Commit eec8fd02 authored by Odin Ugedal's avatar Odin Ugedal Committed by Tejun Heo
Browse files

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 4b7d4d45 ("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: default avatarOdin Ugedal <odin@ugedal.com>
Acked-by: default avatarRoman Gushchin <guro@fb.com>
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
parent 772b3140

drivers/gpu/drm/amd/amdkfd/kfd_priv.h

+1 −1
Original line number Diff line number Diff line
@@ -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,

include/linux/device_cgroup.h

+5 −9
Original line number Diff line number Diff line 
/* 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)

security/Makefile

+1 −1
Original line number Diff line number Diff line
@@ -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

security/device_cgroup.c

+16 −3
Original line number Diff line number Diff line
@@ -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) */

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