kernel/linux.git/mm/kfence, branch v6.19.12

mm/kfence: disable KFENCE upon KASAN HW tags enablement

2026-03-19T15:15:09+00:00

commit 09833d99db36d74456a4d13eb29c32d56ff8f2b6 upstream. KFENCE does not currently support KASAN hardware tags. As a result, the two features are incompatible when enabled simultaneously. Given that MTE provides deterministic protection and KFENCE is a sampling-based debugging tool, prioritize the stronger hardware protections. Disable KFENCE initialization and free the pre-allocated pool if KASAN hardware tags are detected to ensure the system maintains the security guarantees provided by MTE. Link: https://lkml.kernel.org/r/20260213095410.1862978-1-glider@google.com Fixes: 0ce20dd84089 ("mm: add Kernel Electric-Fence infrastructure") Signed-off-by: Alexander Potapenko Suggested-by: Marco Elver Reviewed-by: Marco Elver Cc: Andrey Konovalov Cc: Andrey Ryabinin Cc: Dmitry Vyukov Cc: Ernesto Martinez Garcia Cc: Greg KH Cc: Kees Cook Cc: Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman

mm/kfence: fix KASAN hardware tag faults during late enablement

2026-03-19T15:15:09+00:00

commit d155aab90fffa00f93cea1f107aef0a3d548b2ff upstream. When KASAN hardware tags are enabled, re-enabling KFENCE late (via /sys/module/kfence/parameters/sample_interval) causes KASAN faults. This happens because the KFENCE pool and metadata are allocated via the page allocator, which tags the memory, while KFENCE continues to access it using untagged pointers during initialization. Use __GFP_SKIP_KASAN for late KFENCE pool and metadata allocations to ensure the memory remains untagged, consistent with early allocations from memblock. To support this, add __GFP_SKIP_KASAN to the allowlist in __alloc_contig_verify_gfp_mask(). Link: https://lkml.kernel.org/r/20260220144940.2779209-1-glider@google.com Fixes: 0ce20dd84089 ("mm: add Kernel Electric-Fence infrastructure") Signed-off-by: Alexander Potapenko Suggested-by: Ernesto Martinez Garcia Cc: Andrey Konovalov Cc: Andrey Ryabinin Cc: Dmitry Vyukov Cc: Greg KH Cc: Kees Cook Cc: Marco Elver Cc: Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman

mm/kfence: randomize the freelist on initialization

2026-01-27T03:03:48+00:00

Randomize the KFENCE freelist during pool initialization to make allocation patterns less predictable. This is achieved by shuffling the order in which metadata objects are added to the freelist using get_random_u32_below(). Additionally, ensure the error path correctly calculates the address range to be reset if initialization fails, as the address increment logic has been moved to a separate loop. Link: https://lkml.kernel.org/r/20260120161510.3289089-1-pimyn@google.com Fixes: 0ce20dd84089 ("mm: add Kernel Electric-Fence infrastructure") Signed-off-by: Pimyn Girgis Reviewed-by: Alexander Potapenko Cc: Dmitry Vyukov Cc: Marco Elver Cc: Ernesto Martnez Garca Cc: Greg KH Cc: Kees Cook Cc: Signed-off-by: Andrew Morton

mm/kfence: fix potential deadlock in reboot notifier

2026-01-20T17:34:26+00:00

The reboot notifier callback can deadlock when calling cancel_delayed_work_sync() if toggle_allocation_gate() is blocked in wait_event_idle() waiting for allocations, that might not happen on shutdown path. The issue is that cancel_delayed_work_sync() waits for the work to complete, but the work is waiting for kfence_allocation_gate > 0 which requires allocations to happen (each allocation is increased by 1) - allocations that may have stopped during shutdown. Fix this by: 1. Using cancel_delayed_work() (non-sync) to avoid blocking. Now the callback succeeds and return. 2. Adding wake_up() to unblock any waiting toggle_allocation_gate() 3. Adding !kfence_enabled to the wait condition so the wake succeeds The static_branch_disable() IPI will still execute after the wake, but at this early point in shutdown (reboot notifier runs with INT_MAX priority), the system is still functional and CPUs can respond to IPIs. Link: https://lkml.kernel.org/r/20260116-kfence_fix-v1-1-4165a055933f@debian.org Fixes: ce2bba89566b ("mm/kfence: add reboot notifier to disable KFENCE on shutdown") Signed-off-by: Breno Leitao Reported-by: Chris Mason Closes: https://lore.kernel.org/all/20260113140234.677117-1-clm@meta.com/ Reviewed-by: Marco Elver Cc: Alexander Potapenko Cc: Breno Leitao Cc: Chris Mason Cc: Dmitriy Vyukov Signed-off-by: Andrew Morton

