kernel/linux.git/security/Kconfig, branch v6.18.21

lsm: CONFIG_LSM can depend on CONFIG_SECURITY

2025-09-11T20:32:04+00:00

When CONFIG_SECURITY is not set, CONFIG_LSM (builtin_lsm_order) does not need to be visible and settable since builtin_lsm_order is defined in security.o, which is only built when CONFIG_SECURITY=y. So make CONFIG_LSM depend on CONFIG_SECURITY. Fixes: 13e735c0e953 ("LSM: Introduce CONFIG_LSM") Signed-off-by: Randy Dunlap [PM: subj tweak] Signed-off-by: Paul Moore

mseal sysmap: kernel config and header change

2025-04-01T22:17:14+00:00

Patch series "mseal system mappings", v9. As discussed during mseal() upstream process [1], mseal() protects the VMAs of a given virtual memory range against modifications, such as the read/write (RW) and no-execute (NX) bits. For complete descriptions of memory sealing, please see mseal.rst [2]. The mseal() is useful to mitigate memory corruption issues where a corrupted pointer is passed to a memory management system. For example, such an attacker primitive can break control-flow integrity guarantees since read-only memory that is supposed to be trusted can become writable or .text pages can get remapped. The system mappings are readonly only, memory sealing can protect them from ever changing to writable or unmmap/remapped as different attributes. System mappings such as vdso, vvar, vvar_vclock, vectors (arm compat-mode), sigpage (arm compat-mode), are created by the kernel during program initialization, and could be sealed after creation. Unlike the aforementioned mappings, the uprobe mapping is not established during program startup. However, its lifetime is the same as the process's lifetime [3]. It could be sealed from creation. The vsyscall on x86-64 uses a special address (0xffffffffff600000), which is outside the mm managed range. This means mprotect, munmap, and mremap won't work on the vsyscall. Since sealing doesn't enhance the vsyscall's security, it is skipped in this patch. If we ever seal the vsyscall, it is probably only for decorative purpose, i.e. showing the 'sl' flag in the /proc/pid/smaps. For this patch, it is ignored. It is important to note that the CHECKPOINT_RESTORE feature (CRIU) may alter the system mappings during restore operations. UML(User Mode Linux) and gVisor, rr are also known to change the vdso/vvar mappings. Consequently, this feature cannot be universally enabled across all systems. As such, CONFIG_MSEAL_SYSTEM_MAPPINGS is disabled by default. To support mseal of system mappings, architectures must define CONFIG_ARCH_SUPPORTS_MSEAL_SYSTEM_MAPPINGS and update their special mappings calls to pass mseal flag. Additionally, architectures must confirm they do not unmap/remap system mappings during the process lifetime. The existence of this flag for an architecture implies that it does not require the remapping of thest system mappings during process lifetime, so sealing these mappings is safe from a kernel perspective. This version covers x86-64 and arm64 archiecture as minimum viable feature. While no specific CPU hardware features are required for enable this feature on an archiecture, memory sealing requires a 64-bit kernel. Other architectures can choose whether or not to adopt this feature. Currently, I'm not aware of any instances in the kernel code that actively munmap/mremap a system mapping without a request from userspace. The PPC does call munmap when _install_special_mapping fails for vdso; however, it's uncertain if this will ever fail for PPC - this needs to be investigated by PPC in the future [4]. The UML kernel can add this support when KUnit tests require it [5]. In this version, we've improved the handling of system mapping sealing from previous versions, instead of modifying the _install_special_mapping function itself, which would affect all architectures, we now call _install_special_mapping with a sealing flag only within the specific architecture that requires it. This targeted approach offers two key advantages: 1) It limits the code change's impact to the necessary architectures, and 2) It aligns with the software architecture by keeping the core memory management within the mm layer, while delegating the decision of sealing system mappings to the individual architecture, which is particularly relevant since 32-bit architectures never require sealing. Prior to this patch series, we explored sealing special mappings from userspace using glibc's dynamic linker. This approach revealed several issues: - The PT_LOAD header may report an incorrect length for vdso, (smaller than its actual size). The dynamic linker, which relies on PT_LOAD information to determine mapping size, would then split and partially seal the vdso mapping. Since each architecture has its own vdso/vvar code, fixing this in the kernel would require going through each archiecture. Our initial goal was to enable sealing readonly mappings, e.g. .text, across all architectures, sealing vdso from kernel since creation appears to be simpler than sealing vdso at glibc. - The [vvar] mapping header only contains address information, not length information. Similar issues might exist for other special mappings. - Mappings like uprobe are not covered by the dynamic linker, and there is no effective solution for them. This feature's security enhancements will benefit ChromeOS, Android, and other high security systems. Testing: This feature was tested on ChromeOS and Android for both x86-64 and ARM64. - Enable sealing and verify vdso/vvar, sigpage, vector are sealed properly, i.e. "sl" shown in the smaps for those mappings, and mremap is blocked. - Passing various automation tests (e.g. pre-checkin) on ChromeOS and Android to ensure the sealing doesn't affect the functionality of Chromebook and Android phone. I also tested the feature on Ubuntu on x86-64: - With config disabled, vdso/vvar is not sealed, - with config enabled, vdso/vvar is sealed, and booting up Ubuntu is OK, normal operations such as browsing the web, open/edit doc are OK. Link: https://lore.kernel.org/all/20240415163527.626541-1-jeffxu@chromium.org/ [1] Link: Documentation/userspace-api/mseal.rst [2] Link: https://lore.kernel.org/all/CABi2SkU9BRUnqf70-nksuMCQ+yyiWjo3fM4XkRkL-NrCZxYAyg@mail.gmail.com/ [3] Link: https://lore.kernel.org/all/CABi2SkV6JJwJeviDLsq9N4ONvQ=EFANsiWkgiEOjyT9TQSt+HA@mail.gmail.com/ [4] Link: https://lore.kernel.org/all/202502251035.239B85A93@keescook/ [5] This patch (of 7): Provide infrastructure to mseal system mappings. Establish two kernel configs (CONFIG_MSEAL_SYSTEM_MAPPINGS, ARCH_SUPPORTS_MSEAL_SYSTEM_MAPPINGS) and VM_SEALED_SYSMAP macro for future patches. Link: https://lkml.kernel.org/r/20250305021711.3867874-1-jeffxu@google.com Link: https://lkml.kernel.org/r/20250305021711.3867874-2-jeffxu@google.com Signed-off-by: Jeff Xu Reviewed-by: Kees Cook Reviewed-by: Liam R. Howlett Reviewed-by: Lorenzo Stoakes Cc: Adhemerval Zanella Cc: Alexander Mikhalitsyn Cc: Alexey Dobriyan Cc: Andrei Vagin Cc: Anna-Maria Behnsen Cc: Ard Biesheuvel Cc: Benjamin Berg Cc: Christoph Hellwig Cc: Dave Hansen Cc: David Rientjes Cc: David S. Miller Cc: Elliot Hughes Cc: Florian Faineli Cc: Greg Ungerer Cc: Guenter Roeck Cc: Heiko Carstens Cc: Helge Deller Cc: Hyeonggon Yoo <42.hyeyoo@gmail.com> Cc: Ingo Molnar Cc: Jann Horn Cc: Jason A. Donenfeld Cc: Johannes Berg Cc: Jorge Lucangeli Obes Cc: Linus Waleij Cc: Mark Rutland Cc: Matthew Wilcow (Oracle) Cc: Michael Ellerman Cc: Michal Hocko Cc: Miguel Ojeda Cc: Mike Rapoport Cc: Oleg Nesterov Cc: Pedro Falcato Cc: Peter Xu Cc: Randy Dunlap Cc: Stephen Röttger Cc: Thomas Weißschuh Cc: Vlastimil Babka Signed-off-by: Andrew Morton

