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2019-01-29x86/speculation: Add PR_SPEC_DISABLE_NOEXECWaiman Long
With the default SPEC_STORE_BYPASS_SECCOMP/SPEC_STORE_BYPASS_PRCTL mode, the TIF_SSBD bit will be inherited when a new task is fork'ed or cloned. It will also remain when a new program is execve'ed. Only certain class of applications (like Java) that can run on behalf of multiple users on a single thread will require disabling speculative store bypass for security purposes. Those applications will call prctl(2) at startup time to disable SSB. They won't rely on the fact the SSB might have been disabled. Other applications that don't need SSBD will just move on without checking if SSBD has been turned on or not. The fact that the TIF_SSBD is inherited across execve(2) boundary will cause performance of applications that don't need SSBD but their predecessors have SSBD on to be unwittingly impacted especially if they write to memory a lot. To remedy this problem, a new PR_SPEC_DISABLE_NOEXEC argument for the PR_SET_SPECULATION_CTRL option of prctl(2) is added to allow applications to specify that the SSBD feature bit on the task structure should be cleared whenever a new program is being execve'ed. Suggested-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Waiman Long <longman@redhat.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: Borislav Petkov <bp@alien8.de> Cc: Jonathan Corbet <corbet@lwn.net> Cc: linux-doc@vger.kernel.org Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Andi Kleen <ak@linux.intel.com> Cc: David Woodhouse <dwmw@amazon.co.uk> Cc: Jiri Kosina <jikos@kernel.org> Cc: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Tim Chen <tim.c.chen@linux.intel.com> Cc: KarimAllah Ahmed <karahmed@amazon.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> Link: https://lkml.kernel.org/r/1547676096-3281-1-git-send-email-longman@redhat.com
2019-01-02Merge branch 'next-seccomp' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security Pull seccomp updates from James Morris: - Add SECCOMP_RET_USER_NOTIF - seccomp fixes for sparse warnings and s390 build (Tycho) * 'next-seccomp' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security: seccomp, s390: fix build for syscall type change seccomp: fix poor type promotion samples: add an example of seccomp user trap seccomp: add a return code to trap to userspace seccomp: switch system call argument type to void * seccomp: hoist struct seccomp_data recalculation higher
2018-12-11seccomp: add a return code to trap to userspaceTycho Andersen
This patch introduces a means for syscalls matched in seccomp to notify some other task that a particular filter has been triggered. The motivation for this is primarily for use with containers. For example, if a container does an init_module(), we obviously don't want to load this untrusted code, which may be compiled for the wrong version of the kernel anyway. Instead, we could parse the module image, figure out which module the container is trying to load and load it on the host. As another example, containers cannot mount() in general since various filesystems assume a trusted image. However, if an orchestrator knows that e.g. a particular block device has not been exposed to a container for writing, it want to allow the container to mount that block device (that is, handle the mount for it). This patch adds functionality that is already possible via at least two other means that I know about, both of which involve ptrace(): first, one could ptrace attach, and then iterate through syscalls via PTRACE_SYSCALL. Unfortunately this is slow, so a faster version would be to install a filter that does SECCOMP_RET_TRACE, which triggers a PTRACE_EVENT_SECCOMP. Since ptrace allows only one tracer, if the container runtime is that tracer, users inside the container (or outside) trying to debug it will not be able to use ptrace, which is annoying. It also means that older distributions based on Upstart cannot boot inside containers using ptrace, since upstart itself uses ptrace to monitor services while starting. The actual implementation of this is fairly small, although getting