kernel/linux.git/fs/aio.c, branch v7.1-rc5

fs: aio: reject partial mremap to avoid Null-pointer-dereference error

2026-04-23T22:34:59+00:00

[BUG] Recently, our internal syzkaller testing uncovered a null pointer dereference issue: BUG: kernel NULL pointer dereference, address: 0000000000000000 ... [ 51.111664] filemap_read_folio+0x25/0xe0 [ 51.112410] filemap_fault+0xad7/0x1250 [ 51.113112] __do_fault+0x4b/0x460 [ 51.113699] do_pte_missing+0x5bc/0x1db0 [ 51.114250] ? __pte_offset_map+0x23/0x170 [ 51.114822] __handle_mm_fault+0x9f8/0x1680 ... Crash analysis showed the file involved was an AIO ring file. The phenomenon triggered is the same as the issue described in [1]. [CAUSE] Consider the following scenario: userspace sets up an AIO context via io_setup(), which creates a VMA covering the entire ring buffer. Then userspace calls mremap() with the AIO ring address as the source, a smaller old_len (less than the full ring size), MREMAP_MAYMOVE set, and without MREMAP_DONTUNMAP. The kernel will relocate the requested portion to a new destination address. During this move, __split_vma() splits the original AIO ring VMA. The requested portion is unmapped from the source and re-established at the destination, while the remainder stays at the original source address as an orphan VMA. The aio_ring_mremap() callback fires on the new destination VMA, updating ctx->mmap_base to the destination address. But the callback is unaware that only a partial region was moved and that an orphan VMA still exists at the source: source(AIO): +-------------------+---------------------+ | moved to dest | orphan VMA (AIO) | +-------------------+---------------------+ A A+partial_len A+ctx->mmap_size dest: +-------------------+ | moved VMA (AIO) | +-------------------+ B B+partial_len Later, io_destroy() calls vm_munmap(ctx->mmap_base, ctx->mmap_size), which unmaps the destination. This not only fails to unmap the orphan VMA at the source, but also overshoots the destination VMA and may unmap unrelated mappings adjacent to it! After put_aio_ring_file() calls truncate_setsize() to remove all pages from the pagecache, any subsequent access to the orphan VMA triggers filemap_fault(), which calls a_ops->read_folio(). Since aio does not implement read_folio, this results in a NULL pointer dereference. [FIX] Note that expanding mremap (new_len > old_len) is already rejected because AIO ring VMAs are created with VM_DONTEXPAND. The only problematic case is a partial move where "old_len == new_len" but both are smaller than the full ring size. Fix this by checking in aio_ring_mremap() that the new VMA covers the entire ring. This ensures the AIO ring is always moved as a whole, preventing orphan VMAs and the subsequent crash. [1]: https://lore.kernel.org/all/20260413010814.548568-1-wozizhi@huawei.com/ Signed-off-by: Zizhi Wo Link: https://patch.msgid.link/20260418060634.3713620-1-wozizhi@huaweicloud.com Reviewed-by: Jan Kara Signed-off-by: Christian Brauner

