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Breno Leitao 1bd36e93b5 mm: blk-cgroup: fix use-after-free in cgwb_release_workfn() 
[ Upstream commit 8f5857be99 ]

cgwb_release_workfn() calls css_put(wb->blkcg_css) and then later accesses
wb->blkcg_css again via blkcg_unpin_online().  If css_put() drops the last
reference, the blkcg can be freed asynchronously (css_free_rwork_fn ->
blkcg_css_free -> kfree) before blkcg_unpin_online() dereferences the
pointer to access blkcg->online_pin, resulting in a use-after-free:

  BUG: KASAN: slab-use-after-free in blkcg_unpin_online (./include/linux/instrumented.h:112 ./include/linux/atomic/atomic-instrumented.h:400 ./include/linux/refcount.h:389 ./include/linux/refcount.h:432 ./include/linux/refcount.h:450 block/blk-cgroup.c:1367)
  Write of size 4 at addr ff11000117aa6160 by task kworker/71:1/531
   Workqueue: cgwb_release cgwb_release_workfn
   Call Trace:
    <TASK>
     blkcg_unpin_online (./include/linux/instrumented.h:112 ./include/linux/atomic/atomic-instrumented.h:400 ./include/linux/refcount.h:389 ./include/linux/refcount.h:432 ./include/linux/refcount.h:450 block/blk-cgroup.c:1367)
     cgwb_release_workfn (mm/backing-dev.c:629)
     process_scheduled_works (kernel/workqueue.c:3278 kernel/workqueue.c:3385)

   Freed by task 1016:
    kfree (./include/linux/kasan.h:235 mm/slub.c:2689 mm/slub.c:6246 mm/slub.c:6561)
    css_free_rwork_fn (kernel/cgroup/cgroup.c:5542)
    process_scheduled_works (kernel/workqueue.c:3302 kernel/workqueue.c:3385)

** Stack based on commit 66672af7a095 ("Add linux-next specific files
for 20260410")

I am seeing this crash sporadically in Meta fleet across multiple kernel
versions.  A full reproducer is available at:
https://github.com/leitao/debug/blob/main/reproducers/repro_blkcg_uaf.sh

(The race window is narrow.  To make it easily reproducible, inject a
msleep(100) between css_put() and blkcg_unpin_online() in
cgwb_release_workfn().  With that delay and a KASAN-enabled kernel, the
reproducer triggers the splat reliably in less than a second.)

Fix this by moving blkcg_unpin_online() before css_put(), so the
cgwb's CSS reference keeps the blkcg alive while blkcg_unpin_online()
accesses it.

