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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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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)