pm24.git/security/Kconfig.hardening, branch master

hardening: Adjust dependencies in selection of MODVERSIONS

2024-09-28T20:56:03Z

MODVERSIONS recently grew a dependency on !COMPILE_TEST so that Rust could be more easily tested. However, this introduces a Kconfig warning when building allmodconfig with a clang version that supports RANDSTRUCT natively because RANDSTRUCT_FULL and RANDSTRUCT_PERFORMANCE select MODVERSIONS when MODULES is enabled, bypassing the !COMPILE_TEST dependency: WARNING: unmet direct dependencies detected for MODVERSIONS Depends on [n]: MODULES [=y] && !COMPILE_TEST [=y] Selected by [y]: - RANDSTRUCT_FULL [=y] && (CC_HAS_RANDSTRUCT [=y] || GCC_PLUGINS [=n]) && MODULES [=y] Add the !COMPILE_TEST dependency to the selections to clear up the warning. Fixes: 1f9c4a996756 ("Kbuild: make MODVERSIONS support depend on not being a compile test build") Signed-off-by: Nathan Chancellor Link: https://lore.kernel.org/r/20240928-fix-randstruct-modversions-kconfig-warning-v1-1-27d3edc8571e@kernel.org Signed-off-by: Kees Cook

Revert "mm: init_mlocked_on_free_v3"

2024-06-15T17:43:05Z

There was insufficient review and no agreement that this is the right approach. There are serious flaws with the implementation that make processes using mlock() not even work with simple fork() [1] and we get reliable crashes when rebooting. Further, simply because we might be unmapping a single PTE of a large mlocked folio, we shouldn't zero out the whole folio. ... especially because the code can also *corrupt* urelated memory because kernel_init_pages(page, folio_nr_pages(folio)); Could end up writing outside of the actual folio if we work with a tail page. Let's revert it. Once there is agreement that this is the right approach, the issues were fixed and there was reasonable review and proper testing, we can consider it again. [1] https://lkml.kernel.org/r/4da9da2f-73e4-45fd-b62f-a8a513314057@redhat.com Link: https://lkml.kernel.org/r/20240605091710.38961-1-david@redhat.com Fixes: ba42b524a040 ("mm: init_mlocked_on_free_v3") Signed-off-by: David Hildenbrand Reported-by: David Wang <00107082@163.com> Closes: https://lore.kernel.org/lkml/20240528151340.4282-1-00107082@163.com/ Reported-by: Lance Yang Closes: https://lkml.kernel.org/r/20240601140917.43562-1-ioworker0@gmail.com Acked-by: Lance Yang Cc: York Jasper Niebuhr Cc: Matthew Wilcox (Oracle) Cc: Kees Cook Signed-off-by: Andrew Morton

mm: init_mlocked_on_free_v3

2024-04-26T03:56:29Z

Implements the "init_mlocked_on_free" boot option. When this boot option is enabled, any mlock'ed pages are zeroed on free. If the pages are munlock'ed beforehand, no initialization takes place. This boot option is meant to combat the performance hit of "init_on_free" as reported in commit 6471384af2a6 ("mm: security: introduce init_on_alloc=1 and init_on_free=1 boot options"). With "init_mlocked_on_free=1" only relevant data is freed while everything else is left untouched by the kernel. Correspondingly, this patch introduces no performance hit for unmapping non-mlock'ed memory. The unmapping overhead for purely mlocked memory was measured to be approximately 13%. Realistically, most systems mlock only a fraction of the total memory so the real-world system overhead should be close to zero. Optimally, userspace programs clear any key material or other confidential memory before exit and munlock the according memory regions. If a program crashes, userspace key managers fail to do this job. Accordingly, no munlock operations are performed so the data is caught and zeroed by the kernel. Should the program not crash, all memory will ideally be munlocked so no overhead is caused. CONFIG_INIT_MLOCKED_ON_FREE_DEFAULT_ON can be set to enable "init_mlocked_on_free" by default. Link: https://lkml.kernel.org/r/20240329145605.149917-1-yjnworkstation@gmail.com Signed-off-by: York Jasper Niebuhr Cc: Matthew Wilcox (Oracle) Cc: York Jasper Niebuhr Cc: Kees Cook Signed-off-by: Andrew Morton

