kernel/linux.git/security/selinux/include, branch v5.10.53

selinux: add proper NULL termination to the secclass_map permissions

2021-05-14T07:49:59+00:00

commit e4c82eafb609c2badc56f4e11bc50fcf44b8e9eb upstream. This patch adds the missing NULL termination to the "bpf" and "perf_event" object class permission lists. This missing NULL termination should really only affect the tools under scripts/selinux, with the most important being genheaders.c, although in practice this has not been an issue on any of my dev/test systems. If the problem were to manifest itself it would likely result in bogus permissions added to the end of the object class; thankfully with no access control checks using these bogus permissions and no policies defining these permissions the impact would likely be limited to some noise about undefined permissions during policy load. Cc: stable@vger.kernel.org Fixes: ec27c3568a34 ("selinux: bpf: Add selinux check for eBPF syscall operations") Fixes: da97e18458fb ("perf_event: Add support for LSM and SELinux checks") Signed-off-by: Paul Moore Signed-off-by: Greg Kroah-Hartman

selinux: fix variable scope issue in live sidtab conversion

2021-03-30T12:31:53+00:00

commit 6406887a12ee5dcdaffff1a8508d91113d545559 upstream. Commit 02a52c5c8c3b ("selinux: move policy commit after updating selinuxfs") moved the selinux_policy_commit() call out of security_load_policy() into sel_write_load(), which caused a subtle yet rather serious bug. The problem is that security_load_policy() passes a reference to the convert_params local variable to sidtab_convert(), which stores it in the sidtab, where it may be accessed until the policy is swapped over and RCU synchronized. Before 02a52c5c8c3b, selinux_policy_commit() was called directly from security_load_policy(), so the convert_params pointer remained valid all the way until the old sidtab was destroyed, but now that's no longer the case and calls to sidtab_context_to_sid() on the old sidtab after security_load_policy() returns may cause invalid memory accesses. This can be easily triggered using the stress test from commit ee1a84fdfeed ("selinux: overhaul sidtab to fix bug and improve performance"): ``` function rand_cat() { echo $(( $RANDOM % 1024 )) } function do_work() { while true; do echo -n "system_u:system_r:kernel_t:s0:c$(rand_cat),c$(rand_cat)" \ >/sys/fs/selinux/context 2>/dev/null || true done } do_work >/dev/null & do_work >/dev/null & do_work >/dev/null & while load_policy; do echo -n .; sleep 0.1; done kill %1 kill %2 kill %3 ``` Fix this by allocating the temporary sidtab convert structures dynamically and passing them among the selinux_policy_{load,cancel,commit} functions. Fixes: 02a52c5c8c3b ("selinux: move policy commit after updating selinuxfs") Cc: stable@vger.kernel.org Tested-by: Tyler Hicks Reviewed-by: Tyler Hicks Signed-off-by: Ondrej Mosnacek [PM: merge fuzz in security.h and services.c] Signed-off-by: Paul Moore Signed-off-by: Greg Kroah-Hartman

selinux: Add helper functions to get and set checkreqprot

2020-09-15T18:36:28+00:00

checkreqprot data member in selinux_state struct is accessed directly by SELinux functions to get and set. This could cause unexpected read or write access to this data member due to compiler optimizations and/or compiler's reordering of access to this field. Add helper functions to get and set checkreqprot data member in selinux_state struct. These helper functions use READ_ONCE and WRITE_ONCE macros to ensure atomic read or write of memory for this data member. Signed-off-by: Lakshmi Ramasubramanian Suggested-by: Stephen Smalley Suggested-by: Paul Moore Acked-by: Stephen Smalley Signed-off-by: Paul Moore

selinux: access policycaps with READ_ONCE/WRITE_ONCE

2020-09-11T14:08:51+00:00

Use READ_ONCE/WRITE_ONCE for all accesses to the selinux_state.policycaps booleans to prevent compiler mischief. Signed-off-by: Stephen Smalley Signed-off-by: Paul Moore

selinux: simplify away security_policydb_len()

2020-08-31T14:00:14+00:00

Remove the security_policydb_len() calls from sel_open_policy() and instead update the inode size from the size returned from security_read_policy(). Since after this change security_policydb_len() is only called from security_load_policy(), remove it entirely and just open-code it there. Also, since security_load_policy() is always called with policy_mutex held, make it dereference the policy pointer directly and drop the unnecessary RCU locking. Signed-off-by: Ondrej Mosnacek Acked-by: Stephen Smalley Signed-off-by: Paul Moore

selinux: move policy mutex to selinux_state, use in lockdep checks

2020-08-27T13:52:47+00:00

Move the mutex used to synchronize policy changes (reloads and setting of booleans) from selinux_fs_info to selinux_state and use it in lockdep checks for rcu_dereference_protected() calls in the security server functions. This makes the dependency on the mutex explicit in the code rather than relying on comments. Signed-off-by: Stephen Smalley Reviewed-by: Ondrej Mosnacek Signed-off-by: Paul Moore

