linux/kernel/sys_ni.c, branch v6.8

Merge tag 'lsm-pr-20240105' of git://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/lsm

2024-01-09T20:57:46Z

Pull security module updates from Paul Moore: - Add three new syscalls: lsm_list_modules(), lsm_get_self_attr(), and lsm_set_self_attr(). The first syscall simply lists the LSMs enabled, while the second and third get and set the current process' LSM attributes. Yes, these syscalls may provide similar functionality to what can be found under /proc or /sys, but they were designed to support multiple, simultaneaous (stacked) LSMs from the start as opposed to the current /proc based solutions which were created at a time when only one LSM was allowed to be active at a given time. We have spent considerable time discussing ways to extend the existing /proc interfaces to support multiple, simultaneaous LSMs and even our best ideas have been far too ugly to support as a kernel API; after +20 years in the kernel, I felt the LSM layer had established itself enough to justify a handful of syscalls. Support amongst the individual LSM developers has been nearly unanimous, with a single objection coming from Tetsuo (TOMOYO) as he is worried that the LSM_ID_XXX token concept will make it more difficult for out-of-tree LSMs to survive. Several members of the LSM community have demonstrated the ability for out-of-tree LSMs to continue to exist by picking high/unused LSM_ID values as well as pointing out that many kernel APIs rely on integer identifiers, e.g. syscalls (!), but unfortunately Tetsuo's objections remain. My personal opinion is that while I have no interest in penalizing out-of-tree LSMs, I'm not going to penalize in-tree development to support out-of-tree development, and I view this as a necessary step forward to support the push for expanded LSM stacking and reduce our reliance on /proc and /sys which has occassionally been problematic for some container users. Finally, we have included the linux-api folks on (all?) recent revisions of the patchset and addressed all of their concerns. - Add a new security_file_ioctl_compat() LSM hook to handle the 32-bit ioctls on 64-bit systems problem. This patch includes support for all of the existing LSMs which provide ioctl hooks, although it turns out only SELinux actually cares about the individual ioctls. It is worth noting that while Casey (Smack) and Tetsuo (TOMOYO) did not give explicit ACKs to this patch, they did both indicate they are okay with the changes. - Fix a potential memory leak in the CALIPSO code when IPv6 is disabled at boot. While it's good that we are fixing this, I doubt this is something users are seeing in the wild as you need to both disable IPv6 and then attempt to configure IPv6 labeled networking via NetLabel/CALIPSO; that just doesn't make much sense. Normally this would go through netdev, but Jakub asked me to take this patch and of all the trees I maintain, the LSM tree seemed like the best fit. - Update the LSM MAINTAINERS entry with additional information about our process docs, patchwork, bug reporting, etc. I also noticed that the Lockdown LSM is missing a dedicated MAINTAINERS entry so I've added that to the pull request. I've been working with one of the major Lockdown authors/contributors to see if they are willing to step up and assume a Lockdown maintainer role; hopefully that will happen soon, but in the meantime I'll continue to look after it. - Add a handful of mailmap entries for Serge Hallyn and myself. * tag 'lsm-pr-20240105' of git://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/lsm: (27 commits) lsm: new security_file_ioctl_compat() hook lsm: Add a __counted_by() annotation to lsm_ctx.ctx calipso: fix memory leak in netlbl_calipso_add_pass() selftests: remove the LSM_ID_IMA check in lsm/lsm_list_modules_test MAINTAINERS: add an entry for the lockdown LSM MAINTAINERS: update the LSM entry mailmap: add entries for Serge Hallyn's dead accounts mailmap: update/replace my old email addresses lsm: mark the lsm_id variables are marked as static lsm: convert security_setselfattr() to use memdup_user() lsm: align based on pointer length in lsm_fill_user_ctx() lsm: consolidate buffer size handling into lsm_fill_user_ctx() lsm: correct error codes in security_getselfattr() lsm: cleanup the size counters in security_getselfattr() lsm: don't yet account for IMA in LSM_CONFIG_COUNT calculation lsm: drop LSM_ID_IMA LSM: selftests for Linux Security Module syscalls SELinux: Add selfattr hooks AppArmor: Add selfattr hooks Smack: implement setselfattr and getselfattr hooks ...