hardening: Move BUG_ON_DATA_CORRUPTION to hardening options

2023-08-15T21:57:25Z

BUG_ON_DATA_CORRUPTION is turning detected corruptions of list data structures from WARNings into BUGs. This can be useful to stop further corruptions or even exploitation attempts. However, the option has less to do with debugging than with hardening. With the introduction of LIST_HARDENED, it makes more sense to move it to the hardening options, where it selects LIST_HARDENED instead. Without this change, combining BUG_ON_DATA_CORRUPTION with LIST_HARDENED alone wouldn't be possible, because DEBUG_LIST would always be selected by BUG_ON_DATA_CORRUPTION. Signed-off-by: Marco Elver Link: https://lore.kernel.org/r/20230811151847.1594958-4-elver@google.com Signed-off-by: Kees Cook

list: Introduce CONFIG_LIST_HARDENED

2023-08-15T21:57:25Z

Numerous production kernel configs (see [1, 2]) are choosing to enable CONFIG_DEBUG_LIST, which is also being recommended by KSPP for hardened configs [3]. The motivation behind this is that the option can be used as a security hardening feature (e.g. CVE-2019-2215 and CVE-2019-2025 are mitigated by the option [4]). The feature has never been designed with performance in mind, yet common list manipulation is happening across hot paths all over the kernel. Introduce CONFIG_LIST_HARDENED, which performs list pointer checking inline, and only upon list corruption calls the reporting slow path. To generate optimal machine code with CONFIG_LIST_HARDENED: 1. Elide checking for pointer values which upon dereference would result in an immediate access fault (i.e. minimal hardening checks). The trade-off is lower-quality error reports. 2. Use the __preserve_most function attribute (available with Clang, but not yet with GCC) to minimize the code footprint for calling the reporting slow path. As a result, function size of callers is reduced by avoiding saving registers before calling the rarely called reporting slow path. Note that all TUs in lib/Makefile already disable function tracing, including list_debug.c, and __preserve_most's implied notrace has no effect in this case. 3. Because the inline checks are a subset of the full set of checks in __list_*_valid_or_report(), always return false if the inline checks failed. This avoids redundant compare and conditional branch right after return from the slow path. As a side-effect of the checks being inline, if the compiler can prove some condition to always be true, it can completely elide some checks. Since DEBUG_LIST is functionally a superset of LIST_HARDENED, the Kconfig variables are changed to reflect that: DEBUG_LIST selects LIST_HARDENED, whereas LIST_HARDENED itself has no dependency on DEBUG_LIST. Running netperf with CONFIG_LIST_HARDENED (using a Clang compiler with "preserve_most") shows throughput improvements, in my case of ~7% on average (up to 20-30% on some test cases). Link: https://r.android.com/1266735 [1] Link: https://gitlab.archlinux.org/archlinux/packaging/packages/linux/-/blob/main/config [2] Link: https://kernsec.org/wiki/index.php/Kernel_Self_Protection_Project/Recommended_Settings [3] Link: https://googleprojectzero.blogspot.com/2019/11/bad-binder-android-in-wild-exploit.html [4] Signed-off-by: Marco Elver Link: https://lore.kernel.org/r/20230811151847.1594958-3-elver@google.com Signed-off-by: Kees Cook

randstruct: disable Clang 15 support

2023-02-08T23:26:58Z

The randstruct support released in Clang 15 is unsafe to use due to a bug that can cause miscompilations: "-frandomize-layout-seed inconsistently randomizes all-function-pointers structs" (https://github.com/llvm/llvm-project/issues/60349). It has been fixed on the Clang 16 release branch, so add a Clang version check. Fixes: 035f7f87b729 ("randstruct: Enable Clang support") Cc: stable@vger.kernel.org Signed-off-by: Eric Biggers Acked-by: Nick Desaulniers Reviewed-by: Nathan Chancellor Reviewed-by: Bill Wendling Signed-off-by: Kees Cook Link: https://lore.kernel.org/r/20230208065133.220589-1-ebiggers@kernel.org

