kernel/linux.git/mm, branch v6.18.35

mm/slub: hold cpus_read_lock around flush_rcu_sheaves_on_cache()

2026-06-09T10:28:52+00:00

[ Upstream commit 67ea9d353d0ba12bdbc9183ff568dead9e949b80 ] flush_rcu_sheaves_on_cache() calls queue_work_on() in a for_each_online_cpu() loop, which requires the cpu to stay online. But cpus_read_lock() is not held in kvfree_rcu_barrier_on_cache() and the set of "online cpus" is subject to change. There are two paths that call flush_rcu_sheaves_on_cache(): // has cpus_read_lock() flush_all_rcu_sheaves() -> flush_rcu_sheaves_on_cache() // no cpus_read_lock() kvfree_rcu_barrier_on_cache() -> flush_rcu_sheaves_on_cache() Fix this by holding cpus_read_lock() in kvfree_rcu_barrier_on_cache(). Why not move cpus_read_lock() from flush_all_rcu_sheaves() into flush_rcu_sheaves_on_cache()? The reason is it would introduce a new lock order (slab_mutex -> cpu_hotplug_lock). The reverse order (cpu_hotplug_lock -> slab_mutex) is established by - cpuhp_setup_state_nocalls(..., slub_cpu_setup, ...) - kmem_cache_destroy() The two orders together would form an AB-BA deadlock. Finally, add lockdep_assert_cpus_held() in flush_rcu_sheaves_on_cache() to catch the same problem in the future. Fixes: 0f35040de593 ("mm/slab: introduce kvfree_rcu_barrier_on_cache() for cache destruction") Cc: Signed-off-by: Qing Wang Link: https://patch.msgid.link/20260512035035.762317-1-wangqing7171@gmail.com Signed-off-by: Vlastimil Babka (SUSE) Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

mm/rmap: initialize nr_pages to 1 at loop start in try_to_unmap_one

2026-06-09T10:28:34+00:00

commit 3f8968e9cbf95d5d87d32218906cab0b9b9eddbe upstream. Initialize nr_pages to 1 at the start of each loop iteration, like folio_referenced_one() does. Without this, nr_pages computed by a previous folio_unmap_pte_batch() call can be reused on a later iteration that does not run folio_unmap_pte_batch() again. mmap a 64K large folio with MAP_ANONYMOUS | MAP_DROPPABLE, then call madvise(MADV_FREE), then make the last page device-exclusive via HMM_DMIRROR_EXCLUSIVE. Trigger node reclaim through sysfs. Now, in try_to_unmap_one(), we will first clear the first 15 out of 16 entries mapping the lazyfree folio. This will set nr_pages to 15. In the next pvmw walk, this nr_pages gets reused on a device-exclusive pte, thus potentially corrupting folio refcount/mapcount. At the moment, I have a userspace program which can make the kernel spit out a trace, but the blow up is in folio_referenced_one(), because there are existing bugs in the interaction between device-private and rmap (which too I am investigating). I did a one liner kernel change to avoid going into folio_referenced_one(), and the kernel blows up at folio_remove_rmap_ptes in try_to_unmap_one which is what I wanted. Note that the bug is there not since file folio batching but lazyfree folio batching, since device-exclusive only works for anonymous folios. Userspace visible effect is simply kernel crashing somewhere due to refcount/mapcount corruption. Link: https://lore.kernel.org/20260518063656.3721056-1-dev.jain@arm.com Fixes: 354dffd29575 ("mm: support batched unmap for lazyfree large folios during reclamation") Signed-off-by: Dev Jain Acked-by: Barry Song Acked-by: David Hildenbrand (Arm) Reviewed-by: Lorenzo Stoakes Cc: Anshuman Khandual Cc: Barry Song Cc: Dev Jain Cc: Harry Yoo Cc: Jann Horn Cc: Liam R. Howlett Cc: Rik van Riel Cc: Ryan Roberts Cc: Vlastimil Babka Cc: Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman

memfd: deny writeable mappings when implying SEAL_WRITE

2026-06-09T10:28:34+00:00

commit 3b041514cb6eae45869b020f743c14d983363222 upstream. When SEAL_EXEC is added, SEAL_WRITE is implied to make W^X. But the implied seal is set after the check that makes sure the memfd can not have any writable mappings. This means one can use SEAL_EXEC to apply SEAL_WRITE while having writeable mappings. This breaks the contract that SEAL_WRITE provides and can be used by an attacker to pass a memfd that appears to be write sealed but can still be modified arbitrarily. Fix this by adding the implied seals before the call for mapping_deny_writable() is done. Link: https://lore.kernel.org/20260505133922.797635-1-pratyush@kernel.org Fixes: c4f75bc8bd6b ("mm/memfd: add write seals when apply SEAL_EXEC to executable memfd") Signed-off-by: Pratyush Yadav (Google) Reviewed-by: Pasha Tatashin Acked-by: Jeff Xu Cc: Baolin Wang Cc: Brendan Jackman Cc: Greg Thelen Cc: Hugh Dickins Cc: Kees Cook Cc: "David Hildenbrand (Arm)" Cc: Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman

mm: memcontrol: propagate NMI slab stats to memcg vmstats

2026-06-09T10:28:34+00:00

commit e16f17a9c5af50221184d1ef4be4056bf3c4209e upstream. flush_nmi_stats() drains per-node NMI slab atomics into the per-node lruvec_stats, but does not propagate them to the memcg-level vmstats. For non NMI case, account_slab_nmi_safe() calls mod_memcg_lruvec_state() which updates both per-node lruvec_stats and memcg-level vmstats, so flush_nmi_stats() needs to flush to per-node lruvec_stats as well as memcg-level vmstats. So fix this by flushing to the memcg-level vmstats for NMI too. Link: https://lore.kernel.org/20260518082830.599102-1-alex@ghiti.fr Fixes: 940b01fc8dc1 ("memcg: nmi safe memcg stats for specific archs") Signed-off-by: Alexandre Ghiti Acked-by: Shakeel Butt Acked-by: Johannes Weiner Reviewed-by: Harry Yoo (Oracle) Cc: Michal Hocko Cc: Muchun Song Cc: Roman Gushchin Cc: Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman

mm/damon/sysfs-schemes: delete tried region in regions_rmdirs()

2026-06-09T10:28:34+00:00

commit 441f92f7d386b85bad16de49db95a307cba048a2 upstream. DAMON sysfs maintains the DAMOS tried region directory objects via a linked list. When the user requests refresh of the directories, DAMON sysfs removes all the region directories first, and then generate updated regions directory on the empty space. The removal function (damon_sysfs_scheme_regions_rm_dirs()) only puts the kobj objects. Deletion of the container region object from the linked list is done inside the kobj release callback function. If somehow the callback invocation is delayed, the list will contain regions list that gonna be freed. If the updated region directories creation is started in this situation, the list can be corrupted and use-after-free can happen. Because the kobj objects are managed by only DAMON sysfs, the issue cannot happen in normal situation. But, such delays can be made on kernels that built with CONFIG_DEBUG_KOBJECT_RELEASE. On the kernel, the issue can indeed be reproduced like below. # damo start --damos_action stat # cd /sys/kernel/mm/damon/admin/kdamonds/0/ # for i in {1..10}; do echo update_schemes_tried_regions > state; done # dmesg | grep underflow [ 89.296152] refcount_t: underflow; use-after-free. Fix the issue by removing the region object from the list when decrementing the reference count. Also update damos_sysfs_populate_region_dir() to add the region object to the list only after the kobject_init_and_add() is success, so that fail of kobject_init_and_add() is not leaving the deallocated object on the list. The issue was discovered [1] by Sashiko. Link: https://lore.kernel.org/20260518152559.93038-1-sj@kernel.org Link: https://lore.kernel.org/20260513011920.119183-1-sj@kernel.org [1] Fixes: 9277d0367ba1 ("mm/damon/sysfs-schemes: implement scheme region directory") Signed-off-by: SeongJae Park Cc: # 6.2.x Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman

cgroup/rstat: validate cpu before css_rstat_cpu() access

2026-06-01T15:51:03+00:00

[ Upstream commit 8817005efbdfdf5d4e4814cb5dc52b53d12917d7 ] css_rstat_updated() is exposed as a BPF kfunc and accepts a caller-provided cpu argument. The function uses cpu for per-cpu rstat lookups without checking whether it refers to a valid possible CPU. A BPF iter/cgroup program with CAP_BPF and CAP_PERFMON can pass an invalid cpu value. On an unfixed UBSCAN_BOUNDS test kernel, cpu == 0x7fffffff triggers: UBSAN: array-index-out-of-bounds in kernel/cgroup/rstat.c:31:9 index 2147483647 is out of range for type 'long unsigned int [64]' Call Trace: css_rstat_updated bpf_iter_run_prog cgroup_iter_seq_show bpf_seq_read Add cpu validation to the BPF-facing css_rstat_updated() kfunc and move the common implementation to __css_rstat_updated() for in-kernel callers. Fixes: a319185be9f5 ("cgroup: bpf: enable bpf programs to integrate with rstat") Signed-off-by: Qing Ming Signed-off-by: Tejun Heo Signed-off-by: Sasha Levin

mm/page_alloc: fix initialization of tags of the huge zero folio with init_on_free

2026-06-01T15:50:41+00:00

commit 6a288a4ddb4a994490505ab5f41c445f8e6b6467 upstream. __GFP_ZEROTAGS semantics are currently a bit weird, but effectively this flag is only ever set alongside __GFP_ZERO and __GFP_SKIP_KASAN. If we run with init_on_free, we will zero out pages during __free_pages_prepare(), to skip zeroing on the allocation path. However, when allocating with __GFP_ZEROTAG set, post_alloc_hook() will consequently not only skip clearing page content, but also skip clearing tag memory. Not clearing tags through __GFP_ZEROTAGS is irrelevant for most pages that will get mapped to user space through set_pte_at() later: set_pte_at() and friends will detect that the tags have not been initialized yet (PG_mte_tagged not set), and initialize them. However, for the huge zero folio, which will be mapped through a PMD marked as special, this initialization will not be performed, ending up exposing whatever tags were still set for the pages. The docs (Documentation/arch/arm64/memory-tagging-extension.rst) state that allocation tags are set to 0 when a page is first mapped to user space. That no longer holds with the huge zero folio when init_on_free is enabled. Fix it by decoupling __GFP_ZEROTAGS from __GFP_ZERO, passing to tag_clear_highpages() whether we want to also clear page content. Invert the meaning of the tag_clear_highpages() return value to have clearer semantics. Reproduced with the huge zero folio by modifying the check_buffer_fill arm64/mte selftest to use a 2 MiB area, after making sure that pages have a non-0 tag set when freeing (note that, during boot, we will not actually initialize tags, but only set KASAN_TAG_KERNEL in the page flags). $ ./check_buffer_fill 1..20 ... not ok 17 Check initial tags with private mapping, sync error mode and mmap memory not ok 18 Check initial tags with private mapping, sync error mode and mmap/mprotect memory ... This code needs more cleanups; we'll tackle that next, like decoupling __GFP_ZEROTAGS from __GFP_SKIP_KASAN. [akpm@linux-foundation.org: s/__GPF_ZERO/__GFP_ZERO/, per David] Link: https://lore.kernel.org/20260421-zerotags-v2-1-05cb1035482e@kernel.org Fixes: adfb6609c680 ("mm/huge_memory: initialise the tags of the huge zero folio") Signed-off-by: David Hildenbrand (Arm) Reviewed-by: Catalin Marinas Tested-by: Lance Yang Cc: Brendan Jackman Cc: Dev Jain Cc: Johannes Weiner Cc: Liam Howlett Cc: Lorenzo Stoakes (Oracle) Cc: Mark Brown Cc: Michal Hocko Cc: Mike Rapoport Cc: Ryan Roberts Cc: Suren Baghdasaryan Cc: Will Deacon Cc: Zi Yan Cc: Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman

mm/memory_hotplug: fix memory block reference leak on remove

2026-06-01T15:50:41+00:00

commit 93866f55f7e292fe3d47d36c9efe5ee10213a06b upstream. Patch series "mm: Fix memory block leaks and locking", v2. This series fixes two memory block device reference leaks and one locking issue around the per-memory_block hwpoison counter. This patch (of 2): remove_memory_blocks_and_altmaps() looks up each memory block with find_memory_block(), which acquires a reference to the memory block device. That reference is never dropped on this path, resulting in a leaked device reference when removing memory blocks and their altmaps. Drop the reference after retrieving mem->altmap and clearing mem->altmap, before removing the memory block device. Link: https://lore.kernel.org/20260428085219.1316047-1-songmuchun@bytedance.com Link: https://lore.kernel.org/20260428085219.1316047-2-songmuchun@bytedance.com Fixes: 6b8f0798b85a ("mm/memory_hotplug: split memmap_on_memory requests across memblocks") Signed-off-by: Muchun Song Acked-by: Oscar Salvador Acked-by: David Hildenbrand (Arm) Cc: Danilo Krummrich Cc: Greg Kroah-Hartman Cc: "Huang, Ying" Cc: Miaohe Lin Cc: Naoya Horiguchi Cc: "Rafael J. Wysocki" Cc: Vishal Verma Cc: Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman

mm: fix __vm_normal_page() to handle missing support for pmd_special()/pud_special()

2026-06-01T15:50:41+00:00

commit c0c6ccd9828c3a1950623b546fa57292a77b5c73 upstream. On x86 32-bit with THP enabled, zap_huge_pmd() is seen to generate a "WARNING: mm/memory.c:735 at __vm_normal_page+0x6a/0x7d", from the VM_WARN_ON_ONCE(is_zero_pfn(pfn) || is_huge_zero_pfn(pfn)); followed by "BUG: Bad rss-counter state"s, then later "BUG: Bad page state"s when reclaim gets to call shrink_huge_zero_folio_scan(). It's as if the _PAGE_SPECIAL bit never got set in the huge_zero pmd: and indeed, whereas pte_special() and pte_mkspecial() are subject to a dedicated CONFIG_ARCH_HAS_PTE_SPECIAL, pmd_special() and pmd_mkspecial() are subject to CONFIG_ARCH_SUPPORTS_PMD_PFNMAP, which is never enabled on any 32-bit architecture. While the problem was exposed through commit d80a9cb1a64a ("mm/huge_memory: add and use normal_or_softleaf_folio_pmd()"), it was an oversight in commit af38538801c6 ("mm/memory: factor out common code from vm_normal_page_*()") and would result in other problems: * huge zero folio accounted in smaps, pagemap (PAGE_IS_FILE) and numamaps as file-backed THP * folio_walk_start() returning the folio even without FW_ZEROPAGE set. Callers seem to tolerate that, though. ... and triggering the VM_WARN_ON_ONE(), although never reported so far. To fix it, teach vm_normal_page_pmd()/vm_normal_page_pud() to consider whether pmd_special/pud_special is actually implemented. Link: https://lore.kernel.org/20260430-pmd_special-v1-1-dbcbcfd72c20@kernel.org Fixes: af38538801c6 ("mm/memory: factor out common code from vm_normal_page_*()") Signed-off-by: David Hildenbrand (Arm) Reported-by: Hugh Dickins Closes: https://lore.kernel.org/r/74a75b59-2e13-3985-ee99-d5521f39df2a@google.com Reported-by: Bibo Mao Closes: https://lore.kernel.org/r/20260430041121.2839350-1-maobibo@loongson.cn Debugged-by: Hugh Dickins Reviewed-by: Lance Yang Tested-by: Bibo Mao Reviewed-by: Baolin Wang Reviewed-by: Oscar Salvador Reviewed-by: Lorenzo Stoakes Cc: Liam R. Howlett Cc: Michal Hocko Cc: Mike Rapoport Cc: Suren Baghdasaryan Cc: Vlastimil Babka Cc: Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman

mm/memory: fix spurious warning when unmapping device-private/exclusive pages

2026-06-01T15:50:41+00:00

commit be3f38d05cc5a7c3f13e51994c5dd043ab604d28 upstream. Device private and exclusive entries are only supported for anonymous folios. This condition is tested in __migrate_device_pages() and make_device_exclusive() using folio_test_anon(). However the unmap path tests this assumption using vma_is_anonymous(). This is wrong because whilst anonymous VMAs can only contain folios where folio_test_anon() is true the opposite relation does not hold. A folio for which folio_test_anon() is true does not imply vma_is_anonymous() is true. Such a condition can occur if for example a folio is part of a private filebacked mapping. In this case vma_is_anonymous() is false as the mapping is filebacked, but folio_test_anon() may be true, thus permitting devices to migrate the folio to device private memory. This can lead to the following spurious warnings during process teardown: [ 772.737706] ------------[ cut here ]------------ [ 772.739201] WARNING: mm/memory.c:1754 at unmap_page_range.cold+0x26/0x18a, CPU#17: hmm-tests/2041 [ 772.742050] Modules linked in: test_hmm nvidia_uvm(O) nvidia(O) [ 772.743959] CPU: 17 UID: 0 PID: 2041 Comm: hmm-tests Tainted: G W O 7.0.0+ #387 PREEMPT(full) [ 772.747104] Tainted: [W]=WARN, [O]=OOT_MODULE [ 772.748509] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.17.0-0-gb52ca86e094d-prebuilt.qemu.org 04/01/2014 [ 772.752117] RIP: 0010:unmap_page_range.cold+0x26/0x18a [ 772.753780] Code: 7e fe ff ff 48 89 4c 24 78 4c 89 44 24 38 e8 f2 ff b1 00 48 8b 4c 24 78 4c 8b 44 24 38 48 8b 44 24 18 48 83 78 48 00 74 04 90 <0f> 0b 90 48 89 ca b8 ff ff 37 00 48 c1 ea 03 48 c1 e0 2a 80 3c 02 [ 772.759602] RSP: 0018:ffff888112607550 EFLAGS: 00010286 [ 772.761310] RAX: ffff88811bbf4dc0 RBX: dffffc0000000000 RCX: ffffea03e9bfffd8 [ 772.763583] RDX: 1ffff1102377e9c1 RSI: 0000000000000008 RDI: ffff88811bbf4e08 [ 772.765914] RBP: 0000000000000006 R08: ffff8881059f7448 R09: ffffed10224c0e68 [ 772.768184] R10: ffff888112607347 R11: 0000000000000001 R12: 0000000000000001 [ 772.770461] R13: ffffea03e9bfffc0 R14: ffff888112607908 R15: ffffea03e9bfffc0 [ 772.772782] FS: 00007f327caa2780(0000) GS:ffff888427b7d000(0000) knlGS:0000000000000000 [ 772.775328] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 772.777187] CR2: 00007f327ca89000 CR3: 00000001994d5000 CR4: 00000000000006f0 [ 772.779135] Call Trace: [ 772.779792] [ 772.780317] ? dmirror_interval_invalidate+0x1a3/0x290 [test_hmm] [ 772.781873] ? vm_normal_page_pud+0x2b0/0x2b0 [ 772.782992] ? __rwlock_init+0x150/0x150 [ 772.784006] ? lock_release+0x216/0x2b0 [ 772.785008] ? __mmu_notifier_invalidate_range_start+0x505/0x6e0 [ 