wireguard-linux/mm/kasan, branch stable

kasan: unpoison task stack below watermark only in generic mode

2026-09-26T20:55:10Z

CPU resume and BPF exception handling can discard stack frames without running their compiler-generated epilogues. Generic KASAN needs kasan_unpoison_task_stack_below() to clear the redzones left behind by those frames before the stack is reused. CONFIG_KASAN_STACK also enables this helper for SW_TAGS. The helper derives the stack base from an untagged stack pointer, so kasan_unpoison() writes KASAN_TAG_KERNEL (0xff) into the shadow for [base, watermark). For a vmapped task stack, vm_area->addr still carries the original random allocation tag. This creates a tag mismatch at the stack base even if that memory has never held an instrumented stack object. When the task exits and its stack is not cached, thread_stack_free_rcu() passes vm_area->addr to vfree(). In RCU callback context this reaches vfree_atomic(), whose llist_add() writes to the allocation base through the tagged pointer and triggers a false KASAN invalid-access report: BUG: KASAN: invalid-access in vfree_atomic+0x90/0x150 Write of size 8 at addr c2ffffc0a8f70000 by task rcuop/7/75 Pointer tag: [c2], memory tag: [ff] Call trace: __hwasan_store8_noabort+0xe8/0xf8 vfree_atomic+0x90/0x150 vfree+0x220/0x298 thread_stack_free_rcu+0x3c/0x4c rcu_do_batch+0x308/0xaf0 rcu_nocb_cb_kthread+0x33c/0x708 The deferred-free path started using the tagged vm_area->addr in commit 449e0b4ed5a1 ("fork: clean-up naming of vm_stack/vm_struct variables in vmap stacks code"). Previously it freed the untagged pointer derived from tsk->stack, so the write was never tag-checked. SW_TAGS does not need the blanket shadow reset to make subsequent stack accesses valid: untagged kernel pointers have the match-all 0xff tag, and the compiler initializes the shadow tags of instrumented stack objects before use. Return early unless CONFIG_KASAN_GENERIC is enabled. Keep the mode check in the common helper so it covers both resume and bpf_throw(). Link: https://lore.kernel.org/20260916175113.1327454-1-ryabinin.a.a@gmail.com Fixes: 449e0b4ed5a1 ("fork: clean-up naming of vm_stack/vm_struct variables in vmap stacks code") Signed-off-by: Andrey Ryabinin Signed-off-by: Andrew Morton Reported-by: Shaobo Huang Closes: https://lore.kernel.org/all/20260806123020.90869-1-huangshaobo3@xiaomi.com/ Assisted-by: LLM Cc: Alexander Potapenko Cc: Andrey Konovalov Cc: David Hildenbrand Cc: Dmitry Vyukov Cc: Lorenzo Stoakes Cc: Vincenzo Frascino Cc:

kasan: fix quarantine_size accounting during cache removal

2026-08-25T01:43:21Z

quarantine_size tracks the total number of bytes stored in global_quarantine[]. It is incremented when per-CPU quarantine objects are moved into the global quarantine and decremented when a global batch is evicted by kasan_quarantine_reduce(). kasan_quarantine_remove_cache() also removes objects from the global quarantine. qlist_move_cache() rebuilds the source batch and updates its .bytes field, but quarantine_size is not adjusted accordingly. As a result, quarantine_size remains over-counted by the size of the removed objects. The stale accounting accumulates across cache removals. Once the inflated value exceeds quarantine_max_size, kasan_quarantine_reduce() can evict a batch even though the actual number of bytes in global_quarantine[] is still below quarantine_max_size, shortening the quarantine window. Fix the accounting by recording each batch's size before qlist_move_cache() and subtracting the number of bytes actually removed from quarantine_size while holding quarantine_lock. A KUnit reproducer used during testing observed the over-count grow by 4698864 bytes after one kasan_quarantine_remove_cache() call with the fix reverted. With this change applied, the over-count did not grow. Link: https://lore.kernel.org/20260811073332.1351893-1-sh_def@163.com Fixes: 64abdcb24351 ("kasan: eliminate long stalls during quarantine reduction") Signed-off-by: Hui Su Reported-by: Sashiko Closes: https://sashiko.dev/#/patchset/20260808031459.3032812-1-sh_def%40163.com Reviewed-by: Andrey Ryabinin Cc: Alexander Potapenko Cc: Andrey Konovalov Cc: Dmitry Vyukov Cc: Vincenzo Frascino Signed-off-by: Andrew Morton