fs: aio: set VMA_DONTCOPY_BIT in mmap to fix NULL-pointer-dereference error

2026-04-23T22:34:58+00:00

[BUG] Recently, our internal syzkaller testing uncovered a null pointer dereference issue: BUG: kernel NULL pointer dereference, address: 0000000000000000 ... [ 51.111664] filemap_read_folio+0x25/0xe0 [ 51.112410] filemap_fault+0xad7/0x1250 [ 51.113112] __do_fault+0x4b/0x460 [ 51.113699] do_pte_missing+0x5bc/0x1db0 [ 51.114250] ? __pte_offset_map+0x23/0x170 [ 51.114822] __handle_mm_fault+0x9f8/0x1680 [ 51.115408] handle_mm_fault+0x24c/0x570 [ 51.115958] do_user_addr_fault+0x226/0xa50 ... Crash analysis showed the file involved was an AIO ring file. [CAUSE] PARENT process CHILD process t=0 io_setup(1, &ctx) [access ctx addr] fork() io_destroy vm_munmap // not affect child vma percpu_ref_put ... put_aio_ring_file t=1 [access ctx addr] // pagefault ... __do_fault filemap_fault max_idx = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE) t=2 truncate_setsize truncate_pagecache t=3 filemap_get_folio // no folio, create folio __filemap_get_folio(..., FGP_CREAT, ...) // page_not_uptodate filemap_read_folio(file, mapping->a_ops->read_folio, folio) // oops! At t=0, the parent process calls io_setup and then fork. The child process gets its own VMA but without any PTEs. The parent then calls io_destroy. Before i_size is truncated to 0, at t=1 the child process accesses this AIO ctx address and triggers a pagefault. After the max_idx check passes, at t=2 the parent calls truncate_setsize and truncate_pagecache. At t=3 the child fails to obtain the folio, falls into the "page_not_uptodate" path, and hits this problem because AIO does not implement "read_folio". [Fix] Fix this by marking the AIO ring buffer VMA with VM_DONTCOPY so that fork()'s dup_mmap() skips it entirely. This is the correct semantic because: 1) The child's ioctx_table is already reset to NULL by mm_init_aio() during fork(), so the child has no AIO context and no way to perform any AIO operations on this mapping. 2) The AIO ring VMA is only meaningful in conjunction with its associated kioctx, which is never inherited across fork(). So child process with no AIO context has no legitimate reason to access the ring buffer. Delivering SIGSEGV on such an erroneous access is preferable to a kernel crash. Signed-off-by: Zizhi Wo Link: https://patch.msgid.link/20260413010814.548568-1-wozizhi@huawei.com Reviewed-by: Jan Kara Signed-off-by: Christian Brauner

aio: Stop using i_private_data and i_private_lock

2026-03-26T14:03:30+00:00

Instead of using i_private_data and i_private_lock, just create aio inodes with appropriate necessary fields. Reviewed-by: Christoph Hellwig Signed-off-by: Jan Kara Link: https://patch.msgid.link/20260326095354.16340-67-jack@suse.cz Tested-by: syzbot@syzkaller.appspotmail.com Signed-off-by: Christian Brauner

Convert more 'alloc_obj' cases to default GFP_KERNEL arguments

2026-02-22T04:03:00+00:00

This converts some of the visually simpler cases that have been split over multiple lines. I only did the ones that are easy to verify the resulting diff by having just that final GFP_KERNEL argument on the next line. Somebody should probably do a proper coccinelle script for this, but for me the trivial script actually resulted in an assertion failure in the middle of the script. I probably had made it a bit _too_ trivial. So after fighting that far a while I decided to just do some of the syntactically simpler cases with variations of the previous 'sed' scripts. The more syntactically complex multi-line cases would mostly really want whitespace cleanup anyway. Signed-off-by: Linus Torvalds

Convert 'alloc_flex' family to use the new default GFP_KERNEL argument

2026-02-22T01:09:51+00:00

This is the exact same thing as the 'alloc_obj()' version, only much smaller because there are a lot fewer users of the *alloc_flex() interface. As with alloc_obj() version, this was done entirely with mindless brute force, using the same script, except using 'flex' in the pattern rather than 'objs*'. Signed-off-by: Linus Torvalds

treewide: Replace kmalloc with kmalloc_obj for non-scalar types

2026-02-21T09:02:28+00:00

This is the result of running the Coccinelle script from scripts/coccinelle/api/kmalloc_objs.cocci. The script is designed to avoid scalar types (which need careful case-by-case checking), and instead replace kmalloc-family calls that allocate struct or union object instances: Single allocations: kmalloc(sizeof(TYPE), ...) are replaced with: kmalloc_obj(TYPE, ...) Array allocations: kmalloc_array(COUNT, sizeof(TYPE), ...) are replaced with: kmalloc_objs(TYPE, COUNT, ...) Flex array allocations: kmalloc(struct_size(PTR, FAM, COUNT), ...) are replaced with: kmalloc_flex(*PTR, FAM, COUNT, ...) (where TYPE may also be *VAR) The resulting allocations no longer return "void *", instead returning "TYPE *". Signed-off-by: Kees Cook