the synchronization right was/is slightly complex. Finally, it's worth noting that the classic seccomp TOCTOU of reading memory data from the task still applies here, but can be avoided with careful design of the userspace handler: if the userspace handler reads all of the task memory that is necessary before applying its security policy, the tracee's subsequent memory edits will not be read by the tracer. Signed-off-by: Tycho Andersen <tycho@tycho.ws> CC: Kees Cook <keescook@chromium.org> CC: Andy Lutomirski <luto@amacapital.net> CC: Oleg Nesterov <oleg@redhat.com> CC: Eric W. Biederman <ebiederm@xmission.com> CC: "Serge E. Hallyn" <serge@hallyn.com> Acked-by: Serge Hallyn <serge@hallyn.com> CC: Christian Brauner <christian@brauner.io> CC: Tyler Hicks <tyhicks@canonical.com> CC: Akihiro Suda <suda.akihiro@lab.ntt.co.jp> Signed-off-by: Kees Cook <keescook@chromium.org>
2018-11-28x86/speculation: Add prctl() control for indirect branch speculationThomas Gleixner
Add the PR_SPEC_INDIRECT_BRANCH option for the PR_GET_SPECULATION_CTRL and PR_SET_SPECULATION_CTRL prctls to allow fine grained per task control of indirect branch speculation via STIBP and IBPB. Invocations: Check indirect branch speculation status with - prctl(PR_GET_SPECULATION_CTRL, PR_SPEC_INDIRECT_BRANCH, 0, 0, 0); Enable indirect branch speculation with - prctl(PR_SET_SPECULATION_CTRL, PR_SPEC_INDIRECT_BRANCH, PR_SPEC_ENABLE, 0, 0); Disable indirect branch speculation with - prctl(PR_SET_SPECULATION_CTRL, PR_SPEC_INDIRECT_BRANCH, PR_SPEC_DISABLE, 0, 0); Force disable indirect branch speculation with - prctl(PR_SET_SPECULATION_CTRL, PR_SPEC_INDIRECT_BRANCH, PR_SPEC_FORCE_DISABLE, 0, 0); See Documentation/userspace-api/spec_ctrl.rst. Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Ingo Molnar <mingo@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Andy Lutomirski <luto@kernel.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Jiri Kosina <jkosina@suse.cz> Cc: Tom Lendacky <thomas.lendacky@amd.com> Cc: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: David Woodhouse <dwmw@amazon.co.uk> Cc: Andi Kleen <ak@linux.intel.com> Cc: Dave Hansen <dave.hansen@intel.com> Cc: Casey Schaufler <casey.schaufler@intel.com> Cc: Asit Mallick <asit.k.mallick@intel.com> Cc: Arjan van de Ven <arjan@linux.intel.com> Cc: Jon Masters <jcm@redhat.com> Cc: Waiman Long <longman9394@gmail.com> Cc: Greg KH <gregkh@linuxfoundation.org> Cc: Dave Stewart <david.c.stewart@intel.com> Cc: Kees Cook <keescook@chromium.org> Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/20181125185005.866780996@linutronix.de
2018-06-06Merge tag 'audit-pr-20180605' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/audit Pull audit updates from Paul Moore: "Another reasonable chunk of audit changes for v4.18, thirteen patches in total. The thirteen patches can mostly be broken down into one of four categories: general bug fixes, accessor functions for audit state stored in the task_struct, negative filter matches on executable names, and extending the (relatively) new seccomp logging knobs to the audit subsystem. The main driver for the accessor functions from Richard are the changes we're working on to associate audit events with containers, but I think they have some standalone value too so I figured it would be good to get them in now. The seccomp/audit patches from Tyler apply the seccomp logging improvements from a few releases ago to audit's seccomp logging; starting with this patchset the changes in /proc/sys/kernel/seccomp/actions_logged should apply to both the standard kernel logging and audit. As usual, everything passes the audit-testsuite and it happens to merge cleanly with your tree" [ Heh, except it had trivial merge conflicts with the SELinux tree that also came in from Paul - Linus ] * tag 'audit-pr-20180605' of git://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/audit: audit: Fix wrong task in comparison of session ID audit: use existing session info function audit: normalize loginuid read access audit: use new audit_context access funciton for seccomp_actions_logged audit: use inline function to set audit context audit: use inline function to get audit context audit: convert sessionid unset to a macro seccomp: Don't special case audited processes when logging seccomp: Audit attempts to modify the actions_logged sysctl seccomp: Configurable separator for the actions_logged string seccomp: Separate read and write code for actions_logged sysctl audit: allow not equal op for audit by executable audit: add syscall information to FEATURE_CHANGE records