Merge tag 'mm-stable-2025-12-03-21-26' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

2025-12-05T21:52:43+00:00

Pull MM updates from Andrew Morton: "__vmalloc()/kvmalloc() and no-block support" (Uladzislau Rezki) Rework the vmalloc() code to support non-blocking allocations (GFP_ATOIC, GFP_NOWAIT) "ksm: fix exec/fork inheritance" (xu xin) Fix a rare case where the KSM MMF_VM_MERGE_ANY prctl state is not inherited across fork/exec "mm/zswap: misc cleanup of code and documentations" (SeongJae Park) Some light maintenance work on the zswap code "mm/page_owner: add debugfs files 'show_handles' and 'show_stacks_handles'" (Mauricio Faria de Oliveira) Enhance the /sys/kernel/debug/page_owner debug feature by adding unique identifiers to differentiate the various stack traces so that userspace monitoring tools can better match stack traces over time "mm/page_alloc: pcp->batch cleanups" (Joshua Hahn) Minor alterations to the page allocator's per-cpu-pages feature "Improve UFFDIO_MOVE scalability by removing anon_vma lock" (Lokesh Gidra) Address a scalability issue in userfaultfd's UFFDIO_MOVE operation "kasan: cleanups for kasan_enabled() checks" (Sabyrzhan Tasbolatov) "drivers/base/node: fold node register and unregister functions" (Donet Tom) Clean up the NUMA node handling code a little "mm: some optimizations for prot numa" (Kefeng Wang) Cleanups and small optimizations to the NUMA allocation hinting code "mm/page_alloc: Batch callers of free_pcppages_bulk" (Joshua Hahn) Address long lock hold times at boot on large machines. These were causing (harmless) softlockup warnings "optimize the logic for handling dirty file folios during reclaim" (Baolin Wang) Remove some now-unnecessary work from page reclaim "mm/damon: allow DAMOS auto-tuned for per-memcg per-node memory usage" (SeongJae Park) Enhance the DAMOS auto-tuning feature "mm/damon: fixes for address alignment issues in DAMON_LRU_SORT and DAMON_RECLAIM" (Quanmin Yan) Fix DAMON_LRU_SORT and DAMON_RECLAIM with certain userspace configuration "expand mmap_prepare functionality, port more users" (Lorenzo Stoakes) Enhance the new(ish) file_operations.mmap_prepare() method and port additional callsites from the old ->mmap() over to ->mmap_prepare() "Fix stale IOTLB entries for kernel address space" (Lu Baolu) Fix a bug (and possible security issue on non-x86) in the IOMMU code. In some situations the IOMMU could be left hanging onto a stale kernel pagetable entry "mm/huge_memory: cleanup __split_unmapped_folio()" (Wei Yang) Clean up and optimize the folio splitting code "mm, swap: misc cleanup and bugfix" (Kairui Song) Some cleanups and a minor fix in the swap discard code "mm/damon: misc documentation fixups" (SeongJae Park) "mm/damon: support pin-point targets removal" (SeongJae Park) Permit userspace to remove a specific monitoring target in the middle of the current targets list "mm: MISC follow-up patches for linux/pgalloc.h" (Harry Yoo) A couple of cleanups related to mm header file inclusion "mm/swapfile.c: select swap devices of default priority round robin" (Baoquan He) improve the selection of swap devices for NUMA machines "mm: Convert memory block states (MEM_*) macros to enums" (Israel Batista) Change the memory block labels from macros to enums so they will appear in kernel debug info "ksm: perform a range-walk to jump over holes in break_ksm" (Pedro Demarchi Gomes) Address an inefficiency when KSM unmerges an address range "mm/damon/tests: fix memory bugs in kunit tests" (SeongJae Park) Fix leaks and unhandled malloc() failures in DAMON userspace unit tests "some cleanups for pageout()" (Baolin Wang) Clean up a couple of minor things in the page scanner's writeback-for-eviction code "mm/hugetlb: refactor sysfs/sysctl interfaces" (Hui Zhu) Move hugetlb's sysfs/sysctl handling code into a new file "introduce VM_MAYBE_GUARD and make it sticky" (Lorenzo Stoakes) Make the VMA guard regions available in /proc/pid/smaps and improves the mergeability of guarded VMAs "mm: perform guard region install/remove under VMA lock" (Lorenzo Stoakes) Reduce mmap lock contention for callers performing VMA guard region operations "vma_start_write_killable" (Matthew Wilcox) Start work on permitting applications to be killed when they are waiting on a read_lock on the VMA lock "mm/damon/tests: add more tests for online parameters commit" (SeongJae Park) Add additional userspace testing of DAMON's "commit" feature "mm/damon: misc cleanups" (SeongJae Park) "make VM_SOFTDIRTY a sticky VMA flag" (Lorenzo Stoakes) Address the possible loss of a VMA's VM_SOFTDIRTY flag when that VMA is merged with another "mm: support device-private THP" (Balbir Singh) Introduce support for Transparent Huge Page (THP) migration in zone device-private memory "Optimize folio split in memory failure" (Zi Yan) "mm/huge_memory: Define split_type and consolidate split support checks" (Wei Yang) Some more cleanups in the folio splitting code "mm: remove is_swap_[pte, pmd]() + non-swap entries, introduce leaf entries" (Lorenzo Stoakes) Clean up our handling of pagetable leaf entries by introducing the concept of 'software leaf entries', of type softleaf_t "reparent the THP split queue" (Muchun Song) Reparent the THP split queue to its parent memcg. This is in preparation for addressing the long-standing "dying memcg" problem, wherein dead memcg's linger for too long, consuming memory resources "unify PMD scan results and remove redundant cleanup" (Wei Yang) A little cleanup in the hugepage collapse code "zram: introduce writeback bio batching" (Sergey Senozhatsky) Improve zram writeback efficiency by introducing batched bio writeback support "memcg: cleanup the memcg stats interfaces" (Shakeel Butt) Clean up our handling of the interrupt safety of some memcg stats "make vmalloc gfp flags usage more apparent" (Vishal Moola) Clean up vmalloc's handling of incoming GFP flags "mm: Add soft-dirty and uffd-wp support for RISC-V" (Chunyan Zhang) Teach soft dirty and userfaultfd write protect tracking to use RISC-V's Svrsw60t59b extension "mm: swap: small fixes and comment cleanups" (Youngjun Park) Fix a small bug and clean up some of the swap code "initial work on making VMA flags a bitmap" (Lorenzo Stoakes) Start work on converting the vma struct's flags to a bitmap, so we stop running out of them, especially on 32-bit "mm/swapfile: fix and cleanup swap list iterations" (Youngjun Park) Address a possible bug in the swap discard code and clean things up a little [ This merge also reverts commit ebb9aeb980e5 ("vfio/nvgrace-gpu: register device memory for poison handling") because it looks broken to me, I've asked for clarification - Linus ] * tag 'mm-stable-2025-12-03-21-26' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (321 commits) mm: fix vma_start_write_killable() signal handling mm/swapfile: use plist_for_each_entry in __folio_throttle_swaprate mm/swapfile: fix list iteration when next node is removed during discard fs/proc/task_mmu.c: fix make_uffd_wp_huge_pte() huge pte handling mm/kfence: add reboot notifier to disable KFENCE on shutdown memcg: remove inc/dec_lruvec_kmem_state helpers selftests/mm/uffd: initialize char variable to Null mm: fix DEBUG_RODATA_TEST indentation in Kconfig mm: introduce VMA flags bitmap type tools/testing/vma: eliminate dependency on vma->__vm_flags mm: simplify and rename mm flags function for clarity mm: declare VMA flags by bit zram: fix a spelling mistake mm/page_alloc: optimize lowmem_reserve max lookup using its semantic monotonicity mm/vmscan: skip increasing kswapd_failures when reclaim was boosted pagemap: update BUDDY flag documentation mm: swap: remove scan_swap_map_slots() references from comments mm: swap: change swap_alloc_slow() to void mm, swap: remove redundant comment for read_swap_cache_async mm, swap: use SWP_SOLIDSTATE to determine if swap is rotational ...