mm: update all remaining mmap_prepare users to use vma_flags_t

2026-02-12T23:42:58+00:00

We will be shortly removing the vm_flags_t field from vm_area_desc so we need to update all mmap_prepare users to only use the dessc->vma_flags field. This patch achieves that and makes all ancillary changes required to make this possible. This lays the groundwork for future work to eliminate the use of vm_flags_t in vm_area_desc altogether and more broadly throughout the kernel. While we're here, we take the opportunity to replace VM_REMAP_FLAGS with VMA_REMAP_FLAGS, the vma_flags_t equivalent. No functional changes intended. Link: https://lkml.kernel.org/r/fb1f55323799f09fe6a36865b31550c9ec67c225.1769097829.git.lorenzo.stoakes@oracle.com Signed-off-by: Lorenzo Stoakes Acked-by: Damien Le Moal [zonefs] Acked-by: "Darrick J. Wong" Acked-by: Pedro Falcato Cc: Baolin Wang Cc: Barry Song Cc: David Hildenbrand Cc: Dev Jain Cc: Jason Gunthorpe Cc: Liam Howlett Cc: Suren Baghdasaryan Cc: Vlastimil Babka Cc: Zi Yan Cc: Jarkko Sakkinen Cc: Yury Norov Cc: Chris Mason Signed-off-by: Andrew Morton

aio: use credential guards

2025-11-04T11:36:33+00:00

Use credential guards for scoped credential override with automatic restoration on scope exit. Link: https://patch.msgid.link/20251103-work-creds-guards-simple-v1-2-a3e156839e7f@kernel.org Reviewed-by: Amir Goldstein Signed-off-by: Christian Brauner

Merge tag 'mm-stable-2025-10-01-19-00' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