Link: https://lore.kernel.org/20260413-blkcg-v1-1-35b72622d16c@debian.org
Fixes: 59b57717ff ("blkcg: delay blkg destruction until after writeback has finished")
Signed-off-by: Breno Leitao <leitao@debian.org>
Reviewed-by: Dennis Zhou <dennis@kernel.org>
Reviewed-by: Shakeel Butt <shakeel.butt@linux.dev>
Cc: David Hildenbrand <david@kernel.org>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Josef Bacik <josef@toxicpanda.com>
Cc: JP Kobryn <inwardvessel@gmail.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Lorenzo Stoakes (Oracle) <ljs@kernel.org>
Cc: Martin KaFai Lau <martin.lau@linux.dev>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
History 2026-06-01 17:35:08 +02:00
..
damon mm/damon/tests/core-kunit: handle memory alloc failure from damon_test_aggregate() 2026-01-19 13:10:05 +01:00
kasan mm/kasan: fix double free for kasan pXds 2026-06-01 17:35:06 +02:00
kfence mm/kfence: randomize the freelist on initialization 2026-02-11 13:35:27 +01:00
backing-dev.c mm: blk-cgroup: fix use-after-free in cgwb_release_workfn() 2026-06-01 17:35:08 +02:00
balloon_compaction.c mm/balloon_compaction: convert balloon_page_delete() to balloon_page_finalize() 2026-01-19 13:10:10 +01:00
bootmem_info.c bootmem: remove the vmemmap pages from kmemleak in put_page_bootmem 2022-08-31 17:16:48 +02:00
cleancache.c Driver Core and debugfs changes for 5.3-rc1 2019-07-12 12:24:03 -07:00
cma.c mm/cma: drop incorrect alignment check in cma_init_reserved_mem 2024-07-05 09:14:13 +02:00
cma.h mm: cma: support sysfs 2021-05-05 11:27:24 -07:00
cma_debug.c mm/cma: change cma mutex to irq safe spinlock 2021-05-05 11:27:21 -07:00
cma_sysfs.c mm: cma: support sysfs 2021-05-05 11:27:24 -07:00
compaction.c mm, vmscan: prevent infinite loop for costly GFP_NOIO | __GFP_RETRY_MAYFAIL allocations 2024-04-10 16:19:37 +02:00
debug.c mm/debug: sync up latest migrate_reason to migrate_reason_names 2021-09-24 16:13:35 -07:00
debug_page_ref.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
debug_vm_pgtable.c mm/debug_vm_pgtable: clear page table entries at destroy_args() 2025-08-28 16:24:34 +02:00
dmapool.c mm/dmapool: use DEVICE_ATTR_RO macro 2021-06-29 10:53:52 -07:00
early_ioremap.c mm/early_ioremap.c: remove redundant early_ioremap_shutdown() 2021-09-08 11:50:24 -07:00
fadvise.c mm, fadvise: improve the expensive remote LRU cache draining after FADV_DONTNEED 2020-10-13 18:38:29 -07:00
failslab.c mm/failslab.c: by default, do not fail allocations with direct reclaim only 2019-07-12 11:05:43 -07:00
filemap.c mm: drop the assumption that VM_SHARED always implies writable 2025-08-28 16:24:30 +02:00
frontswap.c mm/mempool: minor coding style tweaks 2021-05-05 11:27:27 -07:00
gup.c mm/gup: fix wrongly calculated returned value in fault_in_safe_writeable() 2025-05-02 07:44:13 +02:00
gup_test.c selftests/vm: gup_test: test faulting in kernel, and verify pinnable pages 2021-05-05 11:27:26 -07:00
gup_test.h selftests/vm: gup_test: fix test flag 2021-05-05 11:27:26 -07:00
highmem.c highmem: fix checks in __kmap_local_sched_{in,out} 2022-04-13 20:59:21 +02:00
hmm.c mm/hmm: move pmd_to_hmm_pfn_flags() to the respective #ifdeffery 2025-08-28 16:24:14 +02:00
huge_memory.c mm/huge_memory: fix dereferencing invalid pmd migration entry 2025-06-27 11:05:37 +01:00
hugetlb.c mm/hugetlb: fix excessive IPI broadcasts when unsharing PMD tables using mmu_gather 2026-04-18 10:33:18 +02:00
hugetlb_cgroup.c hugetlb: make free_huge_page irq safe 2021-05-05 11:27:22 -07:00
hugetlb_vmemmap.c mm: hugetlb: introduce CONFIG_HUGETLB_PAGE_FREE_VMEMMAP_DEFAULT_ON 2021-06-30 20:47:26 -07:00
hugetlb_vmemmap.h mm: hugetlb: introduce nr_free_vmemmap_pages in the struct hstate 2021-06-30 20:47:25 -07:00
hwpoison-inject.c mm/hwpoison: avoid the impact of hwpoison_filter() return value on mce handler 2022-07-12 16:35:05 +02:00
init-mm.c mm: add setup_initial_init_mm() helper 2021-07-08 11:48:21 -07:00
internal.h mm: unconditionally close VMAs on error 2024-12-14 19:50:38 +01:00
interval_tree.c mm/interval_tree: add comments to improve code readability 2021-04-30 11:20:38 -07:00
io-mapping.c mm: add a io_mapping_map_user helper 2021-04-30 11:20:39 -07:00
ioremap.c mm: move ioremap_page_range to vmalloc.c 2021-09-08 11:50:24 -07:00
