Messages in this thread | | | Subject | Re: [PATCH v5 01/10] capabilities: introduce CAP_PERFMON to kernel and user space | From | Stephen Smalley <> | Date | Tue, 21 Jan 2020 09:43:49 -0500 |
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On 1/20/20 6:23 AM, Alexey Budankov wrote: > > Introduce CAP_PERFMON capability designed to secure system performance > monitoring and observability operations so that CAP_PERFMON would assist > CAP_SYS_ADMIN capability in its governing role for perf_events, i915_perf > and other performance monitoring and observability subsystems. > > CAP_PERFMON intends to harden system security and integrity during system > performance monitoring and observability operations by decreasing attack > surface that is available to a CAP_SYS_ADMIN privileged process [1]. > Providing access to system performance monitoring and observability > operations under CAP_PERFMON capability singly, without the rest of > CAP_SYS_ADMIN credentials, excludes chances to misuse the credentials and > makes operation more secure. > > CAP_PERFMON intends to take over CAP_SYS_ADMIN credentials related to > system performance monitoring and observability operations and balance > amount of CAP_SYS_ADMIN credentials following the recommendations in the > capabilities man page [1] for CAP_SYS_ADMIN: "Note: this capability is > overloaded; see Notes to kernel developers, below." > > Although the software running under CAP_PERFMON can not ensure avoidance > of related hardware issues, the software can still mitigate these issues > following the official embargoed hardware issues mitigation procedure [2]. > The bugs in the software itself could be fixed following the standard > kernel development process [3] to maintain and harden security of system > performance monitoring and observability operations. > > [1] http://man7.org/linux/man-pages/man7/capabilities.7.html > [2] https://www.kernel.org/doc/html/latest/process/embargoed-hardware-issues.html > [3] https://www.kernel.org/doc/html/latest/admin-guide/security-bugs.html > > Signed-off-by: Alexey Budankov <alexey.budankov@linux.intel.com> > --- > include/linux/capability.h | 12 ++++++++++++ > include/uapi/linux/capability.h | 8 +++++++- > security/selinux/include/classmap.h | 4 ++-- > 3 files changed, 21 insertions(+), 3 deletions(-) > > diff --git a/include/linux/capability.h b/include/linux/capability.h > index ecce0f43c73a..8784969d91e1 100644 > --- a/include/linux/capability.h > +++ b/include/linux/capability.h > @@ -251,6 +251,18 @@ extern bool privileged_wrt_inode_uidgid(struct user_namespace *ns, const struct > extern bool capable_wrt_inode_uidgid(const struct inode *inode, int cap); > extern bool file_ns_capable(const struct file *file, struct user_namespace *ns, int cap); > extern bool ptracer_capable(struct task_struct *tsk, struct user_namespace *ns); > +static inline bool perfmon_capable(void) > +{ > + struct user_namespace *ns = &init_user_ns; > + > + if (ns_capable_noaudit(ns, CAP_PERFMON)) > + return ns_capable(ns, CAP_PERFMON); > + > + if (ns_capable_noaudit(ns, CAP_SYS_ADMIN)) > + return ns_capable(ns, CAP_SYS_ADMIN); > + > + return false; > +}
Why _noaudit()? Normally only used when a permission failure is non-fatal to the operation. Otherwise, we want the audit message.
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