2025-10-03T01:18:33+00:00

Pull MM updates from Andrew Morton: - "mm, swap: improve cluster scan strategy" from Kairui Song improves performance and reduces the failure rate of swap cluster allocation - "support large align and nid in Rust allocators" from Vitaly Wool permits Rust allocators to set NUMA node and large alignment when perforning slub and vmalloc reallocs - "mm/damon/vaddr: support stat-purpose DAMOS" from Yueyang Pan extend DAMOS_STAT's handling of the DAMON operations sets for virtual address spaces for ops-level DAMOS filters - "execute PROCMAP_QUERY ioctl under per-vma lock" from Suren Baghdasaryan reduces mmap_lock contention during reads of /proc/pid/maps - "mm/mincore: minor clean up for swap cache checking" from Kairui Song performs some cleanup in the swap code - "mm: vm_normal_page*() improvements" from David Hildenbrand provides code cleanup in the pagemap code - "add persistent huge zero folio support" from Pankaj Raghav provides a block layer speedup by optionalls making the huge_zero_pagepersistent, instead of releasing it when its refcount falls to zero - "kho: fixes and cleanups" from Mike Rapoport adds a few touchups to the recently added Kexec Handover feature - "mm: make mm->flags a bitmap and 64-bit on all arches" from Lorenzo Stoakes turns mm_struct.flags into a bitmap. To end the constant struggle with space shortage on 32-bit conflicting with 64-bit's needs - "mm/swapfile.c and swap.h cleanup" from Chris Li cleans up some swap code - "selftests/mm: Fix false positives and skip unsupported tests" from Donet Tom fixes a few things in our selftests code - "prctl: extend PR_SET_THP_DISABLE to only provide THPs when advised" from David Hildenbrand "allows individual processes to opt-out of THP=always into THP=madvise, without affecting other workloads on the system". It's a long story - the [1/N] changelog spells out the considerations - "Add and use memdesc_flags_t" from Matthew Wilcox gets us started on the memdesc project. Please see https://kernelnewbies.org/MatthewWilcox/Memdescs and https://blogs.oracle.com/linux/post/introducing-memdesc - "Tiny optimization for large read operations" from Chi Zhiling improves the efficiency of the pagecache read path - "Better split_huge_page_test result check" from Zi Yan improves our folio splitting selftest code - "test that rmap behaves as expected" from Wei Yang adds some rmap selftests - "remove write_cache_pages()" from Christoph Hellwig removes that function and converts its two remaining callers - "selftests/mm: uffd-stress fixes" from Dev Jain fixes some UFFD selftests issues - "introduce kernel file mapped folios" from Boris Burkov introduces the concept of "kernel file pages". Using these permits btrfs to account its metadata pages to the root cgroup, rather than to the cgroups of random inappropriate tasks - "mm/pageblock: improve readability of some pageblock handling" from Wei Yang provides some readability improvements to the page allocator code - "mm/damon: support ARM32 with LPAE" from SeongJae Park teaches DAMON to understand arm32 highmem - "tools: testing: Use existing atomic.h for vma/maple tests" from Brendan Jackman performs some code cleanups and deduplication under tools/testing/ - "maple_tree: Fix testing for 32bit compiles" from Liam Howlett fixes a couple of 32-bit issues in tools/testing/radix-tree.c - "kasan: unify kasan_enabled() and remove arch-specific implementations" from Sabyrzhan Tasbolatov moves KASAN arch-specific initialization code into a common arch-neutral implementation - "mm: remove zpool" from Johannes Weiner removes zspool - an indirection layer which now only redirects to a single thing (zsmalloc) - "mm: task_stack: Stack handling cleanups" from Pasha Tatashin makes a couple of cleanups in the fork code - "mm: remove nth_page()" from David Hildenbrand makes rather a lot of adjustments at various nth_page() callsites, eventually permitting the removal of that undesirable helper function - "introduce kasan.write_only option in hw-tags" from Yeoreum Yun creates a KASAN read-only mode for ARM, using that architecture's memory tagging feature. It is felt that a read-only mode KASAN is suitable for use in production systems rather than debug-only - "mm: hugetlb: cleanup hugetlb folio allocation" from Kefeng Wang does some tidying in the hugetlb folio allocation code - "mm: establish const-correctness for pointer parameters" from Max Kellermann makes quite a number of the MM API functions more accurate about the constness of their arguments. This was getting in the way of subsystems (in this case CEPH) when they attempt to improving their own const/non-const accuracy - "Cleanup free_pages() misuse" from Vishal Moola fixes a number of code sites which were confused over when to use free_pages() vs __free_pages() - "Add Rust abstraction for Maple Trees" from Alice Ryhl makes the mapletree code accessible to Rust. Required by nouveau and by its forthcoming successor: the new Rust Nova driver - "selftests/mm: split_huge_page_test: split_pte_mapped_thp