mm/kfence: add reboot notifier to disable KFENCE on shutdown

2025-11-29T18:41:10+00:00

During system shutdown, KFENCE can cause IPI synchronization issues if it remains active through the reboot process. To prevent this, register a reboot notifier that disables KFENCE and cancels any pending timer work early in the shutdown sequence. This is only necessary when CONFIG_KFENCE_STATIC_KEYS is enabled, as this configuration sends IPIs that can interfere with shutdown. Without static keys, no IPIs are generated and KFENCE can safely remain active. The notifier uses maximum priority (INT_MAX) to ensure KFENCE shuts down before other subsystems that might still depend on stable memory allocation behavior. This fixes a late kexec CSD lockup[1] when kfence is trying to IPI a CPU that is busy in a IRQ-disabled context printing characters to the console. Link: https://lkml.kernel.org/r/20251127-kfence-v2-1-daeccb5ef9aa@debian.org Link: https://lkml.kernel.org/r/20251126-kfence-v1-1-5a6e1d7c681c@debian.org Link: https://lore.kernel.org/all/sqwajvt7utnt463tzxgwu2yctyn5m6bjwrslsnupfexeml6hkd@v6sqmpbu3vvu/ [1] Fixes: 0ce20dd84089 ("mm: add Kernel Electric-Fence infrastructure") Signed-off-by: Breno Leitao Reviewed-by: Marco Elver Cc: Alexander Potapenko Cc: Dmitriy Vyukov Signed-off-by: Andrew Morton

slab: Reimplement page_slab()

2025-11-13T10:01:08+00:00

In order to separate slabs from folios, we need to convert from any page in a slab to the slab directly without going through a page to folio conversion first. Up to this point, page_slab() has followed the example of other memdesc converters (page_folio(), page_ptdesc() etc) and just cast the pointer to the requested type, regardless of whether the pointer is actually a pointer to the correct type or not. That changes with this commit; we check that the page actually belongs to a slab and return NULL if it does not. Other memdesc converters will adopt this convention in future. kfence was the only user of page_slab(), so adjust it to the new way of working. It will need to be touched again when we separate slab from page. Signed-off-by: Matthew Wilcox (Oracle) Cc: Alexander Potapenko Cc: Marco Elver Cc: kasan-dev@googlegroups.com Link: https://patch.msgid.link/20251113000932.1589073-2-willy@infradead.org Acked-by: David Hildenbrand (Red Hat) Tested-by: Marco Elver Reviewed-by: Harry Yoo Signed-off-by: Vlastimil Babka

kfence: drop nth_page() usage

2025-09-21T21:22:09+00:00

We want to get rid of nth_page(), and kfence init code is the last user. Unfortunately, we might actually walk a PFN range where the pages are not contiguous, because we might be allocating an area from memblock that could span memory sections in problematic kernel configs (SPARSEMEM without SPARSEMEM_VMEMMAP). We could check whether the page range is contiguous using page_range_contiguous() and failing kfence init, or making kfence incompatible these problemtic kernel configs. Let's keep it simple and simply use pfn_to_page() by iterating PFNs. Link: https://lkml.kernel.org/r/20250901150359.867252-36-david@redhat.com Signed-off-by: David Hildenbrand Reviewed-by: Marco Elver Reviewed-by: Lorenzo Stoakes Cc: Alexander Potapenko Cc: Dmitry Vyukov Signed-off-by: Andrew Morton

kfence: Remove mention of PG_slab

2025-07-23T09:55:22+00:00

Improve the documentation slightly, assuming I understood it correctly. Signed-off-by: Matthew Wilcox (Oracle) Acked-by: Harry Yoo Link: https://patch.msgid.link/20250611155916.2579160-10-willy@infradead.org Signed-off-by: Vlastimil Babka

kfence: skip __GFP_THISNODE allocations on NUMA systems

2025-02-01T11:53:26+00:00

On NUMA systems, __GFP_THISNODE indicates that an allocation _must_ be on a particular node, and failure to allocate on the desired node will result in a failed allocation. Skip __GFP_THISNODE allocations if we are running on a NUMA system, since KFENCE can't guarantee which node its pool pages are allocated on. Link: https://lkml.kernel.org/r/20250124120145.410066-1-elver@google.com Fixes: 236e9f153852 ("kfence: skip all GFP_ZONEMASK allocations") Signed-off-by: Marco Elver Reported-by: Vlastimil Babka Acked-by: Vlastimil Babka Cc: Christoph Lameter Cc: Alexander Potapenko Cc: Chistoph Lameter Cc: Dmitriy Vyukov Cc: Signed-off-by: Andrew Morton