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Alexei Starovoitov Cc: Peter Zijlstra , Arnaldo Carvalho de Melo , Ingo Molnar , "jani.nikula@linux.intel.com" , "joonas.lahtinen@linux.intel.com" , "rodrigo.vivi@intel.com" , "benh@kernel.crashing.org" , Paul Mackerras , Michael Ellerman , "james.bottomley@hansenpartnership.com" , Serge Hallyn , James Morris , Will Deacon , Mark Rutland , Robert Richter , Alexei Starovoitov , Jiri Olsa , Andi Kleen , Stephane Eranian , Igor Lubashev , Alexander Shishkin , Namhyung Kim , Song Liu , Lionel Landwerlin , Thomas Gleixner , linux-kernel , "linux-security-module@vger.kernel.org" , "selinux@vger.kernel.org" , "intel-gfx@lists.freedesktop.org" , "linux-parisc@vger.kernel.org" , "linuxppc-dev@lists.ozlabs.org" , linux-arm-kernel , "linux-perf-users@vger.kernel.org" , oprofile-list@lists.sf.net, Andy Lutomirski References: <0548c832-7f4b-dc4c-8883-3f2b6d351a08@linux.intel.com> <9b77124b-675d-5ac7-3741-edec575bd425@linux.intel.com> <64cab472-806e-38c4-fb26-0ffbee485367@tycho.nsa.gov> <05297eff-8e14-ccdf-55a4-870c64516de8@linux.intel.com> <537bdb28-c9e4-f44f-d665-25250065a6bb@linux.intel.com> <63d9700f-231d-7973-5307-3e56a48c54cb@linux.intel.com> From: Stephen Smalley Message-ID: Date: Wed, 22 Jan 2020 09:07:32 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.3.1 MIME-Version: 1.0 In-Reply-To: <63d9700f-231d-7973-5307-3e56a48c54cb@linux.intel.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-parisc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-parisc@vger.kernel.org On 1/22/20 5:45 AM, Alexey Budankov wrote: > > On 21.01.2020 21:27, Alexey Budankov wrote: >> >> On 21.01.2020 20:55, Alexei Starovoitov wrote: >>> On Tue, Jan 21, 2020 at 9:31 AM Alexey Budankov >>> 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 >>>>>> --- >>>>>> 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. > > So far so good, I suggest using the simplest version for v6: > > static inline bool perfmon_capable(void) > { > return capable(CAP_PERFMON) || capable(CAP_SYS_ADMIN); > } > > It keeps the implementation simple and readable. The implementation is more > performant in the sense of calling the API - one capable() call for CAP_PERFMON > privileged process. > > Yes, it bloats audit log for CAP_SYS_ADMIN privileged and unprivileged processes, > but this bloating also advertises and leverages using more secure CAP_PERFMON > based approach to use perf_event_open system call. I can live with that. We just need to document that when you see both a CAP_PERFMON and a CAP_SYS_ADMIN audit message for a process, try only allowing CAP_PERFMON first and see if that resolves the issue. We have a similar issue with CAP_DAC_READ_SEARCH versus CAP_DAC_OVERRIDE. From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stephen Smalley Subject: Re: [PATCH v5 01/10] capabilities: introduce CAP_PERFMON to kernel and user space Date: Wed, 22 Jan 2020 09:07:32 -0500 Message-ID: References: <0548c832-7f4b-dc4c-8883-3f2b6d351a08@linux.intel.com> <9b77124b-675d-5ac7-3741-edec575bd425@linux.intel.com> <64cab472-806e-38c4-fb26-0ffbee485367@tycho.nsa.gov> <05297eff-8e14-ccdf-55a4-870c64516de8@linux.intel.com> <537bdb28-c9e4-f44f-d665-25250065a6bb@linux.intel.com> <63d9700f-231d-7973-5307-3e56a48c54cb@linux.