl(IPC_STAT).
While this behaviour is harmless, it is really just an artifact of the
fact that the msgctl(2) implementation uses a user-visible structure as
part of the internal implementation, so it is not deliberate and these
pointers are not useful to userspace. Thus, NULL them out before
copying out, and remove references to them from the manual page.
Reported by: Jeffball <jeffball at grimm-co.com>
Reviewed by: emaste, kib
MFC after: 1 week
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D25600
Modified:
head/lib/libc/sys/msgctl.2
head/sys/kern/sysv_msg.c
Modified: head/lib/libc/sys/msgctl.2
==============================================================================
--- head/lib/libc/sys/msgctl.2 Thu Jul 9 17:12:22 2020 (r363050)
+++ head/lib/libc/sys/msgctl.2 Thu Jul 9 17:26:49 2020 (r363051)
@@ -31,7 +31,7 @@
.\"
.\" $FreeBSD$
.\"/
-.Dd July 9, 2009
+.Dd July 9, 2020
.Dt MSGCTL 2
.Os
.Sh NAME
@@ -63,8 +63,6 @@ and contains (amongst others) the following members:
.Bd -literal
struct msqid_ds {
struct ipc_perm msg_perm; /* msg queue permission bits */
- struct msg *__msg_first; /* kernel data, don't use */
- struct msg *__msg_last; /* kernel data, don't use */
msglen_t msg_cbytes; /* number of bytes in use on the queue */
msgqnum_t msg_qnum; /* number of msgs in the queue */
msglen_t msg_qbytes; /* max # of bytes on the queue */
Modified: head/sys/kern/sysv_msg.c
==============================================================================
--- head/sys/kern/sysv_msg.c Thu Jul 9 17:12:22 2020 (r363050)
+++ head/sys/kern/sysv_msg.c Thu Jul 9 17:26:49 2020 (r363051)
@@ -613,6 +613,13 @@ kern_msgctl(struct thread *td, int msqid, int cmd, str
*msqbuf = msqkptr->u;
if (td->td_ucred->cr_prison != msqkptr->cred->cr_prison)
msqbuf->msg_perm.key = IPC_PRIVATE;
+
+ /*
+ * Try to hide the fact that the structure layout is shared by
+ * both the kernel and userland. These pointers are not useful
+ * to userspace.
+ */
+ msqbuf->__msg_first = msqbuf->__msg_last = NULL;
break;
default:
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