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Date:      Wed, 3 Jul 2019 00:10:01 +0000 (UTC)
From:      Mark Johnston <markj@FreeBSD.org>
To:        src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org
Subject:   svn commit: r349627 - in head/sys: cam/scsi compat/linux sys
Message-ID:  <201907030010.x630A19M052020@repo.freebsd.org>
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Author: markj
Date: Wed Jul  3 00:10:01 2019
New Revision: 349627
URL: https://svnweb.freebsd.org/changeset/base/349627

Log:
  Remove the CDIOCREADSUBCHANNEL_SYSSPACE ioctl.
  
  This was added for emulation of Linux's CDROMSUBCHNL, but allows
  users with read access to a cd(4) device to overwrite kernel memory
  provided that the driver detects some media present.
  
  Reimplement CDROMSUBCHNL by bouncing the data from CDIOCREADSUBCHANNEL
  through the linux_cdrom_subchnl structure passed from userspace.
  
  admbugs:	768
  Reported by:	Alex Fortune
  Security:	CVE-2019-5602
  Security:	FreeBSD-SA-19:11.cd_ioctl

Modified:
  head/sys/cam/scsi/scsi_cd.c
  head/sys/compat/linux/linux_ioctl.c
  head/sys/sys/cdio.h

Modified: head/sys/cam/scsi/scsi_cd.c
==============================================================================
--- head/sys/cam/scsi/scsi_cd.c	Wed Jul  3 00:04:50 2019	(r349626)
+++ head/sys/cam/scsi/scsi_cd.c	Wed Jul  3 00:10:01 2019	(r349627)
@@ -1314,7 +1314,7 @@ cdioctl(struct disk *dp, u_long cmd, void *addr, int f
 
 	struct 	cam_periph *periph;
 	struct	cd_softc *softc;
-	int	nocopyout, error = 0;
+	int	error = 0;
 
 	periph = (struct cam_periph *)dp->d_drv1;
 	cam_periph_lock(periph);
@@ -1356,7 +1356,6 @@ cdioctl(struct disk *dp, u_long cmd, void *addr, int f
 	 */
 	cam_periph_unlock(periph);
 
-	nocopyout = 0;
 	switch (cmd) {
 
 	case CDIOCPLAYTRACKS:
@@ -1532,9 +1531,6 @@ cdioctl(struct disk *dp, u_long cmd, void *addr, int f
 			cam_periph_unlock(periph);
 		}
 		break;
-	case CDIOCREADSUBCHANNEL_SYSSPACE:
-		nocopyout = 1;
-		/* Fallthrough */
 	case CDIOCREADSUBCHANNEL:
 		{
 			struct ioc_read_subchannel *args
@@ -1579,13 +1575,7 @@ cdioctl(struct disk *dp, u_long cmd, void *addr, int f
 				data->header.data_len[1] +
 				sizeof(struct cd_sub_channel_header)));
 			cam_periph_unlock(periph);
-			if (nocopyout == 0) {
-				if (copyout(data, args->data, len) != 0) {
-					error = EFAULT;
-				}
-			} else {
-				bcopy(data, args->data, len);
-			}
+			error = copyout(data, args->data, len);
 			free(data, M_SCSICD);
 		}
 		break;

Modified: head/sys/compat/linux/linux_ioctl.c
==============================================================================
--- head/sys/compat/linux/linux_ioctl.c	Wed Jul  3 00:04:50 2019	(r349626)
+++ head/sys/compat/linux/linux_ioctl.c	Wed Jul  3 00:10:01 2019	(r349627)
@@ -1489,16 +1489,26 @@ linux_ioctl_cdrom(struct thread *td, struct linux_ioct
 		struct ioc_read_subchannel bsdsc;
 		struct cd_sub_channel_info bsdinfo;
 
+		error = copyin((void *)args->arg, &sc, sizeof(sc));
+		if (error)
+			break;
+
+		/*
+		 * Invoke the native ioctl and bounce the returned data through
+		 * the userspace buffer.  This works because the Linux structure
+		 * is the same size as our structures for the subchannel header
+		 * and position data.
+		 */
 		bsdsc.address_format = CD_LBA_FORMAT;
 		bsdsc.data_format = CD_CURRENT_POSITION;
 		bsdsc.track = 0;
-		bsdsc.data_len = sizeof(bsdinfo);
-		bsdsc.data = &bsdinfo;
-		error = fo_ioctl(fp, CDIOCREADSUBCHANNEL_SYSSPACE,
-		    (caddr_t)&bsdsc, td->td_ucred, td);
+		bsdsc.data_len = sizeof(sc);
+		bsdsc.data = (void *)args->arg;
+		error = fo_ioctl(fp, CDIOCREADSUBCHANNEL, (caddr_t)&bsdsc,
+		    td->td_ucred, td);
 		if (error)
 			break;
-		error = copyin((void *)args->arg, &sc, sizeof(sc));
+		error = copyin((void *)args->arg, &bsdinfo, sizeof(bsdinfo));
 		if (error)
 			break;
 		sc.cdsc_audiostatus = bsdinfo.header.audio_status;

Modified: head/sys/sys/cdio.h
==============================================================================
--- head/sys/sys/cdio.h	Wed Jul  3 00:04:50 2019	(r349626)
+++ head/sys/sys/cdio.h	Wed Jul  3 00:10:01 2019	(r349627)
@@ -274,11 +274,4 @@ struct ioc_capability {			/*<2>*/
 
 #define	CDIOCCAPABILITY	_IOR('c',30,struct ioc_capability)	/*<2>*/
 
-/*
- * Special version of CDIOCREADSUBCHANNEL which assumes that
- * ioc_read_subchannel->data points to the kernel memory. For
- * use in compatibility layers.
- */
-#define CDIOCREADSUBCHANNEL_SYSSPACE _IOWR('c', 31, struct ioc_read_subchannel)
-
 #endif /* !_SYS_CDIO_H_ */

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