OS-5412 'screen' doesn't run on centos7

Reviewed by: Patrick Mooney <patrick.mooney@joyent.com>
Reviewed by: Ryan Zezeski <ryan.zeseski@joyent.com>
Approved by: Patrick Mooney <patrick.mooney@joyent.com>

4 files changed, 100 insertions, 5 deletions

diff --git a/usr/src/lib/brand/lx/lx_support/lx_support.c b/usr/src/lib/brand/lx/lx_support/lx_support.c
index 65679b0603..ef4e614e99 100644
--- a/usr/src/lib/brand/lx/lx_support/lx_support.c
+++ b/usr/src/lib/brand/lx/lx_support/lx_support.c
@@ -21,7 +21,7 @@
 /*
  * Copyright 2009 Sun Microsystems, Inc.  All rights reserved.
  * Use is subject to license terms.
- * Copyright 2016 Joyent, Inc.
+ * Copyright 2017 Joyent, Inc.
  */
 
 /*
@@ -163,6 +163,72 @@ lxs_getattrs(zone_dochandle_t zdh, char **krelease)
 		lxs_err(gettext("error accessing zone configuration"));
 }
 
+/*
+ * Attempt to lookup the "tty" gid from within the zone's /etc/group file.
+ * The gid is used to emulate existing Linux udev behavior for setting the gid
+ * on a pty. If we cannot lookup the gid for some reason, we still allow
+ * the zone to boot.
+ *
+ * Because we're reading the lx zone's /etc/group file, we have to parse it
+ * ourselves, but this is simple since we only need the gid.
+ */
+static void
+lxs_set_ttygid(zoneid_t zoneid)
+{
+	char	buf[MAXPATHLEN];
+	FILE	*fp;
+	gid_t	tty_gid = 0;
+
+	if (snprintf(buf, sizeof (buf), "%s/root/etc/group", zoneroot) >=
+	    sizeof (buf))
+		return;
+
+	if ((fp = fopen(buf, "r")) == NULL)
+		return;
+
+	/*
+	 * Look for the "tty" line and get the gid. Note that this loop will
+	 * properly handle a long line that won't fit into buf on a single
+	 * fgets. The subsequent fgets will consume more of the line but we
+	 * continue on through that. In practice this is unlikely to occur.
+	 */
+	while (fgets(buf, sizeof (buf), fp) != NULL) {
+		char *p, *p_id;
+		long val;
+
+		/* group name */
+		if ((p = strchr(buf, ':')) == NULL)
+			continue;
+		*p = '\0';
+		if (strcmp(buf, "tty") != 0)
+			continue;
+
+		/* found tty entry, skip the "x" field */
+		if ((p = strchr(p + 1, ':')) == NULL)
+			goto done;
+		/* gid field */
+		p_id = p + 1;
+		if ((p = strchr(p_id, ':')) == NULL)
+			goto done;
+		*p = '\0';
+
+		errno = 0;
+		val = strtol(p_id, &p, 10);
+		/* Perform simple validation on the gid */
+		if (errno != 0 || *p != '\0' || val > MAXUID || val < 0)
+			goto done;
+		tty_gid = (gid_t)val;
+		break;
+	}
+
+	if (tty_gid != 0)
+		(void) zone_setattr(zoneid, LX_ATTR_TTY_GID, &tty_gid,
+		    sizeof (tty_gid));
+
+done:
+	fclose(fp);
+}
+
 static int
 lxs_boot()
 {
@@ -205,6 +271,8 @@ lxs_boot()
 			lxs_err(gettext("unable to set kernel version"));
 	}
 
+	lxs_set_ttygid(zoneid);
+
 	return (0);
 }
 
diff --git a/usr/src/uts/common/brand/lx/os/lx_brand.c b/usr/src/uts/common/brand/lx/os/lx_brand.c
index 4fbf8530bb..839ff9219a 100644
--- a/usr/src/uts/common/brand/lx/os/lx_brand.c
+++ b/usr/src/uts/common/brand/lx/os/lx_brand.c
@@ -25,7 +25,7 @@
  */
 
 /*
- * Copyright 2016, Joyent, Inc. All rights reserved.
+ * Copyright 2017, Joyent, Inc. All rights reserved.
  */
 