fortify: Move FORTIFY_SOURCE under 'Kernel hardening options'

2025-02-28T19:51:31+00:00

FORTIFY_SOURCE is a hardening option both at build and runtime. Move it under 'Kernel hardening options'. Signed-off-by: Mel Gorman Acked-by: Paul Moore Link: https://lore.kernel.org/r/20250123221115.19722-5-mgorman@techsingularity.net Signed-off-by: Kees Cook

mm: security: Move hardened usercopy under 'Kernel hardening options'

2025-02-28T19:51:31+00:00

There is a submenu for 'Kernel hardening options' under "Security". Move HARDENED_USERCOPY under the hardening options as it is clearly related. Signed-off-by: Mel Gorman Acked-by: Paul Moore Link: https://lore.kernel.org/r/20250123221115.19722-2-mgorman@techsingularity.net Signed-off-by: Kees Cook

lsm: Only build lsm_audit.c if CONFIG_SECURITY and CONFIG_AUDIT are set

2025-01-04T16:50:44+00:00

When CONFIG_AUDIT is set, its CONFIG_NET dependency is also set, and the dev_get_by_index and init_net symbols (used by dump_common_audit_data) are found by the linker. dump_common_audit_data() should then failed to build when CONFIG_NET is not set. However, because the compiler is smart, it knows that audit_log_start() always return NULL when !CONFIG_AUDIT, and it doesn't build the body of common_lsm_audit(). As a side effect, dump_common_audit_data() is not built and the linker doesn't error out because of missing symbols. Let's only build lsm_audit.o when CONFIG_SECURITY and CONFIG_AUDIT are both set, which is checked with the new CONFIG_HAS_SECURITY_AUDIT. ipv4_skb_to_auditdata() and ipv6_skb_to_auditdata() are only used by Smack if CONFIG_AUDIT is set, so they don't need fake implementations. Because common_lsm_audit() is used in multiple places without CONFIG_AUDIT checks, add a fake implementation. Link: https://lore.kernel.org/r/20241122143353.59367-2-mic@digikod.net Cc: Casey Schaufler Cc: James Morris Cc: Paul Moore Cc: Serge E. Hallyn Signed-off-by: Mickaël Salaün Signed-off-by: Paul Moore