improvements" from David Hildenbrand adds a fix and some cleanups to the thp selftesting code - "mm, swap: introduce swap table as swap cache (phase I)" from Chris Li and Kairui Song is the first step along the path to implementing "swap tables" - a new approach to swap allocation and state tracking which is expected to yield speed and space improvements. This patchset itself yields a 5-20% performance benefit in some situations - "Some ptdesc cleanups" from Matthew Wilcox utilizes the new memdesc layer to clean up the ptdesc code a little - "Fix va_high_addr_switch.sh test failure" from Chunyu Hu fixes some issues in our 5-level pagetable selftesting code - "Minor fixes for memory allocation profiling" from Suren Baghdasaryan addresses a couple of minor issues in relatively new memory allocation profiling feature - "Small cleanups" from Matthew Wilcox has a few cleanups in preparation for more memdesc work - "mm/damon: add addr_unit for DAMON_LRU_SORT and DAMON_RECLAIM" from Quanmin Yan makes some changes to DAMON in furtherance of supporting arm highmem - "selftests/mm: Add -Wunreachable-code and fix warnings" from Muhammad Anjum adds that compiler check to selftests code and fixes the fallout, by removing dead code - "Improvements to Victim Process Thawing and OOM Reaper Traversal Order" from zhongjinji makes a number of improvements in the OOM killer: mainly thawing a more appropriate group of victim threads so they can release resources - "mm/damon: misc fixups and improvements for 6.18" from SeongJae Park is a bunch of small and unrelated fixups for DAMON - "mm/damon: define and use DAMON initialization check function" from SeongJae Park implement reliability and maintainability improvements to a recently-added bug fix - "mm/damon/stat: expose auto-tuned intervals and non-idle ages" from SeongJae Park provides additional transparency to userspace clients of the DAMON_STAT information - "Expand scope of khugepaged anonymous collapse" from Dev Jain removes some constraints on khubepaged's collapsing of anon VMAs. It also increases the success rate of MADV_COLLAPSE against an anon vma - "mm: do not assume file == vma->vm_file in compat_vma_mmap_prepare()" from Lorenzo Stoakes moves us further towards removal of file_operations.mmap(). This patchset concentrates upon clearing up the treatment of stacked filesystems - "mm: Improve mlock tracking for large folios" from Kiryl Shutsemau provides some fixes and improvements to mlock's tracking of large folios. /proc/meminfo's "Mlocked" field became more accurate - "mm/ksm: Fix incorrect accounting of KSM counters during fork" from Donet Tom fixes several user-visible KSM stats inaccuracies across forks and adds selftest code to verify these counters - "mm_slot: fix the usage of mm_slot_entry" from Wei Yang addresses some potential but presently benign issues in KSM's mm_slot handling * tag 'mm-stable-2025-10-01-19-00' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (372 commits) mm: swap: check for stable address space before operating on the VMA mm: convert folio_page() back to a macro mm/khugepaged: use start_addr/addr for improved readability hugetlbfs: skip VMAs without shareable locks in hugetlb_vmdelete_list alloc_tag: fix boot failure due to NULL pointer dereference mm: silence data-race in update_hiwater_rss mm/memory-failure: don't select MEMORY_ISOLATION mm/khugepaged: remove definition of struct khugepaged_mm_slot mm/ksm: get mm_slot by mm_slot_entry() when slot is !NULL hugetlb: increase number of reserving hugepages via cmdline selftests/mm: add fork inheritance test for ksm_merging_pages counter mm/ksm: fix incorrect KSM counter handling in mm_struct during fork drivers/base/node: fix double free in register_one_node() mm: remove PMD alignment constraint in execmem_vmalloc() mm/memory_hotplug: fix typo 'esecially' -> 'especially' mm/rmap: improve mlock tracking for large folios mm/filemap: map entire large folio faultaround mm/fault: try to map the entire file folio in finish_fault() mm/rmap: mlock large folios in try_to_unmap_one() mm/rmap: fix a mlock race condition in folio_referenced_one() ...

fs: replace use of system_wq with system_percpu_wq

2025-09-19T14:15:07+00:00

Currently if a user enqueue a work item using schedule_delayed_work() the used wq is "system_wq" (per-cpu wq) while queue_delayed_work() use WORK_CPU_UNBOUND (used when a cpu is not specified). The same applies to schedule_work() that is using system_wq and queue_work(), that makes use again of WORK_CPU_UNBOUND. This lack of consistentcy cannot be addressed without refactoring the API. system_wq is a per-CPU worqueue, yet nothing in its name tells about that CPU affinity constraint, which is very often not required by users. Make it clear by adding a system_percpu_wq to all the fs subsystem. The old wq will be kept for a few release cylces. Suggested-by: Tejun Heo Signed-off-by: Marco Crivellari Link: https://lore.kernel.org/20250916082906.77439-3-marco.crivellari@suse.com Signed-off-by: Christian Brauner