selinux: convert policy read-write lock to RCU

2020-08-25T12:34:47+00:00

Convert the policy read-write lock to RCU. This is significantly simplified by the earlier work to encapsulate the policy data structures and refactor the policy load and boolean setting logic. Move the latest_granting sequence number into the selinux_policy structure so that it can be updated atomically with the policy. Since removing the policy rwlock and moving latest_granting reduces the selinux_ss structure to nothing more than a wrapper around the selinux_policy pointer, get rid of the extra layer of indirection. At present this change merely passes a hardcoded 1 to rcu_dereference_check() in the cases where we know we do not need to take rcu_read_lock(), with the preceding comment explaining why. Alternatively we could pass fsi->mutex down from selinuxfs and apply a lockdep check on it instead. Based in part on earlier attempts to convert the policy rwlock to RCU by Kaigai Kohei [1] and by Peter Enderborg [2]. [1] https://lore.kernel.org/selinux/6e2f9128-e191-ebb3-0e87-74bfccb0767f@tycho.nsa.gov/ [2] https://lore.kernel.org/selinux/20180530141104.28569-1-peter.enderborg@sony.com/ Signed-off-by: Stephen Smalley Reviewed-by: Ondrej Mosnacek Signed-off-by: Paul Moore

selinux: move policy commit after updating selinuxfs

2020-08-18T00:50:22+00:00

With the refactoring of the policy load logic in the security server from the previous change, it is now possible to split out the committing of the new policy from security_load_policy() and perform it only after successful updating of selinuxfs. Change security_load_policy() to return the newly populated policy data structures to the caller, export selinux_policy_commit() for external callers, and introduce selinux_policy_cancel() to provide a way to cancel the policy load in the event of an error during updating of the selinuxfs directory tree. Further, rework the interfaces used by selinuxfs to get information from the policy when creating the new directory tree to take and act upon the new policy data structure rather than the current/active policy. Update selinuxfs to use these updated and new interfaces. While we are here, stop re-creating the policy_capabilities directory on each policy load since it does not depend on the policy, and stop trying to create the booleans and classes directories during the initial creation of selinuxfs since no information is available until first policy load. After this change, a failure while updating the booleans and class directories will cause the entire policy load to be canceled, leaving the original policy intact, and policy load notifications to userspace will only happen after a successful completion of updating those directories. This does not (yet) provide full atomicity with respect to the updating of the directory trees themselves. Signed-off-by: Stephen Smalley Signed-off-by: Paul Moore

scripts/selinux,selinux: update mdp to enable policy capabilities

2020-08-18T00:42:00+00:00

Presently mdp does not enable any SELinux policy capabilities in the dummy policy it generates. Thus, policies derived from it will by default lack various features commonly used in modern policies such as open permission, extended socket classes, network peer controls, etc. Split the policy capability definitions out into their own headers so that we can include them into mdp without pulling in other kernel headers and extend mdp generate policycap statements for the policy capabilities known to the kernel. Policy authors may wish to selectively remove some of these from the generated policy. Signed-off-by: Stephen Smalley Signed-off-by: Paul Moore

capabilities: Introduce CAP_CHECKPOINT_RESTORE

2020-07-19T18:14:42+00:00

This patch introduces CAP_CHECKPOINT_RESTORE, a new capability facilitating checkpoint/restore for non-root users. Over the last years, The CRIU (Checkpoint/Restore In Userspace) team has been asked numerous times if it is possible to checkpoint/restore a process as non-root. The answer usually was: 'almost'. The main blocker to restore a process as non-root was to control the PID of the restored process. This feature available via the clone3 system call, or via /proc/sys/kernel/ns_last_pid is unfortunately guarded by CAP_SYS_ADMIN. In the past two years, requests for non-root checkpoint/restore have increased due to the following use cases: * Checkpoint/Restore in an HPC environment in combination with a resource manager distributing jobs where users are always running as non-root. There is a desire to provide a way to checkpoint and restore long running jobs. * Container migration as non-root * We have been in contact with JVM developers who are integrating CRIU into a Java VM to decrease the startup time. These checkpoint/restore applications are not meant to be running with CAP_SYS_ADMIN. We have seen the following workarounds: * Use a setuid wrapper around CRIU: See https://github.com/FredHutch/slurm-examples/blob/master/checkpointer/lib/checkpointer/checkpointer-suid.c * Use a setuid helper that writes to ns_last_pid. Unfortunately, this helper delegation technique is impossible to use with clone3, and is thus prone to races. See https://github.com/twosigma/set_ns_last_pid * Cycle through PIDs with fork() until the desired PID is reached: This has been demonstrated to work with cycling rates of 100,000 PIDs/s See https://github.com/twosigma/set_ns_last_pid * Patch out the CAP_SYS_ADMIN check from the kernel * Run the desired application in a new user and PID namespace to provide a local CAP_SYS_ADMIN for controlling PIDs. This technique has limited use in typical container environments (e.g., Kubernetes) as /proc is typically protected with read-only layers (e.g., /proc/sys) for hardening purposes. Read-only layers prevent additional /proc mounts (due to proc's SB_I_USERNS_VISIBLE property), making the use of new PID namespaces limited as certain applications need access to /proc matching their PID namespace. The introduced capability allows to: * Control PIDs when the current user is CAP_CHECKPOINT_RESTORE capable for the corresponding PID namespace via ns_last_pid/clone3. * Open files in /proc/pid/map_files when the current user is CAP_CHECKPOINT_RESTORE capable in the root namespace, useful for recovering files that are unreachable via the file system such as deleted files, or memfd files. See corresponding selftest for an example with clone3(). Signed-off-by: Adrian Reber Signed-off-by: Nicolas Viennot Reviewed-by: Serge Hallyn Acked-by: Christian Brauner Link: https://lore.kernel.org/r/20200719100418.2112740-2-areber@redhat.com Signed-off-by: Christian Brauner