Merge tag 'lsm-pr-20240911' of git://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/lsm

2024-09-16T16:19:47+00:00

Pull lsm updates from Paul Moore: - Move the LSM framework to static calls This transitions the vast majority of the LSM callbacks into static calls. Those callbacks which haven't been converted were left as-is due to the general ugliness of the changes required to support the static call conversion; we can revisit those callbacks at a future date. - Add the Integrity Policy Enforcement (IPE) LSM This adds a new LSM, Integrity Policy Enforcement (IPE). There is plenty of documentation about IPE in this patches, so I'll refrain from going into too much detail here, but the basic motivation behind IPE is to provide a mechanism such that administrators can restrict execution to only those binaries which come from integrity protected storage, e.g. a dm-verity protected filesystem. You will notice that IPE requires additional LSM hooks in the initramfs, dm-verity, and fs-verity code, with the associated patches carrying ACK/review tags from the associated maintainers. We couldn't find an obvious maintainer for the initramfs code, but the IPE patchset has been widely posted over several years. Both Deven Bowers and Fan Wu have contributed to IPE's development over the past several years, with Fan Wu agreeing to serve as the IPE maintainer moving forward. Once IPE is accepted into your tree, I'll start working with Fan to ensure he has the necessary accounts, keys, etc. so that he can start submitting IPE pull requests to you directly during the next merge window. - Move the lifecycle management of the LSM blobs to the LSM framework Management of the LSM blobs (the LSM state buffers attached to various kernel structs, typically via a void pointer named "security" or similar) has been mixed, some blobs were allocated/managed by individual LSMs, others were managed by the LSM framework itself. Starting with this pull we move management of all the LSM blobs, minus the XFRM blob, into the framework itself, improving consistency across LSMs, and reducing the amount of duplicated code across LSMs. Due to some additional work required to migrate the XFRM blob, it has been left as a todo item for a later date; from a practical standpoint this omission should have little impact as only SELinux provides a XFRM LSM implementation. - Fix problems with the LSM's handling of F_SETOWN The LSM hook for the fcntl(F_SETOWN) operation had a couple of problems: it was racy with itself, and it was disconnected from the associated DAC related logic in such a way that the LSM state could be updated in cases where the DAC state would not. We fix both of these problems by moving the security_file_set_fowner() hook into the same section of code where the DAC attributes are updated. Not only does this resolve the DAC/LSM synchronization issue, but as that code block is protected by a lock, it also resolve the race condition. - Fix potential problems with the security_inode_free() LSM hook Due to use of RCU to protect inodes and the placement of the LSM hook associated with freeing the inode, there is a bit of a challenge when it comes to managing any LSM state associated with an inode. The VFS folks are not open to relocating the LSM hook so we have to get creative when it comes to releasing an inode's LSM state. Traditionally we have used a single LSM callback within the hook that is triggered when the inode is "marked for death", but not actually released due to RCU. Unfortunately, this causes problems for LSMs which want to take an action when the inode's associated LSM state is actually released; so we add an additional LSM callback, inode_free_security_rcu(), that is called when the inode's LSM state is released in the RCU free callback. - Refactor two LSM hooks to better fit the LSM return value patterns The vast majority of the LSM hooks follow the "return 0 on success, negative values on failure" pattern, however, there are a small handful that have unique return value behaviors which has caused confusion in the past and makes it difficult for the BPF verifier to properly vet BPF LSM programs. This includes patches to convert two of these"special" LSM hooks to the common 0/-ERRNO pattern. - Various cleanups and improvements A handful of patches to remove redundant code, better leverage the IS_ERR_OR_NULL() helper, add missing "static" markings, and do some minor style fixups. * tag 'lsm-pr-20240911' of git://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/lsm: (40 commits) security: Update file_set_fowner documentation fs: Fix file_set_fowner LSM hook inconsistencies lsm: Use IS_ERR_OR_NULL() helper function lsm: remove LSM_COUNT and LSM_CONFIG_COUNT ipe: Remove duplicated include in ipe.c lsm: replace indirect LSM hook calls with static calls lsm: count the LSMs enabled at compile time kernel: Add helper macros for loop unrolling init/main.c: Initialize early LSMs after arch code, static keys and calls. MAINTAINERS: add IPE entry with Fan Wu as maintainer documentation: add IPE documentation ipe: kunit test for parser scripts: add boot policy generation program ipe: enable support for fs-verity as a trust provider fsverity: expose verified fsverity built-in signatures to LSMs lsm: add security_inode_setintegrity() hook ipe: add support for dm-verity as a trust provider dm-verity: expose root hash digest and signature data to LSMs block,lsm: add LSM blob and new LSM hooks for block devices ipe: add permissive toggle ...