Kconfig x86/kaslr: Recognize all ZONE_DEVICE users as physaddr consumers 2026-02-06 16:41:47 +01:00
Kconfig.debug mm, page_poison: remove CONFIG_PAGE_POISONING_ZERO 2020-12-15 12:13:46 -08:00
khugepaged.c mm/khugepaged: fix the address passed to notifier on testing young 2025-10-02 13:39:01 +02:00
kmemleak.c mm/kmemleak: avoid deadlock by moving pr_warn() outside kmemleak_lock 2025-08-28 16:24:27 +02:00
ksm.c ksm: use range-walk function to jump over holes in scan_get_next_rmap_item 2026-02-06 16:42:03 +01:00
list_lru.c mm: vmscan: consolidate shrinker_maps handling code 2021-05-05 11:27:23 -07:00
maccess.c maccess: Fix writing offset in case of fault in strncpy_from_kernel_nofault() 2022-11-26 09:24:47 +01:00
madvise.c mm: drop the assumption that VM_SHARED always implies writable 2025-08-28 16:24:30 +02:00
Makefile mm: introduce Data Access MONitor (DAMON) 2021-09-08 11:50:24 -07:00
mapping_dirty_helpers.c mm/mapping_dirty_helpers: remove double Note in kerneldoc 2021-07-01 11:06:02 -07:00
memblock.c memblock: allow to specify flags with memblock_add_node() 2023-12-20 15:17:33 +01:00
memcontrol.c memcg: always call cond_resched() after fn() 2025-06-04 14:38:06 +02:00
memfd.c mm: reinstate ability to map write-sealed memfd mappings read-only 2025-08-28 16:24:30 +02:00
memory-failure.c mm/memory-failure: fix VM_BUG_ON_PAGE(PagePoisoned(page)) when unpoison memory 2025-10-02 13:39:05 +02:00
memory.c mm: fix apply_to_existing_page_range() 2025-05-02 07:44:24 +02:00
memory_hotplug.c memblock: allow to specify flags with memblock_add_node() 2023-12-20 15:17:33 +01:00
mempolicy.c mm/numa_balancing: teach mpol_to_str about the balancing mode 2024-08-19 05:45:17 +02:00
mempool.c kasan: use separate (un)poison implementation for integrated init 2021-06-04 19:32:21 +01:00
memremap.c mm/memremap.c: map FS_DAX device memory as decrypted 2022-11-16 09:58:27 +01:00
memtest.c memtest: use {READ,WRITE}_ONCE in memory scanning 2024-04-10 16:18:42 +02:00
migrate.c migrate: correct lock ordering for hugetlb file folios 2026-02-06 16:41:58 +01:00
mincore.c inode: make init and permission helpers idmapped mount aware 2021-01-24 14:27:16 +01:00
mlock.c mm/mlock: fix potential imbalanced rlimit ucounts adjustment 2022-05-15 20:18:53 +02:00
mm_init.c include/linux/page-flags-layout.h: cleanups 2021-04-30 11:20:42 -07:00
mmap.c mm: reinstate ability to map write-sealed memfd mappings read-only 2025-08-28 16:24:30 +02:00
mmap_lock.c mm: mmap_lock: replace get_memcg_path_buf() with on-stack buffer 2024-08-19 05:45:10 +02:00
mmu_gather.c mm/hugetlb: fix excessive IPI broadcasts when unsharing PMD tables using mmu_gather 2026-04-18 10:33:18 +02:00
mmu_notifier.c mm/mmu_notifier.c: fix race in mmu_interval_notifier_remove() 2022-04-27 14:38:58 +02:00
mmzone.c mm/lru: replace pgdat lru_lock with lruvec lock 2020-12-15 14:48:04 -08:00
mprotect.c mm: don't try to NUMA-migrate COW pages that have other uses 2022-02-23 12:03:03 +01:00
mremap.c mmmremap.c: avoid pointless invalidate_range_start/end on mremap(old_size=0) 2022-04-13 20:59:22 +02:00
msync.c mm/msync: exit early when the flags is an MS_ASYNC and start < vm_start 2021-04-30 11:20:37 -07:00
nommu.c mm: refactor arch_calc_vm_flag_bits() and arm64 MTE handling 2024-12-14 19:50:38 +01:00
oom_kill.c memcg: fix soft lockup in the OOM process 2025-03-13 12:50:48 +01:00
page-writeback.c mm: fix ratelimit_pages update error in dirty_ratio_handler() 2025-06-27 11:05:26 +01:00
page_alloc.c mm, page_alloc, thp: prevent reclaim for __GFP_THISNODE THP allocations 2026-03-04 07:20:30 -05:00
page_counter.c mm: page_counter: mitigate consequences of a page_counter underflow 2021-04-30 11:20:38 -07:00
page_ext.c mm/migrate: add CPU hotplug to demotion #ifdef 2021-10-18 20:22:02 -10:00
page_idle.c mm/idle_page_tracking: make PG_idle reusable 2021-09-08 11:50:24 -07:00
page_io.c mm: fix unexpected zeroed page mapping with zram swap 2022-04-20 09:34:18 +02:00
page_isolation.c Merge branch 'akpm' (patches from Andrew) 2021-09-08 12:55:35 -07:00
page_owner.c mm: remove pfn_valid_within() and CONFIG_HOLES_IN_ZONE 2021-09-08 11:50:22 -07:00
page_poison.c mm: page_poison: print page info when corruption is caught 2021-04-30 11:20:36 -07:00