security: Restrict CONFIG_ZERO_CALL_USED_REGS to gcc or clang > 15.0.6

2022-12-15T00:05:36Z

A bad bug in clang's implementation of -fzero-call-used-regs can result in NULL pointer dereferences (see the links above the check for more information). Restrict CONFIG_CC_HAS_ZERO_CALL_USED_REGS to either a supported GCC version or a clang newer than 15.0.6, which will catch both a theoretical 15.0.7 and the upcoming 16.0.0, which will both have the bug fixed. Cc: stable@vger.kernel.org # v5.15+ Signed-off-by: Nathan Chancellor Signed-off-by: Kees Cook Link: https://lore.kernel.org/r/20221214232602.4118147-1-nathan@kernel.org

Merge tag 'mm-stable-2022-10-08' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

2022-10-11T00:53:04Z

Pull MM updates from Andrew Morton: - Yu Zhao's Multi-Gen LRU patches are here. They've been under test in linux-next for a couple of months without, to my knowledge, any negative reports (or any positive ones, come to that). - Also the Maple Tree from Liam Howlett. An overlapping range-based tree for vmas. It it apparently slightly more efficient in its own right, but is mainly targeted at enabling work to reduce mmap_lock contention. Liam has identified a number of other tree users in the kernel which could be beneficially onverted to mapletrees. Yu Zhao has identified a hard-to-hit but "easy to fix" lockdep splat at [1]. This has yet to be addressed due to Liam's unfortunately timed vacation. He is now back and we'll get this fixed up. - Dmitry Vyukov introduces KMSAN: the Kernel Memory Sanitizer. It uses clang-generated instrumentation to detect used-unintialized bugs down to the single bit level. KMSAN keeps finding bugs. New ones, as well as the legacy ones. - Yang Shi adds a userspace mechanism (madvise) to induce a collapse of memory into THPs. - Zach O'Keefe has expanded Yang Shi's madvise(MADV_COLLAPSE) to support file/shmem-backed pages. - userfaultfd updates from Axel Rasmussen - zsmalloc cleanups from Alexey Romanov - cleanups from Miaohe Lin: vmscan, hugetlb_cgroup, hugetlb and memory-failure - Huang Ying adds enhancements to NUMA balancing memory tiering mode's page promotion, with a new way of detecting hot pages. - memcg updates from Shakeel Butt: charging optimizations and reduced memory consumption. - memcg cleanups from Kairui Song. - memcg fixes and cleanups from Johannes Weiner. - Vishal Moola provides more folio conversions - Zhang Yi removed ll_rw_block() :( - migration enhancements from Peter Xu - migration error-path bugfixes from Huang Ying - Aneesh Kumar added ability for a device driver to alter the memory tiering promotion paths. For optimizations by PMEM drivers, DRM drivers, etc. - vma merging improvements from Jakub Matěn. - NUMA hinting cleanups from David Hildenbrand. - xu xin added aditional userspace visibility into KSM merging activity. - THP & KSM code consolidation from Qi Zheng. - more folio work from Matthew Wilcox. - KASAN updates from Andrey Konovalov. - DAMON cleanups from Kaixu Xia. - DAMON work from SeongJae Park: fixes, cleanups. - hugetlb sysfs cleanups from Muchun Song. - Mike Kravetz fixes locking issues in hugetlbfs and in hugetlb core. Link: https://lkml.kernel.org/r/CAOUHufZabH85CeUN-MEMgL8gJGzJEWUrkiM58JkTbBhh-jew0Q@mail.gmail.com [1] * tag 'mm-stable-2022-10-08' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (555 commits) hugetlb: allocate vma lock for all sharable vmas hugetlb: take hugetlb vma_lock when clearing vma_lock->vma pointer hugetlb: fix vma lock handling during split vma and range unmapping mglru: mm/vmscan.c: fix imprecise comments mm/mglru: don't sync disk for each aging cycle mm: memcontrol: drop dead CONFIG_MEMCG_SWAP config symbol mm: memcontrol: use do_memsw_account() in a few more places mm: memcontrol: deprecate swapaccounting=0 mode mm: memcontrol: don't allocate cgroup swap arrays when memcg is disabled mm/secretmem: remove reduntant return value mm/hugetlb: add available_huge_pages() func mm: remove unused inline functions from include/linux/mm_inline.h selftests/vm: add selftest for MADV_COLLAPSE of uffd-minor memory selftests/vm: add file/shmem MADV_COLLAPSE selftest for cleared pmd selftests/vm: add thp collapse shmem testing selftests/vm: add thp collapse file and tmpfs testing selftests/vm: modularize thp collapse memory operations selftests/vm: dedup THP helpers mm/khugepaged: add tracepoint to hpage_collapse_scan_file() mm/madvise: add file and shmem support to MADV_COLLAPSE ...

