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 <jeffb...@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: _______________________________________________ svn-src-head@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/svn-src-head To unsubscribe, send any mail to "svn-src-head-unsubscr...@freebsd.org"
