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device_cgroup: Cleanup cgroup eBPF device filter code

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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>
This commit is contained in:
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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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) */