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device_cgroup: Cleanup cgroup eBPF device filter code 

Original cgroup v2 eBPF code for filtering device access made it
possible to compile with CONFIG_CGROUP_DEVICE=n and still use the eBPF
filtering. Change
commit 4b7d4d453f ("device_cgroup: Export devcgroup_check_permission")
reverted this, making it required to set it to y.

Since the device filtering (and all the docs) for cgroup v2 is no longer
a "device controller" like it was in v1, someone might compile their
kernel with CONFIG_CGROUP_DEVICE=n. Then (for linux 5.5+) the eBPF
filter will not be invoked, and all processes will be allowed access
to all devices, no matter what the eBPF filter says.

Signed-off-by: Odin Ugedal <odin@ugedal.com>
Acked-by: Roman Gushchin <guro@fb.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
5.9.x+fslc
Odin Ugedal 2020-04-03 19:55:28 +02:00 committed by Tejun Heo
parent 772b314066
commit eec8fd0277
4 changed files with 23 additions and 14 deletions
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2
drivers/gpu/drm/amd/amdkfd/kfd_priv.h
View File

@ -1050,7 +1050,7 @@ void kfd_dec_compute_active(struct kfd_dev *dev);
/* Check with device cgroup if @kfd device is accessible */
static inline int kfd_devcgroup_check_permission(struct kfd_dev *kfd)
{
#if defined(CONFIG_CGROUP_DEVICE)
#if defined(CONFIG_CGROUP_DEVICE) || defined(CONFIG_CGROUP_BPF)
struct drm_device *ddev = kfd->ddev;
return devcgroup_check_permission(DEVCG_DEV_CHAR, ddev->driver->major,

14
include/linux/device_cgroup.h
View File

@ -1,6 +1,5 @@
/* SPDX-License-Identifier: GPL-2.0 */
#include <linux/fs.h>
#include <linux/bpf-cgroup.h>
#define DEVCG_ACC_MKNOD 1
#define DEVCG_ACC_READ 2
@ -11,16 +10,10 @@
#define DEVCG_DEV_CHAR 2
#define DEVCG_DEV_ALL 4 /* this represents all devices */
#ifdef CONFIG_CGROUP_DEVICE
int devcgroup_check_permission(short type, u32 major, u32 minor,
short access);
#else
static inline int devcgroup_check_permission(short type, u32 major, u32 minor,
short access)
{ return 0; }
#endif
#if defined(CONFIG_CGROUP_DEVICE) || defined(CONFIG_CGROUP_BPF)
int devcgroup_check_permission(short type, u32 major, u32 minor,
short access);
static inline int devcgroup_inode_permission(struct inode *inode, int mask)
{
short type, access = 0;
@ -61,6 +54,9 @@ static inline int devcgroup_inode_mknod(int mode, dev_t dev)
}
#else
static inline int devcgroup_check_permission(short type, u32 major, u32 minor,
short access)
{ return 0; }
static inline int devcgroup_inode_permission(struct inode *inode, int mask)
{ return 0; }
static inline int devcgroup_inode_mknod(int mode, dev_t dev)

2
security/Makefile
View File

@ -30,7 +30,7 @@ obj-$(CONFIG_SECURITY_YAMA) += yama/
obj-$(CONFIG_SECURITY_LOADPIN) += loadpin/
obj-$(CONFIG_SECURITY_SAFESETID) += safesetid/
obj-$(CONFIG_SECURITY_LOCKDOWN_LSM) += lockdown/
obj-$(CONFIG_CGROUP_DEVICE) += device_cgroup.o
obj-$(CONFIG_CGROUPS) += device_cgroup.o
obj-$(CONFIG_BPF_LSM) += bpf/
# Object integrity file lists

19
security/device_cgroup.c
View File

@ -15,6 +15,8 @@
#include <linux/rcupdate.h>
#include <linux/mutex.h>
#ifdef CONFIG_CGROUP_DEVICE
static DEFINE_MUTEX(devcgroup_mutex);
enum devcg_behavior {
@ -792,7 +794,7 @@ struct cgroup_subsys devices_cgrp_subsys = {
};
/**
* __devcgroup_check_permission - checks if an inode operation is permitted
* devcgroup_legacy_check_permission - checks if an inode operation is permitted
* @dev_cgroup: the dev cgroup to be tested against
* @type: device type
* @major: device major number
@ -801,7 +803,7 @@ struct cgroup_subsys devices_cgrp_subsys = {
*
* returns 0 on success, -EPERM case the operation is not permitted
*/
static int __devcgroup_check_permission(short type, u32 major, u32 minor,
static int devcgroup_legacy_check_permission(short type, u32 major, u32 minor,
short access)
{
struct dev_cgroup *dev_cgroup;
@ -825,6 +827,10 @@ static int __devcgroup_check_permission(short type, u32 major, u32 minor,
return 0;
}
#endif /* CONFIG_CGROUP_DEVICE */
#if defined(CONFIG_CGROUP_DEVICE) || defined(CONFIG_CGROUP_BPF)
int devcgroup_check_permission(short type, u32 major, u32 minor, short access)
{
int rc = BPF_CGROUP_RUN_PROG_DEVICE_CGROUP(type, major, minor, access);
@ -832,6 +838,13 @@ int devcgroup_check_permission(short type, u32 major, u32 minor, short access)
if (rc)
return -EPERM;
return __devcgroup_check_permission(type, major, minor, access);
#ifdef CONFIG_CGROUP_DEVICE
return devcgroup_legacy_check_permission(type, major, minor, access);
#else /* CONFIG_CGROUP_DEVICE */
return 0;
#endif /* CONFIG_CGROUP_DEVICE */
}
EXPORT_SYMBOL(devcgroup_check_permission);
#endif /* defined(CONFIG_CGROUP_DEVICE) || defined(CONFIG_CGROUP_BPF) */