laptop-kernel/mm, branch master

mm: don't schedule deferred kernel page table freeing while booting

2026-10-06T23:44:18Z

Booting with a boot-time function tracer and a filter, for example ftrace=function ftrace_filter=pud_free_pmd_page panics on 7.3-rc4 as soon as the tracer starts: [ 23.531178] Starting tracer 'function' [ 23.675800] Oops: general protection fault, probably for non-canonical address 0xdffffc0000000038: 0000 [#1] SMP KASAN NOPTI [ 23.819917] KASAN: null-ptr-deref in range [0x00000000000001c0-0x00000000000001c7] [ 23.964025] CPU: 0 UID: 0 PID: 0 Comm: swapper Not tainted 7.3.0-rc4-fe2ec83746e5-with-fixes-v2+ #195 PREEMPT(undef) [ 24.252248] RIP: 0010:__queue_work+0xab/0xf00 [ 25.981629] Call Trace: [ 26.125727] [ 26.413912] ? pagetable_free_kernel+0x20/0x120 [ 26.990283] queue_work_on+0x97/0xf0 [ 27.134382] __cpa_collapse_large_pages+0x501/0x6f0 [ 27.566662] cpa_flush+0x394/0x620 [ 27.998953] change_page_attr_set_clr+0x321/0x4a0 [ 29.151729] set_memory_rox+0xa2/0xf0 [ 29.584018] create_trampoline+0x431/0x6f0 ... [ 44.343347] Kernel panic - not syncing: Attempted to kill the idle task! The boot-time tracer is started from early_trace_init(), which runs before workqueue_init_early(). Making its trampoline read-only splits a large page, and CPA collapses it again right away. The split table has been a kernel page table since commit 9e4a3ec3411b ("x86/mm/pat: Allocate split page tables as kernel page tables"), so the collapse frees it through pagetable_free_kernel(), which queues work on system_percpu_wq - still NULL at that point. That commit is correct in itself; it only lets CPA reach pagetable_free_kernel() before the workqueue that function relies on exists. Keep putting the table on the list, but don't schedule the work while the system is still booting. A core_initcall schedules it once to free whatever was queued by then. Link: https://lore.kernel.org/20260925050647.86913-1-mikhail.v.gavrilov@gmail.com Link: https://lore.kernel.org/20260924064321.23787-1-mikhail.v.gavrilov@gmail.com Fixes: 9e4a3ec3411b ("x86/mm/pat: Allocate split page tables as kernel page tables") Signed-off-by: Mikhail Gavrilov Signed-off-by: Andrew Morton Suggested-by: David Hildenbrand (Arm) Suggested-by: Lorenzo Stoakes (ARM) Reviewed-by: Andrew Morton Reviewed-by: David Hildenbrand (Arm) Reviewed-by: Lorenzo Stoakes (ARM) Reviewed-by: Jose A. Perez de Azpillaga Tested-by: Jose A. Perez de Azpillaga Cc: Dave Hansen Cc: Liam R. Howlett Cc: Vlastimil Babka Cc: Mike Rapoport Cc: Suren Baghdasaryan Cc: Michal Hocko Cc: Vishal Moola (Oracle) Cc: Ingo Molnar Cc: Lu Baolu Cc: Jason Gunthorpe Cc: Steven Rostedt Cc:

mm/mremap: fix locked_vm leak by splitting VMA for MREMAP_DONTUNMAP

2026-10-06T23:44:17Z

The MREMAP_DONTUNMAP feature is highly unusual in that it permits mremap() operations that keep the original VMA in place. Historically this has led to a lot of bugs where non-obvious interactions occur between existing mremap() operations and the original VMA. Fix another of these - partial copies. The long-standing mremap() partial VMA logic has the baked-in assumption that the originating VMA is unmapped and thus moved. However MREMAP_DONTUNMAP defeats this by performing a partial copy instead since it keeps the source VMA around. An mremap(..., MREMAP_DONTUNMAP) operation disallows resizing of the VMA, but the operation can be performed partially: |-----------------| | | | v <------> <------> .new_sz. new_sz |--.------.--| |------| | .source. | | dest | |--.------.--| |------| <------------> old_sz The page tables in the specified range are moved, but the original VMA is kept intact. This interacts poorly with mlock()'d VMAs, as the VMA_LOCKED_BIT flag is cleared for the entire source VMA and set for the entire destination VMA. This results in an mm->locked_vm leak as the change is therefore not accounted correctly. The clear solution here is to make the portion of the source VMA which is mremap()'d distinct from the rest of it, a.k.a. split it. Therefore resolve this issue by splitting it ahead of the rest of the mremap() operation if the VMA is mlock()'d. This is valid, as the source VMA will lose its VMA_LOCKED_BIT flag, so if a partial remap it will become distinct from the rest of the VMA. In order to make this change re-expose split_vma() in vma.h for CONFIG_MMU (nommu doesn't compile mremap.c and uses a static helper instead). Finally, update the sys_map_count check to account for this case. Note that the early check does not use needs_pre_split() - this is because the VMA has not been looked up by this point, so be conservative and assume that the VMA is mlock()'d in this case for the purposes of the sys_map_count check. Link: https://lore.kernel.org/20260930-fix-dontunmap-partial-self-merge-v2-2-f388985a0f0a@kernel.org Fixes: e346b3813067 ("mm/mremap: add MREMAP_DONTUNMAP to mremap()") Signed-off-by: Lorenzo Stoakes (ARM) Signed-off-by: Andrew Morton Reviewed-by: Pedro Falcato Acked-by: Kiryl Shutsemau (Meta) Reviewed-by: Jose A. Perez de Azpillaga Tested-by: Anirudh Srinivasan Cc: Liam R. Howlett Cc: Vlastimil Babka Cc: Jann Horn Cc: Brian Geffon Cc: Minchan Kim Cc:

mm/mremap: fix locked_vm leak from MREMAP_DONTUNMAP self-merge

2026-10-06T23:44:17Z

Patch series "mm/mremap: fix two issues with MREMAP_DONTUNMAP", v2. The MREMAP_DONTUNMAP feature is highly unusual in that it permits mremap() operations that keep the original VMA in place. Historically this has led to a lot of bugs where non-obvious interactions occur between existing mremap() operations and the original VMA. Commit 397432cab17b ("mm/mremap: account mm->locked_vm correctly for MREMAP_DONTUNMAP") fixed an accidentally introduced bug around mm->locked_vm accounting, but this wasn't the only issue. And thus history repeats itself, as it turns out that mm->locked_vm accounting is broken by MREMAP_DONTUNMAP yet again by two further cases, and has been broken ever since the feature was introduced. Both relate to the fact that VMA_LOCKED_BIT is cleared on the source VMA (it has to be as all page tables are moved): 1. If an unfaulted VMA_LOCKONFAULT_BIT anonymous VMA self-merges it clears the VMA_LOCKED_BIT flag and permanently leaks mm->locked_vm pages. 2. If a partial mremap() is performed on a locked VMA there is a leak equal to the number of pages not copied. (Both for MREMAP_DONTUNMAP operations only) Both issues can be fixed by treating the source range as distinct from the destination range, which is the definition of what MREMAP_DONTUNMAP does so is appropriate. In case 1, simply disallow the self-merge, keeping adjacent source and destination VMAs distinct. In case 2, split the source range ahead of time if the VMA is mlock()'d, so accounting is always correct. Both changes were tested locally and confirmed to fix the issues. For the purposes of a backport, the fixes are kept distinct, a follow-up series can add self-tests. This patch (of 2): The MREMAP_DONTUNMAP feature is highly unusual in that it permits mremap() operations that keep the original VMA in place. Historically this has led to a lot of bugs where non-obvious interactions occur between existing mremap() operations and the original VMA. Fix another of these - self-merge. Self-merge occurs when a VMA is moved in front of or behind itself and the attributes of the VMA permit such a merge. Practically this can only happen for unfaulted anonymous VMAs due to the page offset equality requirement for merge: |------------| | | | v |...........||-----------||...........| | || unfaulted || | |...........||-----------||...........| ^ | | | |------------| This becomes problematic if the VMA is configured by the user to mlock-on-fault, i.e. the VMA_LOCKED_BIT, VMA_LOCKONFAULT_BIT VMA flags are set. MREMAP_DONTUNMAP clears mlock flags for the source VMA and maintains them for the destination VMA. Self-merge makes this impossible (there is only one VMA) and incorrectly clears the destination VMA's mlock flags. This causes a leak in mm->locked_vm as clearing this flag does not decrement the counter and the VMA no longer has VMA_LOCKED_BIT set so it is not decremented on unmap. Resolve this by simply disallowing a self-merge in this case - the source and destination VMAs are kept distinct and then are able to have distinct mlock() flags. Update dontunmap_complete() to make the now-redundant self-merge check a VM_WARN_ON_ONCE() instead to guard against future regressions. Also update the VMA userland tests to reflect the change. Link: https://lore.kernel.org/20260930-fix-dontunmap-partial-self-merge-v2-0-f388985a0f0a@kernel.org Link: https://lore.kernel.org/20260930-fix-dontunmap-partial-self-merge-v2-1-f388985a0f0a@kernel.org Fixes: e346b3813067 ("mm/mremap: add MREMAP_DONTUNMAP to mremap()") Signed-off-by: Lorenzo Stoakes (ARM) Signed-off-by: Andrew Morton Reviewed-by: Pedro Falcato Acked-by: Kiryl Shutsemau (Meta) Reviewed-by: Jose A. Perez de Azpillaga Tested-by: Anirudh Srinivasan Cc: Liam R. Howlett Cc: Vlastimil Babka Cc: Jann Horn Cc: Brian Geffon Cc: Minchan Kim Cc:

Merge tag 'slab-for-7.3-rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/mm/slab

2026-10-02T17:51:34Z

Pull slab fixes from Vlastimil Babka: - Stable fix for a potential deadlock in kfree_rcu() when called from set_cpus_allowed_force() (Harry Yoo) - MAINTAINERS update of the slab.git URL * tag 'slab-for-7.3-rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/mm/slab: mm/slab: do not wake up kswapd in __kfree_rcu_sheaf() MAINTAINERS: update slab.git URL

Merge tag 'mm-hotfixes-stable-2026-09-27-19-12' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

2026-09-29T03:11:31Z

Pull MM fixes from Andrew Morton: - Fix module loading incorrectly returning success after alloc_tag codetag setup failed - Restore MADV_COLLAPSE semantics for shmem so forced collapse ignores the shmem THP/mTHP sysfs settings - Make alloc_tag UAPI structure padding explicit - Fix DAMON schemes unexpectedly stopping after quotas are disabled through the online parameter update interface - Fix a false SW_TAGS KASAN invalid-access report when freeing vmapped task stacks - Split the MEMORY MANAGEMENT - MEMORY POLICY AND MIGRATION MAINTAINERS entry into separate MIGRATION and NUMA PLACEMENT entries - Move memory tiering maintenance under NUMA PLACEMENT - Add Gregory Price as a NUMA PLACEMENT co-maintainer - Add Heming Zhao as an ocfs2 reviewer - Fix mmap_prepare() state being copied onto a merged VMA rather than only onto a newly allocated VMA * tag 'mm-hotfixes-stable-2026-09-27-19-12' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: mm/vma: predicate setting mmap_prepare VMA fields on new vma alloc MAINTAINERS: add Heming Zhao as ocfs2 reviewer MAINTAINERS: make Gregory a co-maintainer of MEMORY MANAGEMENT - NUMA PLACEMENT MAINTAINERS: move memory tiering under MEMORY MANAGEMENT - NUMA PLACEMENT MAINTAINERS: split up MEMORY MANAGEMENT - MEMORY POLICY AND MIGRATION kasan: unpoison task stack below watermark only in generic mode mm/damon/core: don't skip damos_adjust_quota() while esz is not zero alloc_tag: avoid implicit padding in uapi mm: shmem: ignore sysfs configs for shmem forced collapse module: fix lost error code from codetag_load_module()

mm/vma: predicate setting mmap_prepare VMA fields on new vma alloc

2026-09-26T20:55:11Z

It only makes sense to manipulate VMA fields if a new VMA was allocated, rather than merged. VMA merging does not compare vm_ops or vm_private_data, so a merged VMA keeps its own, which is also what the legacy f_op->mmap path does since it never touches an existing VMA. Currently, these fields will get overwritten by whatever state is established in the mmap_prepare hook, and if the VMA was merged, vm_ops->mapped will not have been called, so this could destructively clear existing state without replacing it with anything valid. There is an implicit requirement that vm_private_data and vm_ops are fungible across VMAs which means that losing the 'new' state is fine. However in this case the 'old' state is being overwritten by potentially invalid 'new' state, so this must be rectified. Additionally constify have_mmap_prepare while here. All existing in-tree users either derive state from the file or are unmergeable due to VMA flags, so this has no direct impact. Link: https://lore.kernel.org/20260923-fix-mmap-prepare-overwrite-v1-1-3b3f1bfcdf5e@kernel.org Fixes: c84bf6dd2b83 ("mm: introduce new .mmap_prepare() file callback") Signed-off-by: Lorenzo Stoakes (ARM) Signed-off-by: Andrew Morton Reviewed-by: Suren Baghdasaryan Reviewed-by: Gregory Price (Meta) Acked-by: Zi Yan Acked-by: Vlastimil Babka (SUSE) Cc: Liam R. Howlett Cc: Jann Horn Cc: Pedro Falcato Cc:

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:

mm/damon/core: don't skip damos_adjust_quota() while esz is not zero

2026-09-26T20:55:10Z

DAMOS could unexpectedly stop working when a user disables quota using the online parameters commit feature. Fix it by correcting a wrong quota unset check in damos_adjust_quota(). DAMON users could disable all quotas by unsetting time and size quotas, and removing all quota goals. The intention of disabling quotas would be making DAMOS run at full speed. When such quota disabled setup is detected, damos_adjust_quota() skips all its work. The skipped works include effective size quota (damos_quota->esz) updates and charged quota amount (damos_quota->charged_sz) resets. The intention is to avoid doing unnecessary work when quotas are disabled. However, users could do the setup while effective size quota is non-zero, by doing the disabling with the online DAMON parameters commit feature. In this case, because the effective size quota exists, DAMOS will keep working with the quota until it is fully charged. After the effective quota is fully charged, the charged quota amount (damos_quota->charged_sz) cannot be reset because damos_adjust_quota() skips it. Then, DAMOS stops working until the quota is newly set or DAMON is entirely restarted. The problem happens because damos_adjust_quota() assumes the user setup for disabling quota immediately disabled it. In reality, the quota is still working until the effective size quota is also updated to zero. Other logic for catching that uses damos_quota_is_set(), which understands the fact and therefore checks the effective size quota in addition to the user setup. Fix the issue by using damos_quota_is_set() in damos_adjust_quota() to determine if its works should be skipped. The user impact is a non-deterministic and unexpected DAMOS stop behavior. That is, users would disable quotas using the online parameters commit feature, expecting DAMOS will run at full speed. However, depending on the timing, the setup can be updated while the effective size quota is non-zero. Due to the above mentioned internal mechanism, DAMOS stops working instead of running at full speed. It is unexpected behavior. It is also non-deterministic because sometimes the setup is done when the effective size quota is zero, depending on the timing. It doesn't cause critical issues like crashes or leaks. Users can simply set a reasonable quota again, or restart DAMON. But definitely it is an unexpected and non-deterministic behavior that makes it difficult to reliably use. Also investigating the root cause of the behavior would be quite difficult. Link: https://lore.kernel.org/20260916135020.86483-1-sj@kernel.org Fixes: da87878010e5 ("mm/damon/sysfs: support online inputs update") Signed-off-by: SJ Park Signed-off-by: Andrew Morton Reviewed-by: Kunwu Chan Cc: # 5.19.x

mm: shmem: ignore sysfs configs for shmem forced collapse

2026-09-26T20:55:09Z

According to Documentation/mm/transhuge.rst, MADV_COLLAPSE is expected to ignore any THP or mTHP interface settings. However, after commit 26c7d8413aaf ("mm: thp: support "THPeligible" semantics for mTHP with anonymous shmem"), performing MADV_COLLAPSE on shmem will depend on /sys/.../hugepages-2048kB/shmem_enabled being set to "inherit" (although that is the default), which can cause MADV_COLLAPSE to fail unexpectedly. This could cause a userspace-visible performance regression. Fix this by returning the result of shmem_huge_global_enabled() directly when MADV_COLLAPSE is requested, allowing PMD-order collapse while ignoring shmem THP/mTHP settings. Link: https://lore.kernel.org/063f655b4d6c4234f3aa27ed6ecab10283ecb880.1789351825.git.baolin.wang@linux.alibaba.com Fixes: 26c7d8413aaf ("mm: thp: support "THPeligible" semantics for mTHP with anonymous shmem") Signed-off-by: Baolin Wang Signed-off-by: Andrew Morton Reported-by: Kiryl Shutsemau (Meta) Closes: https://lore.kernel.org/all/20260908125105.1510704-7-kirill@shutemov.name/ Reviewed-by: Kiryl Shutsemau (Meta) Acked-by: Zi Yan Reviewed-by: Lance Yang Reviewed-by: Barry Song Acked-by: Qi Zheng Acked-by: David Hildenbrand (Arm) Reviewed-by: Lorenzo Stoakes (ARM) Cc: Dev Jain Cc: Hugh Dickins Cc: Liam R. Howlett Cc: Ryan Roberts Cc:

Merge tag 'fixes-2026-09-24' of git://git.kernel.org/pub/scm/linux/kernel/git/mm/memblock

2026-09-24T13:16:19Z

Pull memblock fix from Mike Rapoport: "The rework of HugeTLB bootmem allocation forgot to add the name for a new RSV_HUGETLB flag for proper display in debugfs. Add the flag name now" * tag 'fixes-2026-09-24' of git://git.kernel.org/pub/scm/linux/kernel/git/mm/memblock: mm: memblock: add missing HugeTLB flag name