2018-05-09Documentation/spec_ctrl: Do some minor cleanupsBorislav Petkov
Fix some typos, improve formulations, end sentences with a fullstop. Signed-off-by: Borislav Petkov <bp@suse.de> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2018-05-08seccomp: Don't special case audited processes when loggingTyler Hicks
Seccomp logging for "handled" actions such as RET_TRAP, RET_TRACE, or RET_ERRNO can be very noisy for processes that are being audited. This patch modifies the seccomp logging behavior to treat processes that are being inspected via the audit subsystem the same as processes that aren't under inspection. Handled actions will no longer be logged just because the process is being inspected. Since v4.14, applications have the ability to request logging of handled actions by using the SECCOMP_FILTER_FLAG_LOG flag when loading seccomp filters. With this patch, the logic for deciding if an action will be logged is: if action == RET_ALLOW: do not log else if action not in actions_logged: do not log else if action == RET_KILL: log else if action == RET_LOG: log else if filter-requests-logging: log else: do not log Reported-by: Steve Grubb <sgrubb@redhat.com> Signed-off-by: Tyler Hicks <tyhicks@canonical.com> Acked-by: Kees Cook <keescook@chromium.org> Signed-off-by: Paul Moore <paul@paul-moore.com>
2018-05-05prctl: Add force disable speculationThomas Gleixner
For certain use cases it is desired to enforce mitigations so they cannot be undone afterwards. That's important for loader stubs which want to prevent a child from disabling the mitigation again. Will also be used for seccomp(). The extra state preserving of the prctl state for SSB is a preparatory step for EBPF dymanic speculation control. Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2018-05-03prctl: Add speculation control prctlsThomas Gleixner
Add two new prctls to control aspects of speculation related vulnerabilites and their mitigations to provide finer grained control over performance impacting mitigations. PR_GET_SPECULATION_CTRL returns the state of the speculation misfeature which is selected with arg2 of prctl(2). The return value uses bit 0-2 with the following meaning: Bit Define Description 0 PR_SPEC_PRCTL Mitigation can be controlled per task by PR_SET_SPECULATION_CTRL 1 PR_SPEC_ENABLE The speculation feature is enabled, mitigation is disabled 2 PR_SPEC_DISABLE The speculation feature is disabled, mitigation is enabled If all bits are 0 the CPU is not affected by the speculation misfeature. If PR_SPEC_PRCTL is set, then the per task control of the mitigation is available. If not set, prctl(PR_SET_SPECULATION_CTRL) for the speculation misfeature will fail. PR_SET_SPECULATION_CTRL allows to control the speculation misfeature, which is selected by arg2 of prctl(2) per task. arg3 is used to hand in the control value, i.e. either PR_SPEC_ENABLE or PR_SPEC_DISABLE. The common return values are: EINVAL prctl is not implemented by the architecture or the unused prctl() arguments are not 0 ENODEV arg2 is selecting a not supported speculation misfeature PR_SET_SPECULATION_CTRL has these additional return values: ERANGE arg3 is incorrect, i.e. it's not either PR_SPEC_ENABLE or PR_SPEC_DISABLE ENXIO prctl control of the selected speculation misfeature is disabled The first supported controlable speculation misfeature is PR_SPEC_STORE_BYPASS. Add the define so this can be shared between architectures. Based on an initial patch from Tim Chen and mostly rewritten. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Ingo Molnar <mingo@kernel.org> Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2017-08-14seccomp: Implement SECCOMP_RET_KILL_PROCESS actionKees Cook