posix-timers: Get rid of [COMPAT_]SYS_NI() uses

2023-12-21T05:30:27Z

Only the posix timer system calls use this (when the posix timer support is disabled, which does not actually happen in any normal case), because they had debug code to print out a warning about missing system calls. Get rid of that special case, and just use the standard COND_SYSCALL interface that creates weak system call stubs that return -ENOSYS for when the system call does not exist. This fixes a kCFI issue with the SYS_NI() hackery: CFI failure at int80_emulation+0x67/0xb0 (target: sys_ni_posix_timers+0x0/0x70; expected type: 0xb02b34d9) WARNING: CPU: 0 PID: 48 at int80_emulation+0x67/0xb0 Reported-by: kernel test robot Reviewed-by: Sami Tolvanen Tested-by: Sami Tolvanen Cc: Thomas Gleixner Cc: Dave Hansen Cc: Borislav Petkov Signed-off-by: Linus Torvalds

LSM: Create lsm_list_modules system call

2023-11-13T03:54:42Z

Create a system call to report the list of Linux Security Modules that are active on the system. The list is provided as an array of LSM ID numbers. The calling application can use this list determine what LSM specific actions it might take. That might include choosing an output format, determining required privilege or bypassing security module specific behavior. Signed-off-by: Casey Schaufler Reviewed-by: Kees Cook Reviewed-by: Serge Hallyn Reviewed-by: John Johansen Reviewed-by: Mickaël Salaün Signed-off-by: Paul Moore

LSM: syscalls for current process attributes

2023-11-13T03:54:42Z

Create a system call lsm_get_self_attr() to provide the security module maintained attributes of the current process. Create a system call lsm_set_self_attr() to set a security module maintained attribute of the current process. Historically these attributes have been exposed to user space via entries in procfs under /proc/self/attr. The attribute value is provided in a lsm_ctx structure. The structure identifies the size of the attribute, and the attribute value. The format of the attribute value is defined by the security module. A flags field is included for LSM specific information. It is currently unused and must be 0. The total size of the data, including the lsm_ctx structure and any padding, is maintained as well. struct lsm_ctx { __u64 id; __u64 flags; __u64 len; __u64 ctx_len; __u8 ctx[]; }; Two new LSM hooks are used to interface with the LSMs. security_getselfattr() collects the lsm_ctx values from the LSMs that support the hook, accounting for space requirements. security_setselfattr() identifies which LSM the attribute is intended for and passes it along. Signed-off-by: Casey Schaufler Reviewed-by: Kees Cook Reviewed-by: Serge Hallyn Reviewed-by: John Johansen Signed-off-by: Paul Moore

Merge tag 'asm-generic-6.7' of git://git.kernel.org/pub/scm/linux/kernel/git/arnd/asm-generic

2023-11-02T01:28:33Z

Pull ia64 removal and asm-generic updates from Arnd Bergmann: - The ia64 architecture gets its well-earned retirement as planned, now that there is one last (mostly) working release that will be maintained as an LTS kernel. - The architecture specific system call tables are updated for the added map_shadow_stack() syscall and to remove references to the long-gone sys_lookup_dcookie() syscall. * tag 'asm-generic-6.7' of git://git.kernel.org/pub/scm/linux/kernel/git/arnd/asm-generic: hexagon: Remove unusable symbols from the ptrace.h uapi asm-generic: Fix spelling of architecture arch: Reserve map_shadow_stack() syscall number for all architectures syscalls: Cleanup references to sys_lookup_dcookie() Documentation: Drop or replace remaining mentions of IA64 lib/raid6: Drop IA64 support Documentation: Drop IA64 from feature descriptions kernel: Drop IA64 support from sig_fault handlers arch: Remove Itanium (IA-64) architecture

syscalls: Cleanup references to sys_lookup_dcookie()

2023-10-03T17:51:37Z

commit 'be65de6b03aa ("fs: Remove dcookies support")' removed the syscall definition for lookup_dcookie. However, syscall tables still point to the old sys_lookup_dcookie() definition. Update syscall tables of all architectures to directly point to sys_ni_syscall() instead. Signed-off-by: Sohil Mehta Reviewed-by: Randy Dunlap Acked-by: Namhyung Kim # for perf Acked-by: Russell King (Oracle) Acked-by: Geert Uytterhoeven Signed-off-by: Arnd Bergmann

futex: Add sys_futex_requeue()