page_reporting.c mm/page_reporting: allow driver to specify reporting order 2021-06-29 10:53:47 -07:00
page_reporting.h mm/page_reporting: export reporting order as module parameter 2021-06-29 10:53:47 -07:00
page_vma_mapped.c mm: device exclusive memory access 2021-07-01 11:06:03 -07:00
pagewalk.c mm/pagewalk: add walk_page_range_vma() 2026-02-06 16:42:03 +01:00
percpu-internal.h Merge branch 'for-5.14' of git://git.kernel.org/pub/scm/linux/kernel/git/dennis/percpu 2021-07-01 17:17:24 -07:00
percpu-km.c percpu: flush tlb in pcpu_reclaim_populated() 2021-07-04 18:30:17 +00:00
percpu-stats.c percpu: rework memcg accounting 2021-06-05 20:43:15 +00:00
percpu-vm.c percpu: flush tlb in pcpu_reclaim_populated() 2021-07-04 18:30:17 +00:00
percpu.c memblock: drop memblock_free_early_nid() and memblock_free_early() 2025-03-13 12:50:07 +01:00
pgalloc-track.h mm: fix typos in comments 2021-05-07 00:26:35 -07:00
pgtable-generic.c mm/thp: fix __split_huge_pmd_locked() on shmem migration entry 2021-06-16 09:24:42 -07:00
process_vm_access.c mm/process_vm_access.c: remove duplicate include 2021-05-05 11:27:27 -07:00
ptdump.c mm/ptdump: take the memory hotplug lock inside ptdump_walk_pgd() 2025-08-28 16:24:32 +02:00
readahead.c vfs: fix readahead(2) on block devices 2023-11-20 11:08:13 +01:00
rmap.c mm/hugetlb: fix excessive IPI broadcasts when unsharing PMD tables using mmu_gather 2026-04-18 10:33:18 +02:00
rodata_test.c mm/rodata_test.c: fix missing function declaration 2020-08-21 09:52:53 -07:00
secretmem.c mm/secretmem: fix use-after-free race in fault handler 2025-12-07 06:09:32 +09:00
shmem.c mm: update memfd seal write check to include F_SEAL_WRITE 2025-08-28 16:24:30 +02:00
shuffle.c mm: eliminate "expecting prototype" kernel-doc warnings 2021-04-16 16:10:36 -07:00
shuffle.h mm/shuffle: fix section mismatch warning 2021-05-22 15:09:07 -10:00
slab.c slab: Introduce kmalloc_size_roundup() 2025-04-10 14:31:49 +02:00
slab.h mm, kfence: support kmem_dump_obj() for KFENCE objects 2022-04-27 14:38:51 +02:00
slab_common.c mm, slab: remove duplicate kernel-doc comment for ksize() 2025-04-10 14:32:06 +02:00
slob.c slab: Introduce kmalloc_size_roundup() 2025-04-10 14:31:49 +02:00
slub.c mm/slub: avoid accessing metadata when pointer is invalid in object_err() 2025-09-09 18:50:24 +02:00
sparse-vmemmap.c mm: introduce and use {pgd,p4d}_populate_kernel() 2025-10-02 13:38:59 +02:00
sparse.c memblock: drop memblock_free_early_nid() and memblock_free_early() 2025-03-13 12:50:07 +01:00
swap.c mm: fs: invalidate bh_lrus for only cold path 2021-09-24 16:13:35 -07:00
swap_cgroup.c mm: memcontrol: make swap tracking an integral part of memory control 2020-06-03 20:09:48 -07:00
swap_slots.c mm: Replace deprecated CPU-hotplug functions. 2021-08-28 01:46:17 +02:00
swap_state.c mm: swap: get rid of livelock in swapin readahead 2022-03-23 09:16:41 +01:00
swapfile.c mm/swapfile: skip HugeTLB pages for unuse_vma 2024-10-22 15:40:41 +02:00
truncate.c Merge branch 'akpm' (patches from Andrew) 2021-09-03 10:08:28 -07:00
usercopy.c mm/usercopy: return 1 from hardened_usercopy __setup() handler 2022-04-08 14:24:14 +02:00
userfaultfd.c userfaultfd: fix mmap_changing checking in mfill_atomic_hugetlb 2024-03-01 13:21:43 +01:00
util.c mm: unconditionally close VMAs on error 2024-12-14 19:50:38 +01:00
vmacache.c kernel: better document the use_mm/unuse_mm API contract 2020-06-10 19:14:18 -07:00
vmalloc.c mm/vmalloc: leave lazy MMU mode on PTE mapping error 2025-08-28 16:24:03 +02:00
vmpressure.c net-memcg: Fix scope of sockmem pressure indicators 2023-09-19 12:22:33 +02:00
vmscan.c mm: add missing release barrier on PGDAT_RECLAIM_LOCKED unlock 2025-05-02 07:44:04 +02:00
vmstat.c vmstat: call fold_vm_zone_numa_events() before show per zone NUMA event 2024-12-14 19:50:33 +01:00
workingset.c memcg: sync flush only if periodic flush is delayed 2022-04-27 14:38:57 +02:00
z3fold.c mm/z3fold: add kerneldoc fields for z3fold_pool 2021-07-01 11:06:03 -07:00
zbud.c mm/zbud: add kerneldoc fields for zbud_pool 2021-07-01 11:06:03 -07:00
zpool.c mm: fix typos in comments 2021-05-07 00:26:35 -07:00
zsmalloc.c minmax: make generic MIN() and MAX() macros available everywhere 2025-10-19 16:21:52 +02:00
zswap.c mm/zswap.c: fix two bugs in zswap_writeback_entry() 2021-06-30 20:47:31 -07:00