On 21.01.2020 20:55, Alexei Starovoitov wrote: > On Tue, Jan 21, 2020 at 9:31 AM Alexey Budankov > <alexey.budankov@xxxxxxxxxxxxxxx> wrote: >> >> >> On 21.01.2020 17:43, Stephen Smalley wrote: >>> 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@xxxxxxxxxxxxxxx> >>>> --- >>>> 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. >> >> Some of ideas from v4 review. > > well, in the requested changes form v4 I wrote: > return capable(CAP_PERFMON); > instead of > return false; Aww, indeed. I was concerning exactly about it when updating the patch and simply put false, missing the fact that capable() also logs. I suppose the idea is originally from here [1]. BTW, Has it already seen any _more optimal_ implementation? Anyway, original or optimized version could be reused for CAP_PERFMON. ~Alexey [1] https://patchwork.ozlabs.org/patch/1159243/ > > That's what Andy suggested earlier for CAP_BPF. > I think that should resolve Stephen's concern. >