2023-09-21T17:22:10Z

Finish off the 'simple' futex2 syscall group by adding sys_futex_requeue(). Unlike sys_futex_{wait,wake}() its arguments are too numerous to fit into a regular syscall. As such, use struct futex_waitv to pass the 'source' and 'destination' futexes to the syscall. This syscall implements what was previously known as FUTEX_CMP_REQUEUE and uses {val, uaddr, flags} for source and {uaddr, flags} for destination. This design explicitly allows requeueing between different types of futex by having a different flags word per uaddr. Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Thomas Gleixner Acked-by: Geert Uytterhoeven Link: https://lore.kernel.org/r/20230921105248.511860556@noisy.programming.kicks-ass.net

futex: Add sys_futex_wait()

2023-09-21T17:22:08Z

To complement sys_futex_waitv()/wake(), add sys_futex_wait(). This syscall implements what was previously known as FUTEX_WAIT_BITSET except it uses 'unsigned long' for the value and bitmask arguments, takes timespec and clockid_t arguments for the absolute timeout and uses FUTEX2 flags. The 'unsigned long' allows FUTEX2_SIZE_U64 on 64bit platforms. Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Thomas Gleixner Acked-by: Geert Uytterhoeven Link: https://lore.kernel.org/r/20230921105248.164324363@noisy.programming.kicks-ass.net

futex: Add sys_futex_wake()

2023-09-21T17:22:07Z

To complement sys_futex_waitv() add sys_futex_wake(). This syscall implements what was previously known as FUTEX_WAKE_BITSET except it uses 'unsigned long' for the bitmask and takes FUTEX2 flags. The 'unsigned long' allows FUTEX2_SIZE_U64 on 64bit platforms. Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Thomas Gleixner Acked-by: Geert Uytterhoeven Link: https://lore.kernel.org/r/20230921105247.936205525@noisy.programming.kicks-ass.net

x86/shstk: Introduce map_shadow_stack syscall

2023-08-02T22:01:51Z

When operating with shadow stacks enabled, the kernel will automatically allocate shadow stacks for new threads, however in some cases userspace will need additional shadow stacks. The main example of this is the ucontext family of functions, which require userspace allocating and pivoting to userspace managed stacks. Unlike most other user memory permissions, shadow stacks need to be provisioned with special data in order to be useful. They need to be setup with a restore token so that userspace can pivot to them via the RSTORSSP instruction. But, the security design of shadow stacks is that they should not be written to except in limited circumstances. This presents a problem for userspace, as to how userspace can provision this special data, without allowing for the shadow stack to be generally writable. Previously, a new PROT_SHADOW_STACK was attempted, which could be mprotect()ed from RW permissions after the data was provisioned. This was found to not be secure enough, as other threads could write to the shadow stack during the writable window. The kernel can use a special instruction, WRUSS, to write directly to userspace shadow stacks. So the solution can be that memory can be mapped as shadow stack permissions from the beginning (never generally writable in userspace), and the kernel itself can write the restore token. First, a new madvise() flag was explored, which could operate on the PROT_SHADOW_STACK memory. This had a couple of downsides: 1. Extra checks were needed in mprotect() to prevent writable memory from ever becoming PROT_SHADOW_STACK. 2. Extra checks/vma state were needed in the new madvise() to prevent restore tokens being written into the middle of pre-used shadow stacks. It is ideal to prevent restore tokens being added at arbitrary locations, so the check was to make sure the shadow stack had never been written to. 3. It stood out from the rest of the madvise flags, as more of direct action than a hint at future desired behavior. So rather than repurpose two existing syscalls (mmap, madvise) that don't quite fit, just implement a new map_shadow_stack syscall to allow userspace to map and setup new shadow stacks in one step. While ucontext is the primary motivator, userspace may have other unforeseen reasons to setup its own shadow stacks using the WRSS instruction. Towards this provide a flag so that stacks can be optionally setup securely for the common case of ucontext without enabling WRSS. Or potentially have the kernel set up the shadow stack in some new way. The following example demonstrates how to create a new shadow stack with map_shadow_stack: void *shstk = map_shadow_stack(addr, stack_size, SHADOW_STACK_SET_TOKEN); Signed-off-by: Rick Edgecombe Signed-off-by: Dave Hansen Reviewed-by: Borislav Petkov (AMD) Reviewed-by: Kees Cook Acked-by: Mike Rapoport (IBM) Tested-by: Pengfei Xu Tested-by: John Allen Tested-by: Kees Cook Link: https://lore.kernel.org/all/20230613001108.3040476-35-rick.p.edgecombe%40intel.com