 /*
@@ -408,6 +408,19 @@ lx_setattr(zone_t *zone, int attr, void *ubuf, size_t ubufsz)
 		mutex_exit(&lxzd->lxzd_lock);
 		return (0);
 	}
+	case LX_ATTR_TTY_GID: {
+		gid_t	gid;
+		if (ubufsz != sizeof (gid)) {
+			return (ERANGE);
+		}
+		if (copyin(ubuf, &gid, ubufsz) != 0) {
+			return (EFAULT);
+		}
+		mutex_enter(&lxzd->lxzd_lock);
+		lxzd->lxzd_ttygrp = gid;
+		mutex_exit(&lxzd->lxzd_lock);
+		return (0);
+	}
 	default:
 		return (EINVAL);
 	}
diff --git a/usr/src/uts/common/brand/lx/sys/lx_brand.h b/usr/src/uts/common/brand/lx/sys/lx_brand.h
index 8e239a4f2a..147e8961f2 100644
--- a/usr/src/uts/common/brand/lx/sys/lx_brand.h
+++ b/usr/src/uts/common/brand/lx/sys/lx_brand.h
@@ -24,7 +24,7 @@
  */
 
 /*
- * Copyright 2016 Joyent, Inc.
+ * Copyright 2017 Joyent, Inc.
  */
 
 #ifndef _LX_BRAND_H
@@ -162,6 +162,7 @@ typedef enum lx_ptrace_options {
 
 #define	LX_ATTR_KERN_RELEASE	ZONE_ATTR_BRAND_ATTRS
 #define	LX_ATTR_KERN_VERSION	(ZONE_ATTR_BRAND_ATTRS + 1)
+#define	LX_ATTR_TTY_GID		(ZONE_ATTR_BRAND_ATTRS + 2)
 
 /*
  * Aux vector containing phdr of Linux executable and ehdr of interpreter
@@ -606,6 +607,7 @@ typedef struct lx_zone_data {
 	char lxzd_kernel_version[LX_KERN_VERSION_MAX];
 	ksocket_t lxzd_ioctl_sock;
 	char lxzd_bootid[LX_BOOTID_LEN];	/* procfs boot_id */
+	gid_t lxzd_ttygrp;			/* tty gid for pty chown */
 	vfs_t *lxzd_cgroup;			/* cgroup for this zone */
 	list_t *lxzd_vdisks;			/* virtual disks (zvols) */
 	dev_t lxzd_zfs_dev;			/* major num for zfs */
diff --git a/usr/src/uts/common/brand/lx/syscall/lx_ioctl.c b/usr/src/uts/common/brand/lx/syscall/lx_ioctl.c
index 17dff2a840..88b025643f 100644
--- a/usr/src/uts/common/brand/lx/syscall/lx_ioctl.c
+++ b/usr/src/uts/common/brand/lx/syscall/lx_ioctl.c
@@ -10,7 +10,7 @@
  */
 
 /*
- * Copyright 2016 Joyent, Inc.
+ * Copyright 2017 Joyent, Inc.
  */
 
 #include <sys/errno.h>
@@ -1021,6 +1021,7 @@ ict_gptn(file_t *fp, int cmd, intptr_t arg, int lxcmd)
 	pt_own_t pto;
 	int error, rv;
 	int ptyno;
+	lx_zone_data_t *lxzd = ztolxzd(curproc->p_zone);
 
 	/* This operation is only valid for the lx_ptm device. */
 	if (getmajor(fp->f_vnode->v_rdev) != ddi_name_to_major(LX_PTM_DRV))
@@ -1028,7 +1029,18 @@ ict_gptn(file_t *fp, int cmd, intptr_t arg, int lxcmd)
 
 	cr = CRED();
 	pto.pto_ruid = cr->cr_uid;
-	pto.pto_rgid = cr->cr_gid;
+	/*
+	 * Both Linux and our native code (see grantpt() in native libc)
+	 * prefer assigning the "tty" gid to the new pty. On Linux this is
+	 * done by udev. Since we're in the kernel we cannot lookup the gid, so
+	 * we rely on the lx_support program to initialize the value in the
+	 * zone data at boot time.
+	 */
+	if (lxzd->lxzd_ttygrp == 0) {
+		pto.pto_rgid = cr->cr_gid;
+	} else {
+		pto.pto_rgid = lxzd->lxzd_ttygrp;
+	}
 
 	istr.ic_cmd = OWNERPT;
 	istr.ic_len = sizeof (pto);