kasan: fix cache shrink race with CPU hotplug

2026-08-25T01:43:16Z

kasan_quarantine_remove_cache() first invokes per_cpu_remove_cache() on all online CPUs. Each callback moves objects belonging to the cache from cpu_quarantine to the CPU's shrink_qlist, where they can later be freed from task context. kmem_cache_destroy() invokes the quarantine removal path while holding cpus_read_lock(), but kmem_cache_shrink() does not. The latter can therefore race with CPU offlining as follows: kmem_cache_shrink() CPU hotplug ------------------- ----------- on_each_cpu() CPU1 moves objects to CPU1's shrink_qlist on_each_cpu() returns CPU1 goes offline kasan_cpu_offline() drains cpu_quarantine leaves shrink_qlist untouched for_each_online_cpu() skips CPU1 The objects left on CPU1's shrink_qlist are not returned to the slab allocator. This may prevent kmem_cache_shrink() from releasing slabs that would otherwise become empty. If CPU1 remains offline, a later kmem_cache_destroy() also skips the list and can report that the cache still contains objects. An intermittent occurrence was observed with a virtio-9p filesystem. The mount and umount commands both returned 0, but the kernel logged the following during the userspace-triggered teardown: [ 2994.380134][ T111] BUG 9p-fcall-cache-1 (Tainted: G B ): Objects remaining on __kmem_cache_shutdown() [ 2994.381140][ T111] Object 0xff11000004361118 @offset=4376 [ 2994.381607][ T111] Allocated in p9_fcall_init+0x201/0x400 age=19564 cpu=1 pid=104 [ 2994.382591][ T111] p9_fcall_init+0x201/0x400 [ 2994.382810][ T111] p9_tag_alloc+0x12f/0x700 [ 2994.382982][ T111] p9_client_prepare_req+0x102/0x3e0 [ 2994.383165][ T111] p9_client_rpc+0x1ab/0xa50 [ 2994.383334][ T111] p9_client_getattr_dotl+0xb0/0x1a0 [ 2994.383515][ T111] v9fs_vfs_getattr_dotl+0x115/0x360 [ 2994.383719][ T111] vfs_getattr_nosec+0x22c/0x3a0 [ 2994.383910][ T111] vfs_statx+0xd7/0x170 [ 2994.384062][ T111] vfs_fstatat+0x45/0x80 [ 2994.384215][ T111] __do_sys_newfstatat+0x84/0xe0 [ 2994.384386][ T111] do_syscall_64+0x115/0x6a0 [ 2994.384566][ T111] entry_SYSCALL_64_after_hwframe+0x77/0x7f [ 2994.399720][ T111] WARNING: mm/slub.c:1244 at __kmem_cache_shutdown+0x363/0x500, CPU#0: busybox/111 [ 2994.405655][ T111] Call Trace: [ 2994.406325][ T111] kmem_cache_destroy+0x73/0x1b0 [ 2994.406630][ T111] p9_client_destroy+0x271/0x3c0 [ 2994.407210][ T111] v9fs_session_close+0x3c/0x260 [ 2994.407409][ T111] v9fs_kill_super+0x48/0x90 [ 2994.407584][ T111] deactivate_locked_super+0xa3/0x160 [ 2994.407778][ T111] cleanup_mnt+0x1dd/0x3e0 Thus, a successful umount left objects in the 9p fcall cache and prevented the cache from being destroyed cleanly. Per-CPU shrink_qlist storage exists for every possible CPU, and each list is protected by its own raw spinlock. Iterate over possible CPUs so that a list populated before its CPU went offline is drained as well. for_each_possible_cpu() can do more work than for_each_online_cpu(), but this change only affects CONFIG_KASAN_GENERIC kernels. The extra work is limited to cache shrink and cache destruction paths and does not affect the normal allocation/free fast path. It adds one raw-spinlock-protected scan of each possible CPU's shrink list. These lists are normally empty; a non-empty list is traversed to remove objects belonging to the cache being shrunk or destroyed. Link: https://lore.kernel.org/20260808031459.3032812-1-sh_def@163.com Fixes: 07d067e4f2ce ("kasan: fix sleeping function called from invalid context on RT kernel") Signed-off-by: Hui Su Reviewed-by: Andrey Ryabinin Cc: Alexander Potapenko Cc: Andrey Konovalov Cc: Dmitry Vyukov Cc: Vincenzo Frascino Cc: "Zhang, Qiang1" Cc: Signed-off-by: Andrew Morton

mm/kasan: remove redundant initialization for kasan_flag_write_only

2026-07-29T04:11:44Z

Patch series "mm: remove redundant static variable initializations". This series removes explicit initializations of static bool variables to false within the mm/ subsystem. In C, static variables without explicit initialization are implicitly placed in the .bss section and initialized to zero/false by default. Removing these explicit initializations follows the Linux kernel coding style and avoids cluttering the data section. This patch (of 2): The static variable 'kasan_flag_write_only' is implicitly initialized to false. Remove the explicit initialization to follow the Linux kernel coding style. Link: https://lore.kernel.org/20260623114743.4565-1-igorpetindev@gmail.com Link: https://lore.kernel.org/20260623114743.4565-2-igorpetindev@gmail.com Signed-off-by: Igor Putko Reviewed-by: SeongJae Park Reviewed-by: Lance Yang Cc: Alexander Potapenko Cc: Andrey Konovalov Cc: Andrey Ryabinin Cc: Dmitry Vyukov Cc: Miaohe Lin Cc: Naoya Horiguchi Cc: Vincenzo Frascino Signed-off-by: Andrew Morton

Merge tag 'mm-stable-2026-06-18-09-26' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

2026-06-19T17:14:34Z

Pull MM updates from Andrew Morton: - "selftests/mm: clean up build output and verbosity" (Li Wang) Remove some noise from the MM selftests build - "mm: Free contiguous order-0 pages efficiently" (Ryan Roberts) Speed up the freeing of a batch of 0-order pages by first scanning them for coalescing opportunities. This is applicable to vfree() and to the releasing of frozen pages - "mm/damon: introduce DAMOS failed region quota charge ratio" (SeongJae Park) Address a DAMOS usability issue: The DAMOS quota often exhausts prematurely because it charges for all memory attempted, causing slow and inconsistent performance when actions fail on unreclaimable memory. To fix this, a new feature lets users set a smaller, flexible quota charge ratio (via a numerator and denominator) for failed regions. Since failed actions cause less overhead, reducing their quota cost ensures more predictable and efficient DAMOS processing - "selftests/cgroup: improve zswap tests robustness and support large page sizes" (Li Wang) Fix various spurious failures and improves the overall robustness of the cgroup zswap selftests - "fix MAP_DROPPABLE not supported errno" (Anthony Yznaga) Fix an issue in the mlock selftests on arm32 - "mm: huge_memory: clean up defrag sysfs with shared" (Breno Leitao) Some maintenance work in the huge_memory code - "treewide: fixup gfp_t printks" (Brendan Jackman) Use the special vprintf() gfp_t conversion in various places - "mm: Fix vmemmap optimization accounting and initialization" (Muchun Song) Fix several bugs in the vmemmap optimization, mainly around incorrect page accounting and memmap initialization in the DAX and memory hotplug paths. It also fixes pageblock migratetype initialization and struct page initialization for ZONE_DEVICE compound pages - "mm/damon: repost non-hotfix reviewed patches in damon/next tree" A sprinkle of unrelated minor bugfixes for DAMON - "mm: remove page_mapped()" (David Hildenbrand) Remove this function from the tree, replacing it with folio_mapped() - "mm/damon: let DAMON be paused and resumed" (SeongJae Park) Allow DAMON to be paused and resumed without losing its current state - "kasan: hw_tags: Disable tagging for stack and page-tables" (Muhammad Usama Anjum) Simplify and speed up kasan by removing its ineffective tagging of stacks and page tables - "mm/damon/reclaim,lru_sort: monitor all system rams by default" (SeongJae Park) Simplify deployment on diverse hardware like NUMA systems by updating DAMON_RECLAIM and DAMON_LRU_SORT to automatically monitor the physical address range covering all System RAM areas by default, replacing the overly restrictive behavior that only targeted the single largest memory block to save on negligible overhead - "mm/damon/sysfs: document filters/ directory as deprecated" (SeongJae Park) Update some DAMON docs - "mm: use spinlock guards for zone lock" (Dmitry Ilvokhin) Switch zone->lock handling over to using the guard() mechanisms - "mm/filemap: tighten mmap_miss hit accounting" (fujunjie) Fix a flaw where the mmap_miss counter over-credited page cache hits during fault-arounds and page-fault retries. This results in significant reduction of redundant synchronous mmap readahead I/O, drastically cutting down execution time and gigabytes read for sparse random or strided memory access workloads - "selftests/cgroup: Fix false positive failures in test_percpu_basic" (Li Wang) Fix a couple of false-positives in the cgroup kmem selftests - "mm/damon/reclaim: support monitoring intervals auto-tuning" (SeongJae Park) Add a new parameter to DAMON permitting DAMON_RECLAIM to automatically tune DAMON's sampling and aggregation intervals - "mm/damon/stat: add kdamond_pid parameter" (SeongJae Park) Change DAMON_STAT to provide the pid of its kdamond - "mm/kmemleak: dedupe verbose scan output" (Breno Leitao) Remove large amounts of duplicated backtraces from the verbose-mode kmemleak output - "mm: remove CONFIG_HAVE_BOOTMEM_INFO_NODE (Part 1)" (David Hildenbrand) Reduce our use of CONFIG_HAVE_BOOTMEM_INFO_NODE, with a view to removing it entirely in a later series - "mm/damon: validate min_region_size to be power of 2" (Liew Rui Yan) Prevent users from passing a non-power-of-2 value of `addr_unit', as this later results in undesirable behavior - "mm: document read_pages and simplify usage" (Frederick Mayle) - "tools/mm/page-types: Fix misc bugs" (Ye Liu) Fix three issues in tools/mm/page-types.c - "mm: misc cleanups from __GFP_UNMAPPED series" (Brendan Jackman) Implement several cleanups in the page allocator and related code - "mm, swap: swap table phase IV: unify allocation" (Kairui Song) Unify the allocation and charging of anon and shmem swap in folios, provides better synchronization, consolidates the metadata management, hence dropping the static array and map, and improves performance - "mm/damon: introduce data attributes monitoring" (SeongJae Park( Extend DAMON to monitor general data attributes other than accesses - "mm/vmalloc: free unused pages on vrealloc() shrink" (Shivam Kalra) Implement the TODO in vrealloc() to unmap and free unused pages when shrinking across a page boundary - "mm/damon: documentation and comment fixes" (niecheng) - "remove mmap_action success, error hooks" (Lorenzo Stoakes) Eliminate custom hooks from mmap_action by removing the problematic success_hook which allowed drivers to improperly access uninitialized VMAs. It replaces the error_hook with a simple error-code field and updates the memory char driver accordingly - "mm/damon: minor improvements for code readability and tests" (SeongJae Park) - "mm/damon: fix macro arguments and clarify quota goals doc" (Maksym Shcherba) - "userfaultfd: merge fs/userfaultfd.c into mm/userfaultfd.c" (Mike Rapoport) - "mm/mglru: improve reclaim loop and dirty folio" (Kairui Song and others) Clean up and slightly improves MGLRU's reclaim loop and dirty writeback handling. Large performance improvements are measured - "use vma locks for proc/pid/{smaps|numa_maps} reads" (Suren Baghdasaryan) Use per-vma locks when reading /proc/pid/smaps and numa_maps similar to reduce contention on central mmap_lock - "refactors thpsize_shmem_enabled_store() and thpsize_shmem_enabled_show()" (Ran Xiaokai) Some cleanup work in the THP code - "selftests/memfd: fix compilation warnings" (Konstantin Khorenko) Fix a few build glitches in the memfd selftest code. - "memcg: shrink obj_stock_pcp and cache multiple objcgs" (Shakeel Butt) Resolve a 68% performance regression caused by NUMA-node cache thrashing around struct obj_stock_pcp by shrinking its existing fields and expanding it into a multi-slot array that caches up to five obj_cgroup pointers per CPU, allowing per-node variants of the same memcg to coexist within a single 64-byte cache line. - "zram: writeback fixes" (Sergey Senozhatsky) address a couple of unrelated zram writeback issues - "mm: switch THP shrinker to list_lru" (Johannes Weiner) Resolve NUMA-awareness issues and streamlines callsite interaction by refactoring and extending the list_lru API to completely replace the complex, open-coded deferred split queue for Transparent Huge Pages - "mm: improve large folio readahead for exec memory" (Usama Arif) Improve large-folio readahead on systems like 64K-page arm64 by preventing the mmap_miss check from permanently disabling target-oriented VM_EXEC readahead, and by generalizing the force_thp_readahead gate to support mappings with any usefully large maximum folio order under the cache cap. - "userfaultfd/pagemap: pre-existing fixes" (Kiryl Shutsemau) Fix a bunch of minor issues in the userfaultfd/pagemap, all of which were flagged by Sashiko review of proposed new material - "mm/sparse-vmemmap: Provide generic vmemmap_set_pmd() and vmemmap_check_pmd()" (Muchun Song) Provide generic versions of these two functions so the four arch-specific implementations can be removed. - "mm/swap, PM: hibernate: fix swapoff race in uswsusp by pinning swap device" (Youngjun Park) Address a uswsusp-vs-swapoff race and reduces the swap device reference taking/releasing frequency. - "mm/hmm: A fix and a selftest" (Dev Jain) * tag 'mm-stable-2026-06-18-09-26' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (321 commits) selftests/mm/hmm-tests: test pagemap reads of PMD device-private entries fs/proc/task_mmu: do not warn on seeing non-migration pmd entry lib/test_hmm: check alloc_page_vma() return value and handle OOM mm/compaction: cap compact_gap() at COMPACT_CLUSTER_MAX mm/swap: remove redundant swap device reference in alloc/free mm/swap, PM: hibernate: fix swapoff race in uswsusp by pinning swap device mm/filemap: use folio_next_index() for start vmalloc: fix NULL pointer dereference in is_vm_area_hugepages() sparc/mm: drop vmemmap_check_pmd helper and use generic code loongarch/mm: drop vmemmap_check_pmd helper and use generic code riscv/mm: drop vmemmap_pmd helpers and use generic code arm64/mm: drop vmemmap_pmd helpers and use generic code mm/sparse-vmemmap: provide generic vmemmap_set_pmd() and vmemmap_check_pmd() rust: page: mark Page::nid as inline userfaultfd: build __VMA_UFFD_FLAGS from config-gated masks userfaultfd: gate must_wait writability check on pte_present() mm/huge_memory: preserve pmd_swp_uffd_wp on device-private PMD downgrade fs/proc/task_mmu: fix hugetlb self-deadlock in pagemap_scan_pte_hole() fs/proc/task_mmu: use huge_page_size() in pagemap_scan_hugetlb_entry() fs/proc/task_mmu: fix make_uffd_wp_huge_pte() prot-update race ...