772.786522] ? lock_release+0x216/0x2b0 [ 772.787498] ? unmap_single_vma+0xb6/0x210 [ 772.788573] unmap_vmas+0x27d/0x520 [ 772.789506] ? unmap_single_vma+0x210/0x210 [ 772.790607] ? mas_update_gap.part.0+0x620/0x620 [ 772.791834] unmap_region+0x19e/0x350 [ 772.792769] ? remove_vma+0x130/0x130 [ 772.793684] ? mas_alloc_nodes+0x1f2/0x300 [ 772.794730] vms_complete_munmap_vmas+0x8c1/0xe20 [ 772.795926] ? unmap_region+0x350/0x350 [ 772.796917] do_vmi_align_munmap+0x36a/0x4e0 [ 772.798018] ? lock_release+0x216/0x2b0 [ 772.799024] ? vma_shrink+0x620/0x620 [ 772.799983] do_vmi_munmap+0x150/0x2c0 [ 772.800939] __vm_munmap+0x161/0x2c0 [ 772.801872] ? expand_downwards+0xd60/0xd60 [ 772.802948] ? clockevents_program_event+0x1ef/0x540 [ 772.804217] ? lock_release+0x216/0x2b0 [ 772.805158] __x64_sys_munmap+0x59/0x80 [ 772.805776] do_syscall_64+0xfc/0x670 [ 772.806336] ? irqentry_exit+0xda/0x580 [ 772.806976] entry_SYSCALL_64_after_hwframe+0x4b/0x53 [ 772.807772] RIP: 0033:0x7f327cbb2717 [ 772.808323] Code: 73 01 c3 48 8b 0d f9 76 0d 00 f7 d8 64 89 01 48 83 c8 ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 b8 0b 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d c9 76 0d 00 f7 d8 64 89 01 48 [ 772.811337] RSP: 002b:00007ffde7f57d38 EFLAGS: 00000202 ORIG_RAX: 000000000000000b [ 772.812564] RAX: ffffffffffffffda RBX: 00007f327cc9c000 RCX: 00007f327cbb2717 [ 772.813733] RDX: 0000000000000000 RSI: 0000000000400000 RDI: 00007f327c289000 [ 772.814867] RBP: 0000000000421360 R08: 000000000000001a R09: 0000000000000000 [ 772.815991] R10: 0000000000000003 R11: 0000000000000202 R12: 00007ffde7f57d74 [ 772.817121] R13: 00007f327c689010 R14: 0000000000100000 R15: 00007f327c289000 [ 772.818272] [ 772.818614] irq event stamp: 0 [ 772.819159] hardirqs last enabled at (0): [<0000000000000000>] 0x0 [ 772.820174] hardirqs last disabled at (0): [] copy_process+0x19f3/0x6440 [ 772.821511] softirqs last enabled at (0): [] copy_process+0x1a40/0x6440 [ 772.822869] softirqs last disabled at (0): [<0000000000000000>] 0x0 [ 772.823871] ---[ end trace 0000000000000000 ]--- Fix this by using the same check for folio_test_anon() in zap_nonpresent_ptes(). Also add a hmm-test case for this. Link: https://lore.kernel.org/20260501065116.2057242-1-apopple@nvidia.com Fixes: 999dad824c39 ("mm/shmem: persist uffd-wp bit across zapping for file-backed") Signed-off-by: Alistair Popple Reported-by: Arsen Arsenović Reviewed-by: Balbir Singh Cc: David Hildenbrand Cc: Jason Gunthorpe Cc: John Hubbard Cc: Leon Romanovsky Cc: Liam R. Howlett Cc: Lorenzo Stoakes Cc: Peter Xu Cc: Matthew Brost Cc: Michal Hocko Cc: Mike Rapoport Cc: Shuah Khan Cc: Suren Baghdasaryan Cc: Thomas Hellström Cc: Vlastimil Babka Cc: Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman