<div dir="ltr">Hi (patch author here),<div> </div><div>This is my first "real" patch, so looking forward to some feedback! I am not sure if this behavior is the "best one", or if we should require CONFIG_CGROUP_DEVICE to be set to yes. In that case we can just abandon this patch and replace the original "#if defined(CONFIG_CGROUP_DEVICE) || defined(CONFIG_CGROUP_BPF)" with a simple "#ifdef CONFIG_CGROUP_DEVICE" and update the docs and the config.</div><div> </div><div>It is also another alternative to keep the code in this patch and move some of it into a separate file in order to avoid all the ifdefs, and to make the split between cgroup v1 and cgroup v2 code cleaner.</div><div> </div><div>As a reference, only Fedora is currently shipping with cgroup v2 as default (afaik.) and their kernel is compiled (5.3.7-301.fc31.x86_64) with CONFIG_CGROUP_DEVICE=y and CONFIG_CGROUP_BPF=y, so this will not affect them.</div><div> </div><div>Odin Ugedal</div></div> <div class="gmail_quote"><div dir="ltr" class="gmail_attr">fre. 3. apr. 2020 kl. 19:55 skrev Odin Ugedal <<a href="mailto:odin@ugedal.com">odin@ugedal.com</a>>: </div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">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 4b7d4d453fc4 ("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 <<a href="mailto:odin@ugedal.com" target="_blank">odin@ugedal.com</a>> --- drivers/gpu/drm/amd/amdkfd/kfd_priv.h | 2 +- include/linux/device_cgroup.h | 14 +++++--------- security/Makefile | 2 +- security/device_cgroup.c | 19 ++++++++++++++++--- 4 files changed, 23 insertions(+), 14 deletions(-) diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_priv.h b/drivers/gpu/drm/amd/amdkfd/kfd_priv.h index 4a3049841086..c24cad3c64ed 100644 --- a/drivers/gpu/drm/amd/amdkfd/kfd_priv.h +++ b/drivers/gpu/drm/amd/amdkfd/kfd_priv.h @@ -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, diff --git a/include/linux/device_cgroup.h b/include/linux/device_cgroup.h index fa35b52e0002..9a72214496e5 100644 --- a/include/linux/device_cgroup.h +++ b/include/linux/device_cgroup.h @@ -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) diff --git a/security/Makefile b/security/Makefile index 22e73a3482bd..3baf435de541 100644 --- a/security/Makefile +++ b/security/Makefile @@ -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 diff --git a/security/device_cgroup.c b/security/device_cgroup.c index 7d0f8f7431ff..43ab0ad45c1b 100644 --- a/security/device_cgroup.c +++ b/security/device_cgroup.c @@ -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) */ -- 2.26.0 </blockquote></div>