Re: [PATCH v4 14/16] ima: Use mac_admin_ns_capable() to check corresponding capability
From: Christian Brauner <hidden>
Date: 2021-12-08 12:40:47
Also in:
linux-security-module, lkml
On Tue, Dec 07, 2021 at 03:21:25PM -0500, Stefan Berger wrote:
quoted hunk ↗ jump to hunk
Use mac_admin_ns_capable() to check corresponding capability to allow read/write IMA policy without CAP_SYS_ADMIN but with CAP_MAC_ADMIN. Signed-off-by: Denis Semakin <redacted> Signed-off-by: Stefan Berger <stefanb@linux.ibm.com> --- include/linux/capability.h | 6 ++++++ security/integrity/ima/ima_fs.c | 2 +- 2 files changed, 7 insertions(+), 1 deletion(-)diff --git a/include/linux/capability.h b/include/linux/capability.h index 65efb74c3585..991579178f32 100644 --- a/include/linux/capability.h +++ b/include/linux/capability.h@@ -270,6 +270,12 @@ static inline bool checkpoint_restore_ns_capable(struct user_namespace *ns) ns_capable(ns, CAP_SYS_ADMIN); } +static inline bool mac_admin_ns_capable(struct user_namespace *ns) +{ + return ns_capable(ns, CAP_MAC_ADMIN) || + ns_capable(ns, CAP_SYS_ADMIN); +} + /* audit system wants to get cap info from files as well */ int get_vfs_caps_from_disk(struct user_namespace *mnt_userns, const struct dentry *dentry,diff --git a/security/integrity/ima/ima_fs.c b/security/integrity/ima/ima_fs.c index 0e582ceecc7f..a749a3e79304 100644 --- a/security/integrity/ima/ima_fs.c +++ b/security/integrity/ima/ima_fs.c@@ -394,7 +394,7 @@ static int ima_open_policy(struct inode *inode, struct file *filp) #else if ((filp->f_flags & O_ACCMODE) != O_RDONLY) return -EACCES; - if (!capable(CAP_SYS_ADMIN)) + if (!mac_admin_ns_capable(ns->user_ns)) return -EPERM;
Hm, couldn't this rather just be: if (ns_capable(ns, CAP_MAC_ADMIN) || capable(CAP_SYS_ADMIN)) so we don't carry CAP_SYS_ADMIN as an alternative way for ima into user namespaces as well? This way containers don't need to drop CAP_SYS_ADMIN just to prevent mac policy from being altered. But that's more on the LSM side of questions.