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <63d9700f-231d-7973-5307-3e56a48c54cb@linux.intel.com> Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org To: Alexey Budankov , Alexei Starovoitov Cc: Peter Zijlstra , Arnaldo Carvalho de Melo , Ingo Molnar , "jani.nikula@linux.intel.com" , "joonas.lahtinen@linux.intel.com" , "rodrigo.vivi@intel.com" , "benh@kernel.crashing.org" , Paul Mackerras , Michael Ellerman , "james.bottomley@hansenpartnership.com" , Serge Hallyn , James Morris , Will Deacon , Mark Rutland , Robert Richter , Alexei Starovoitov , Jiri Olsa Andi Kleen List-Id: linux-perf-users.vger.kernel.org On 1/22/20 5:45 AM, Alexey Budankov wrote: > > On 21.01.2020 21:27, Alexey Budankov wrote: >> >> On 21.01.2020 20:55, Alexei Starovoitov wrote: >>> On Tue, Jan 21, 2020 at 9:31 AM Alexey Budankov >>> 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 >>>>>> --- >>>>>> 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. > > So far so good, I suggest using the simplest version for v6: > > static inline bool perfmon_capable(void) > { > return capable(CAP_PERFMON) || capable(CAP_SYS_ADMIN); > } > > It keeps the implementation simple and readable. The implementation is more > performant in the sense of calling the API - one capable() call for CAP_PERFMON > privileged process. > > Yes, it bloats audit log for CAP_SYS_ADMIN privileged and unprivileged processes, > but this bloating also advertises and leverages using more secure CAP_PERFMON > based approach to use perf_event_open system call. I can live with that. We just need to document that when you see both a CAP_PERFMON and a CAP_SYS_ADMIN audit message for a process, try only allowing CAP_PERFMON first and see if that resolves the issue. We have a similar issue with CAP_DAC_READ_SEARCH versus CAP_DAC_OVERRIDE. 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capabilities: introduce CAP_PERFMON to kernel and user space To: Alexey Budankov , Alexei Starovoitov References: <0548c832-7f4b-dc4c-8883-3f2b6d351a08@linux.intel.com> <9b77124b-675d-5ac7-3741-edec575bd425@linux.intel.com> <64cab472-806e-38c4-fb26-0ffbee485367@tycho.nsa.gov> <05297eff-8e14-ccdf-55a4-870c64516de8@linux.intel.com> <537bdb28-c9e4-f44f-d665-25250065a6bb@linux.intel.com> <63d9700f-231d-7973-5307-3e56a48c54cb@linux.intel.com> From: Stephen Smalley Message-ID: Date: Wed, 22 Jan 2020 09:07:32 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.3.1 MIME-Version: 1.0 In-Reply-To: <63d9700f-231d-7973-5307-3e56a48c54cb@linux.intel.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Mark Rutland , Song Liu , Peter Zijlstra , "joonas.lahtinen@linux.intel.com" , Will Deacon , Alexei Starovoitov , Stephane Eranian , "james.bottomley@hansenpartnership.com" , Paul Mackerras , Jiri Olsa , Andi Kleen , Igor Lubashev , James Morris , Alexander Shishkin , Ingo Molnar , oprofile-list@lists.sf.net, Serge Hallyn , Robert Richter , "selinux@vger.kernel.org" , "intel-gfx@lists.freedesktop.org" , "jani.nikula@linux.intel.com" , Arnaldo Carvalho de Melo , "rodrigo.vivi@intel.com" , Namhyung Kim , Thomas Gleixner , linux-arm-kernel , "linux-parisc@vger.kernel.org" , linux-kernel , Lionel Landwerlin , Andy Lutomirski , "linux-perf-users@vger.kernel.org" , "linux-security-module@vger.kernel.org" , "linuxppc-dev@lists.ozlabs.org" Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On 1/22/20 5:45 AM, Alexey Budankov wrote: > > On 21.01.2020 21:27, Alexey Budankov wrote: >> >> On 21.01.2020 20:55, Alexei Starovoitov wrote: >>> On Tue, Jan 21, 2020 at 9:31 AM Alexey Budankov >>> 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 >>>>>> --- >>>>>> 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. > > So far so good, I suggest using the simplest version for v6: > > static inline bool perfmon_capable(void) > { > return capable(CAP_PERFMON) || capable(CAP_SYS_ADMIN); > } > > It keeps the implementation simple and readable. The implementation is more > performant in the sense of calling the API - one capable() call for CAP_PERFMON > privileged process. > > Yes, it bloats audit log for CAP_SYS_ADMIN privileged and unprivileged processes, > but this bloating also advertises and leverages using more secure CAP_PERFMON > based approach to use perf_event_open system call. I can live with that. We just need to document that when you see both a CAP_PERFMON and a CAP_SYS_ADMIN audit message for a process, try only allowing CAP_PERFMON first and see if that resolves the issue. We have a similar issue with CAP_DAC_READ_SEARCH versus CAP_DAC_OVERRIDE. 