proc: add config & param to block forcing mem writes

2024-08-30T06:19:43+00:00

This adds a Kconfig option and boot param to allow removing the FOLL_FORCE flag from /proc/pid/mem write calls because it can be abused. The traditional forcing behavior is kept as default because it can break GDB and some other use cases. Previously we tried a more sophisticated approach allowing distributions to fine-tune /proc/pid/mem behavior, however that got NAK-ed by Linus [1], who prefers this simpler approach with semantics also easier to understand for users. Link: https://lore.kernel.org/lkml/CAHk-=wiGWLChxYmUA5HrT5aopZrB7_2VTa0NLZcxORgkUe5tEQ@mail.gmail.com/ [1] Cc: Doug Anderson Cc: Jeff Xu Cc: Jann Horn Cc: Kees Cook Cc: Ard Biesheuvel Cc: Christian Brauner Suggested-by: Linus Torvalds Signed-off-by: Linus Torvalds Signed-off-by: Adrian Ratiu Link: https://lore.kernel.org/r/20240802080225.89408-1-adrian.ratiu@collabora.com Signed-off-by: Christian Brauner

lsm: add IPE lsm

2024-08-20T02:36:26+00:00

Integrity Policy Enforcement (IPE) is an LSM that provides an complimentary approach to Mandatory Access Control than existing LSMs today. Existing LSMs have centered around the concept of access to a resource should be controlled by the current user's credentials. IPE's approach, is that access to a resource should be controlled by the system's trust of a current resource. The basis of this approach is defining a global policy to specify which resource can be trusted. Signed-off-by: Deven Bowers Signed-off-by: Fan Wu [PM: subject line tweak] Signed-off-by: Paul Moore

fortify: drop Clang version check for 12.0.1 or newer

2024-02-22T23:38:54+00:00

Now that the minimum supported version of LLVM for building the kernel has been bumped to 13.0.1, this condition is always true, as the build will fail during the configuration stage for older LLVM versions. Remove it. Link: https://lkml.kernel.org/r/20240125-bump-min-llvm-ver-to-13-0-1-v1-9-f5ff9bda41c5@kernel.org Signed-off-by: Nathan Chancellor Reviewed-by: Kees Cook Cc: Albert Ou Cc: "Aneesh Kumar K.V (IBM)" Cc: Ard Biesheuvel Cc: Borislav Petkov (AMD) Cc: Catalin Marinas Cc: Conor Dooley Cc: Dave Hansen Cc: Ingo Molnar Cc: Mark Rutland Cc: Masahiro Yamada Cc: Michael Ellerman Cc: "Naveen N. Rao" Cc: Nicholas Piggin Cc: Nicolas Schier Cc: Palmer Dabbelt Cc: Paul Walmsley Cc: Russell King Cc: Thomas Gleixner Cc: Will Deacon Signed-off-by: Andrew Morton

treewide: update LLVM Bugzilla links

2024-02-22T23:38:51+00:00

LLVM moved their issue tracker from their own Bugzilla instance to GitHub issues. While all of the links are still valid, they may not necessarily show the most up to date information around the issues, as all updates will occur on GitHub, not Bugzilla. Another complication is that the Bugzilla issue number is not always the same as the GitHub issue number. Thankfully, LLVM maintains this mapping through two shortlinks: https://llvm.org/bz -> https://bugs.llvm.org/show_bug.cgi?id= https://llvm.org/pr -> https://github.com/llvm/llvm-project/issues/ Switch all "https://bugs.llvm.org/show_bug.cgi?id=" links to the "https://llvm.org/pr" shortlink so that the links show the most up to date information. Each migrated issue links back to the Bugzilla entry, so there should be no loss of fidelity of information here. Link: https://lkml.kernel.org/r/20240109-update-llvm-links-v1-3-eb09b59db071@kernel.org Signed-off-by: Nathan Chancellor Reviewed-by: Kees Cook Acked-by: Fangrui Song Cc: Alexei Starovoitov Cc: Andrii Nakryiko Cc: Daniel Borkmann Cc: Mykola Lysenko Signed-off-by: Andrew Morton