Merge tag 'slab-for-7.2' of git://git.kernel.org/pub/scm/linux/kernel/git/vbabka/slab

2026-06-16T03:14:43Z

Pull slab updates from Vlastimil Babka: - Support for "allocation tokens" (currently available in Clang 22+) for smarter partitioning of kmalloc caches based on the allocated object type, which can be enabled instead of the "random" per-caller-address-hash partitioning. It should be able to deterministically separate types containing a pointer from those that do not (Marco Elver) - Improvements and simplification of the kmem_cache_alloc_bulk() and mempool_alloc_bulk() API. This includes adaptation of callers (Christoph Hellwig) - Performance improvements and cleanups related mostly to sheaves refill (Hao Li, Shengming Hu, Vlastimil Babka) - Several fixups for the slabinfo tool (Xuewen Wang) * tag 'slab-for-7.2' of git://git.kernel.org/pub/scm/linux/kernel/git/vbabka/slab: mm/slab: do not limit zeroing to orig_size when only red zoning is enabled mm/slub: preserve original size in _kmalloc_nolock_noprof retry path mm: simplify the mempool_alloc_bulk API mm/slab: improve kmem_cache_alloc_bulk mm/slub: detach and reattach partial slabs in batch mm/slub: introduce helpers for node partial slab state mm/slub: use empty sheaf helpers for oversized sheaves tools/mm/slabinfo: remove redundant slab->partial assignment tools/mm/slabinfo: remove dead assignment in get_obj_and_str() tools/mm/slabinfo: Fix trace disable logic inversion MAINTAINERS: add slab-related scripts and tools to SLAB ALLOCATOR mm/slub: fix typo in sheaves comment mm, slab: simplify returning slab in __refill_objects_node() mm, slab: add an optimistic __slab_try_return_freelist() slab: fix kernel-docs for mm-api slab: improve KMALLOC_PARTITION_RANDOM randomness slab: support for compiler-assisted type-based slab cache partitioning mm/slub: defer freelist construction until after bulk allocation from a new slab

kasan: Move generic KASAN page tables out of BSS too

2026-06-05T10:44:10Z

Make sure that all KASAN page tables are emitted into the .pgtbl section (provided that the arch has one - otherwise, fall back to page aligned BSS) This is needed because BSS itself is no longer accessible via the linear map on arm64. Cc: Andrey Ryabinin Cc: Alexander Potapenko Cc: Andrey Konovalov Cc: Dmitry Vyukov Cc: Vincenzo Frascino Cc: kasan-dev@googlegroups.com Signed-off-by: Ard Biesheuvel Signed-off-by: Will Deacon

kasan/test: only do kmalloc_double_kzfree for generic mode

2026-06-04T21:45:02Z

kmalloc_double_kzfree() would corrupt kernel memory when the just freed memory were allocated by another thread before the second call to kfree_sensitive() and the new allocation tag happened to match the old one. This could not happen in GENERIC mode as it uses quarantine. Link: https://lore.kernel.org/20260524031053.381776-1-wsw9603@163.com Signed-off-by: Wang Wensheng Reviewed-by: Andrey Konovalov Cc: Alexander Potapenko Cc: Andrey Ryabinin Cc: Dmitry Vyukov Cc: Vincenzo Frascino Signed-off-by: Andrew Morton

mm/slab: improve kmem_cache_alloc_bulk

2026-06-03T16:20:43Z

The kmem_cache_alloc_bulk return value is weird. It returns the number of allocated objects, but that must always be 0 or the requested number based on the implementations and the handling in the callers, but that assumption is not actually documented anywhere, which confuses automated review tools. Fix this by returning a bool if the allocation succeeded and adding a kerneldoc comment explaining the API. [rob.clark@oss.qualcomm.com: fixups in msm_iommu_pagetable_prealloc_allocate() ] Signed-off-by: Christoph Hellwig Reviewed-by: Alexander Lobakin # skbuff Link: https://patch.msgid.link/20260528093437.2519248-2-hch@lst.de Signed-off-by: Vlastimil Babka (SUSE)

kasan: fix bug type classification for SW_TAGS mode

2026-04-05T20:53:18Z

kasan_non_canonical_hook() derives orig_addr from kasan_shadow_to_mem(), but the pointer tag may remain in the top byte. In SW_TAGS mode this tagged address is compared against PAGE_SIZE and TASK_SIZE, which leads to incorrect bug classification. As a result, NULL pointer dereferences may be reported as "wild-memory-access". Strip the tag before performing these range checks and use the untagged value when reporting addresses in these ranges. Before: [ ] Unable to handle kernel paging request at virtual address ffef800000000000 [ ] KASAN: maybe wild-memory-access in range [0xff00000000000000-0xff0000000000000f] After: [ ] Unable to handle kernel paging request at virtual address ffef800000000000 [ ] KASAN: null-ptr-deref in range [0x0000000000000000-0x000000000000000f] Link: https://lkml.kernel.org/r/20260305185659.20807-1-ryabinin.a.a@gmail.com Signed-off-by: Andrey Ryabinin Cc: Alexander Potapenko Cc: Andrey Konovalov Cc: Dmitry Vyukov Cc: Maciej Wieczor-Retman Cc: Vincenzo Frascino Signed-off-by: Andrew Morton