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([144.51.242.1]) by EMSM-GH1-UEA10.NCSC.MIL with ESMTP; 22 Jan 2020 14:07:08 +0000 Received: from moss-pluto.infosec.tycho.ncsc.mil (moss-pluto [192.168.25.131]) by tarius.infosec.tycho.ncsc.mil (8.14.7/8.14.4) with ESMTP id 00ME64kn169097; Wed, 22 Jan 2020 09:06:05 -0500 Subject: Re: [PATCH v5 01/10] capabilities: introduce CAP_PERFMON to kernel and user space To: Alexey Budankov , Alexei Starovoitov References: <0548c832-7f4b-dc4c-8883-3f2b6d351a08@linux.intel.com> <9b77124b-675d-5ac7-3741-edec575bd425@linux.intel.com> <64cab472-806e-38c4-fb26-0ffbee485367@tycho.nsa.gov> <05297eff-8e14-ccdf-55a4-870c64516de8@linux.intel.com> <537bdb28-c9e4-f44f-d665-25250065a6bb@linux.intel.com> <63d9700f-231d-7973-5307-3e56a48c54cb@linux.intel.com> From: Stephen Smalley Message-ID: Date: Wed, 22 Jan 2020 09:07:32 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.3.1 MIME-Version: 1.0 In-Reply-To: <63d9700f-231d-7973-5307-3e56a48c54cb@linux.intel.com> Content-Language: en-US X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200122_060742_980815_E7FCC868 X-CRM114-Status: GOOD ( 18.56 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Mark Rutland , Song Liu , Peter Zijlstra , "benh@kernel.crashing.org" , "joonas.lahtinen@linux.intel.com" , Will Deacon , Alexei Starovoitov , Stephane Eranian , "james.bottomley@hansenpartnership.com" , Paul Mackerras , Jiri Olsa , Andi Kleen , Michael Ellerman , Igor Lubashev , James Morris , Alexander Shishkin , Ingo Molnar , oprofile-list@lists.sf.net, Serge Hallyn , Robert Richter , "selinux@vger.kernel.org" , "intel-gfx@lists.freedesktop.org" , "jani.nikula@linux.intel.com" , Arnaldo Carvalho de Melo , "rodrigo.vivi@intel.com" , Namhyung Kim , Thomas Gleixner , linux-arm-kernel , "linux-parisc@vger.kernel.org" , linux-kernel , Lionel Landwerlin , Andy Lutomirski , "linux-perf-users@vger.kernel.org" , "linux-security-module@vger.kernel.org" , "linuxppc-dev@lists.ozlabs.org" Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 1/22/20 5:45 AM, Alexey Budankov wrote: > > On 21.01.2020 21:27, Alexey Budankov wrote: >> >> On 21.01.2020 20:55, Alexei Starovoitov wrote: >>> On Tue, Jan 21, 2020 at 9:31 AM Alexey Budankov >>> 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 >>>>>> --- >>>>>> 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. > > So far so good, I suggest using the simplest version for v6: > > static inline bool perfmon_capable(void) > { > return capable(CAP_PERFMON) || capable(CAP_SYS_ADMIN); > } > > It keeps the implementation simple and readable. The implementation is more > performant in the sense of calling the API - one capable() call for CAP_PERFMON > privileged process. > > Yes, it bloats audit log for CAP_SYS_ADMIN privileged and unprivileged processes, > but this bloating also advertises and leverages using more secure CAP_PERFMON > based approach to use perf_event_open system call. I can live with that. We just need to document that when you see both a CAP_PERFMON and a CAP_SYS_ADMIN audit message for a process, try only allowing CAP_PERFMON first and see if that resolves the issue. We have a similar issue with CAP_DAC_READ_SEARCH versus CAP_DAC_OVERRIDE. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.1 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 61773C33CB6 for ; Thu, 23 Jan 2020 10:23:23 +0000 (UTC) Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client 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=?us-ascii?q?gEBgmM/AYJWJQ+uWIEyhElBQIMwgT6BDioBiUyCY3mBB4E4D4JdPoJkAQIBA?= =?us-ascii?q?oRvgl4EkBaHHEaXWoJDgkuEdI5uBhuDP5c4LY4xiGKUNiOBWCsIAhgIIQ+DJ?= =?us-ascii?q?wkWMRgNiA0XFYhPhV0jAzACBQaNZAEB?= Received: from tarius.tycho.ncsc.mil (HELO tarius.infosec.tycho.ncsc.mil) ([144.51.242.1]) by EMSM-GH1-UEA10.NCSC.MIL with ESMTP; 22 Jan 2020 14:07:08 +0000 Received: from moss-pluto.infosec.tycho.ncsc.mil (moss-pluto [192.168.25.131]) by tarius.infosec.tycho.ncsc.mil (8.14.7/8.14.4) with ESMTP id 00ME64kn169097; Wed, 22 Jan 2020 09:06:05 -0500 To: Alexey Budankov , Alexei Starovoitov References: <0548c832-7f4b-dc4c-8883-3f2b6d351a08@linux.intel.com> <9b77124b-675d-5ac7-3741-edec575bd425@linux.intel.com> <64cab472-806e-38c4-fb26-0ffbee485367@tycho.nsa.gov> <05297eff-8e14-ccdf-55a4-870c64516de8@linux.intel.com> <537bdb28-c9e4-f44f-d665-25250065a6bb@linux.intel.com> <63d9700f-231d-7973-5307-3e56a48c54cb@linux.intel.com> From: Stephen Smalley Message-ID: Date: Wed, 22 Jan 2020 09:07:32 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.3.1 MIME-Version: 1.0 In-Reply-To: <63d9700f-231d-7973-5307-3e56a48c54cb@linux.intel.com> Content-Language: en-US X-Mailman-Approved-At: Thu, 23 Jan 2020 10:23:15 +0000 Subject: Re: [Intel-gfx] [PATCH v5 01/10] capabilities: introduce CAP_PERFMON to kernel and user space X-BeenThere: intel-gfx@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Intel graphics driver community testing & development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Mark Rutland , Song Liu , Peter Zijlstra , "benh@kernel.crashing.org" , Will Deacon , Alexei Starovoitov , Stephane Eranian , "james.bottomley@hansenpartnership.com" , Paul Mackerras , Jiri Olsa , Andi Kleen , Michael Ellerman , Igor Lubashev , James Morris , Alexander Shishkin , Ingo Molnar , oprofile-list@lists.sf.net, Serge Hallyn , Robert Richter , "selinux@vger.kernel.org" , "intel-gfx@lists.freedesktop.org" , Arnaldo Carvalho de Melo , Namhyung Kim , Thomas Gleixner , linux-arm-kernel , "linux-parisc@vger.kernel.org" , linux-kernel , Andy Lutomirski , "linux-perf-users@vger.kernel.org" , "linux-security-module@vger.kernel.org" , "linuxppc-dev@lists.ozlabs.org" Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" On 1/22/20 5:45 AM, Alexey Budankov wrote: > > On 21.01.2020 21:27, Alexey Budankov wrote: >> >> On 21.01.2020 20:55, Alexei Starovoitov wrote: >>> On Tue, Jan 21, 2020 at 9:31 AM Alexey Budankov >>> 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 >>>>>> --- >>>>>> 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. > > So far so good, I suggest using the simplest version for v6: > > static inline bool perfmon_capable(void) > { > return capable(CAP_PERFMON) || capable(CAP_SYS_ADMIN); > } > > It keeps the implementation simple and readable. The implementation is more > performant in the sense of calling the API - one capable() call for CAP_PERFMON > privileged process. > > Yes, it bloats audit log for CAP_SYS_ADMIN privileged and unprivileged processes, > but this bloating also advertises and leverages using more secure CAP_PERFMON > based approach to use perf_event_open system call. I can live with that. We just need to document that when you see both a CAP_PERFMON and a CAP_SYS_ADMIN audit message for a process, try only allowing CAP_PERFMON first and see if that resolves the issue. We have a similar issue with CAP_DAC_READ_SEARCH versus CAP_DAC_OVERRIDE. _______________________________________________ Intel-gfx mailing list Intel-gfx@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/intel-gfx