Right now, SECCOMP_RET_KILL_THREAD (neé SECCOMP_RET_KILL) kills the current thread. There have been a few requests for this to kill the entire process (the thread group). This cannot be just changed (discovered when adding coredump support since coredumping kills the entire process) because there are userspace programs depending on the thread-kill behavior. Instead, implement SECCOMP_RET_KILL_PROCESS, which is 0x80000000, and can be processed as "-1" by the kernel, below the existing RET_KILL that is ABI-set to "0". For userspace, SECCOMP_RET_ACTION_FULL is added to expand the mask to the signed bit. Old userspace using the SECCOMP_RET_ACTION mask will see SECCOMP_RET_KILL_PROCESS as 0 still, but this would only be visible when examining the siginfo in a core dump from a RET_KILL_*, where it will think it was thread-killed instead of process-killed. Attempts to introduce this behavior via other ways (filter flags, seccomp struct flags, masked RET_DATA bits) all come with weird side-effects and baggage. This change preserves the central behavioral expectations of the seccomp filter engine without putting too great a burden on changes needed in userspace to use the new action. The new action is discoverable by userspace through either the new actions_avail sysctl or through the SECCOMP_GET_ACTION_AVAIL seccomp operation. If used without checking for availability, old kernels will treat RET_KILL_PROCESS as RET_KILL_THREAD (since the old mask will produce RET_KILL_THREAD). Cc: Paul Moore <paul@paul-moore.com> Cc: Fabricio Voznika <fvoznika@google.com> Signed-off-by: Kees Cook <keescook@chromium.org>
2017-08-14seccomp: Rename SECCOMP_RET_KILL to SECCOMP_RET_KILL_THREADKees Cook
In preparation for adding SECCOMP_RET_KILL_PROCESS, rename SECCOMP_RET_KILL to the more accurate SECCOMP_RET_KILL_THREAD. The existing selftest values are intentionally left as SECCOMP_RET_KILL just to be sure we're exercising the alias. Signed-off-by: Kees Cook <keescook@chromium.org>
2017-08-14seccomp: Action to log before allowingTyler Hicks
Add a new action, SECCOMP_RET_LOG, that logs a syscall before allowing the syscall. At the implementation level, this action is identical to the existing SECCOMP_RET_ALLOW action. However, it can be very useful when initially developing a seccomp filter for an application. The developer can set the default action to be SECCOMP_RET_LOG, maybe mark any obviously needed syscalls with SECCOMP_RET_ALLOW, and then put the application through its paces. A list of syscalls that triggered the default action (SECCOMP_RET_LOG) can be easily gleaned from the logs and that list can be used to build the syscall whitelist. Finally, the developer can change the default action to the desired value. This provides a more friendly experience than seeing the application get killed, then updating the filter and rebuilding the app, seeing the application get killed due to a different syscall, then updating the filter and rebuilding the app, etc. The functionality is similar to what's supported by the various LSMs. SELinux has permissive mode, AppArmor has complain mode, SMACK has bring-up mode, etc. SECCOMP_RET_LOG is given a lower value than SECCOMP_RET_ALLOW as allow while logging is slightly more restrictive than quietly allowing. Unfortunately, the tests added for SECCOMP_RET_LOG are not capable of inspecting the audit log to verify that the syscall was logged. With this patch, the logic for deciding if an action will be logged is: if action == RET_ALLOW: do not log else if action == RET_KILL && RET_KILL in actions_logged: log else if action == RET_LOG && RET_LOG in actions_logged: log else if filter-requests-logging && action in actions_logged: log else if audit_enabled && process-is-being-audited: log else: do not log Signed-off-by: Tyler Hicks <tyhicks@canonical.com> Signed-off-by: Kees Cook <keescook@chromium.org>
2017-08-14seccomp: Sysctl to configure actions that are allowed to be loggedTyler Hicks