security: kmsan: fix interoperability with auto-initialization

2022-10-03T21:03:23Z

Heap and stack initialization is great, but not when we are trying uses of uninitialized memory. When the kernel is built with KMSAN, having kernel memory initialization enabled may introduce false negatives. We disable CONFIG_INIT_STACK_ALL_PATTERN and CONFIG_INIT_STACK_ALL_ZERO under CONFIG_KMSAN, making it impossible to auto-initialize stack variables in KMSAN builds. We also disable CONFIG_INIT_ON_ALLOC_DEFAULT_ON and CONFIG_INIT_ON_FREE_DEFAULT_ON to prevent accidental use of heap auto-initialization. We however still let the users enable heap auto-initialization at boot-time (by setting init_on_alloc=1 or init_on_free=1), in which case a warning is printed. Link: https://lkml.kernel.org/r/20220915150417.722975-31-glider@google.com Signed-off-by: Alexander Potapenko Cc: Alexander Viro Cc: Alexei Starovoitov Cc: Andrey Konovalov Cc: Andrey Konovalov Cc: Andy Lutomirski Cc: Arnd Bergmann Cc: Borislav Petkov Cc: Christoph Hellwig Cc: Christoph Lameter Cc: David Rientjes Cc: Dmitry Vyukov Cc: Eric Biggers Cc: Eric Biggers Cc: Eric Dumazet Cc: Greg Kroah-Hartman Cc: Herbert Xu Cc: Ilya Leoshkevich Cc: Ingo Molnar Cc: Jens Axboe Cc: Joonsoo Kim Cc: Kees Cook Cc: Marco Elver Cc: Mark Rutland Cc: Matthew Wilcox Cc: Michael S. Tsirkin Cc: Pekka Enberg Cc: Peter Zijlstra Cc: Petr Mladek Cc: Stephen Rothwell Cc: Steven Rostedt Cc: Thomas Gleixner Cc: Vasily Gorbik Cc: Vegard Nossum Cc: Vlastimil Babka Signed-off-by: Andrew Morton

hardening: Remove Clang's enable flag for -ftrivial-auto-var-init=zero

2022-09-30T06:05:00Z

Now that Clang's -enable-trivial-auto-var-init-zero-knowing-it-will-be-removed-from-clang option is no longer required, remove it from the command line. Clang 16 and later will warn when it is used, which will cause Kconfig to think it can't use -ftrivial-auto-var-init=zero at all. Check for whether it is required and only use it when so. Cc: Nathan Chancellor Cc: Masahiro Yamada Cc: Nick Desaulniers Cc: linux-kbuild@vger.kernel.org Cc: llvm@lists.linux.dev Cc: stable@vger.kernel.org Fixes: f02003c860d9 ("hardening: Avoid harmless Clang option under CONFIG_INIT_STACK_ALL_ZERO") Signed-off-by: Kees Cook