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Add a jail parameter, allow.kmem, which lets jailed processes access

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/dev/kmem and related devices (i.e. grants PRIV_IO and PRIV_KMEM_WRITE).
This in conjunction with changing the drm driver's permission check from
PRIV_DRIVER to PRIV_KMEM_WRITE will allow a jailed Xorg server.

Submitted by:	netchild
MFC after:	1 week
This commit is contained in:
Jamie Gritton 2014-01-29 13:41:13 +00:00
parent 9c1ca3a1dd
commit 109ca2d5f1
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=261266
4 changed files with 41 additions and 2 deletions
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4
sys/dev/drm/drmP.h
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@ -227,7 +227,9 @@ enum {
#define PAGE_ALIGN(addr) round_page(addr)
/* DRM_SUSER returns true if the user is superuser */
#if __FreeBSD_version >= 700000
#if __FreeBSD_version >= 1000000
#define DRM_SUSER(p) (priv_check(p, PRIV_KMEM_WRITE) == 0)
#elif __FreeBSD_version >= 700000
#define DRM_SUSER(p) (priv_check(p, PRIV_DRIVER) == 0)
#else
#define DRM_SUSER(p) (suser(p) == 0)

25
sys/kern/kern_jail.c
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@ -208,6 +208,7 @@ static char *pr_allow_names[] = {
"allow.mount.zfs",
"allow.mount.procfs",
"allow.mount.tmpfs",
"allow.kmem",
};
const size_t pr_allow_names_size = sizeof(pr_allow_names);
@ -224,6 +225,7 @@ static char *pr_allow_nonames[] = {
"allow.mount.nozfs",
"allow.mount.noprocfs",
"allow.mount.notmpfs",
"allow.nokmem",
};
const size_t pr_allow_nonames_size = sizeof(pr_allow_nonames);
@ -3950,6 +3952,27 @@ prison_priv_check(struct ucred *cred, int priv)
case PRIV_NETINET_GETCRED:
return (0);
/*
* Allow access to /dev/io in a jail if the non-jailed admin
* requests this and if /dev/io exists in the jail. This
* allows Xorg to probe a card.
*/
case PRIV_IO:
if (cred->cr_prison->pr_allow & PR_ALLOW_KMEM)
return (0);
else
return (EPERM);
/*
* Allow low level access to KMEM-like devices (e.g. to
* allow Xorg to use DRI).
*/
case PRIV_KMEM_WRITE:
if (cred->cr_prison->pr_allow & PR_ALLOW_KMEM)
return (0);
else
return (EPERM);
/*
* Allow jailed root to set loginclass.
*/
@ -4384,6 +4407,8 @@ SYSCTL_JAIL_PARAM(_allow, quotas, CTLTYPE_INT | CTLFLAG_RW,
"B", "Jail may set file quotas");
SYSCTL_JAIL_PARAM(_allow, socket_af, CTLTYPE_INT | CTLFLAG_RW,
"B", "Jail may create sockets other than just UNIX/IPv4/IPv6/route");
SYSCTL_JAIL_PARAM(_allow, kmem, CTLTYPE_INT | CTLFLAG_RW,
"B", "Jail may access kmem-like devices (io, dri) if they exist");
SYSCTL_JAIL_PARAM_SUBNODE(allow, mount, "Jail mount/unmount permission flags");
SYSCTL_JAIL_PARAM(_allow_mount, , CTLTYPE_INT | CTLFLAG_RW,

3
sys/sys/jail.h
View File

@ -228,7 +228,8 @@ struct prison_racct {
#define PR_ALLOW_MOUNT_ZFS 0x0200
#define PR_ALLOW_MOUNT_PROCFS 0x0400
#define PR_ALLOW_MOUNT_TMPFS 0x0800
#define PR_ALLOW_ALL 0x0fff
#define PR_ALLOW_KMEM 0x1000
#define PR_ALLOW_ALL 0x1fff
/*
* OSD methods

11
usr.sbin/jail/jail.8
View File

@ -573,6 +573,17 @@ with non-jailed parts of the system.
Sockets within a jail are normally restricted to IPv4, IPv6, local
(UNIX), and route. This allows access to other protocol stacks that
have not had jail functionality added to them.
.It Va allow.kmem
Jailed processes may access
.Pa /dev/kmem
and similar devices (e.g. io, dri) if they have sufficient permission
(via the usual file permissions).
Note that the device files must exist within the jail for this parameter
to be of any use;
the default devfs ruleset for jails does not include any such devices.
Giving a jail access to kernel memory obviates much of the security that
jails offer, but can still be useful for other purposes.
For example, this would allow the Xorg server to run inside a jail.
.El
.El
.Pp