Adminstrators can write to this sysctl to set the seccomp actions that are allowed to be logged. Any actions not found in this sysctl will not be logged. For example, all SECCOMP_RET_KILL, SECCOMP_RET_TRAP, and SECCOMP_RET_ERRNO actions would be loggable if "kill trap errno" were written to the sysctl. SECCOMP_RET_TRACE actions would not be logged since its string representation ("trace") wasn't present in the sysctl value. The path to the sysctl is: /proc/sys/kernel/seccomp/actions_logged The actions_avail sysctl can be read to discover the valid action names that can be written to the actions_logged sysctl with the exception of "allow". SECCOMP_RET_ALLOW actions cannot be configured for logging. The default setting for the sysctl is to allow all actions to be logged except SECCOMP_RET_ALLOW. While only SECCOMP_RET_KILL actions are currently logged, an upcoming patch will allow applications to request additional actions to be logged. There's one important exception to this sysctl. If a task is specifically being audited, meaning that an audit context has been allocated for the task, seccomp will log all actions other than SECCOMP_RET_ALLOW despite the value of actions_logged. This exception preserves the existing auditing behavior of tasks with an allocated audit context. With this patch, the logic for deciding if an action will be logged is: if action == RET_ALLOW: do not log else if action == RET_KILL && RET_KILL in actions_logged: log else if audit_enabled && task-is-being-audited: log else: do not log Signed-off-by: Tyler Hicks <tyhicks@canonical.com> Signed-off-by: Kees Cook <keescook@chromium.org>
2017-08-14seccomp: Sysctl to display available actionsTyler Hicks
This patch creates a read-only sysctl containing an ordered list of seccomp actions that the kernel supports. The ordering, from left to right, is the lowest action value (kill) to the highest action value (allow). Currently, a read of the sysctl file would return "kill trap errno trace allow". The contents of this sysctl file can be useful for userspace code as well as the system administrator. The path to the sysctl is: /proc/sys/kernel/seccomp/actions_avail libseccomp and other userspace code can easily determine which actions the current kernel supports. The set of actions supported by the current kernel may be different than the set of action macros found in kernel headers that were installed where the userspace code was built. In addition, this sysctl will allow system administrators to know which actions are supported by the kernel and make it easier to configure exactly what seccomp logs through the audit subsystem. Support for this level of logging configuration will come in a future patch. Signed-off-by: Tyler Hicks <tyhicks@canonical.com> Signed-off-by: Kees Cook <keescook@chromium.org>
2017-05-18doc: ReSTify no_new_privs.txtKees Cook
This updates no_new_privs documentation to ReST markup and adds it to the user-space API documentation. Signed-off-by: Kees Cook <keescook@chromium.org> Signed-off-by: Jonathan Corbet <corbet@lwn.net>
2017-05-18doc: ReSTify seccomp_filter.txtKees Cook
This updates seccomp_filter.txt for ReST markup, and moves it under the user-space API index, since it describes how application author can use seccomp. Signed-off-by: Kees Cook <keescook@chromium.org> Signed-off-by: Jonathan Corbet <corbet@lwn.net>
2017-05-18doc-rst: fix inline emphasis in unshare.rstMarkus Heiser
The asterisk of the pointer is interpreted as a start tag for inline emphasis. Asterisks which are not Sphinx markup need to be quoted in rst-files. This fixes the Sphinx warning: Documentation/userspace-api/unshare.rst:108: WARNING: Inline emphasis start-string without end-string. Signed-off-by: Markus Heiser <markus.heiser@darmarit.de> Signed-off-by: Jonathan Corbet <corbet@lwn.net>
2017-04-02docs: Convert unshare.txt to RST and add to the user-space API manualJonathan Corbet
This is a straightforward conversion, without any real textual changes. Since this document has seen no substantive changes since its addition in 2006, some such changes are probably warranted. Signed-off-by: Jonathan Corbet <corbet@lwn.net>
2017-04-02docs: Create a user-space API guideJonathan Corbet
This is meant to be the place for documentation relevant to application developers. It's empty for the moment, but at least we have a place now! Signed-off-by: Jonathan Corbet <corbet@lwn.net>