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BUG: KASAN: use-after-free in copy_page_from_iter_atomic+0xab2/0x1540 lib/iov_iter.c:978
Read of size 4096 at addr ffff88802153f000 by task kworker/u4:3/155

CPU: 1 PID: 155 Comm: kworker/u4:3 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
Workqueue: loop1 loop_workfn
Call Trace:
 <TASK>
 dump_stack_lvl+0x188/0x250 lib/dump_stack.c:106
 print_address_description+0x60/0x2d0 mm/kasan/report.c:248
 __kasan_report mm/kasan/report.c:434 [inline]
 kasan_report+0xdf/0x130 mm/kasan/report.c:451
 check_region_inline mm/kasan/generic.c:-1 [inline]
 kasan_check_range+0x235/0x290 mm/kasan/generic.c:189
 memcpy+0x25/0x60 mm/kasan/shadow.c:65
 copy_page_from_iter_atomic+0xab2/0x1540 lib/iov_iter.c:978
 generic_perform_write+0x30b/0x550 mm/filemap.c:3793
 __generic_file_write_iter+0x25f/0x4e0 mm/filemap.c:3912
 generic_file_write_iter+0xa6/0x1b0 mm/filemap.c:3944
 do_iter_readv_writev+0x47e/0x5f0 fs/read_write.c:-1
 do_iter_write+0x205/0x7b0 fs/read_write.c:855
 lo_write_bvec+0x2a6/0x780 drivers/block/loop.c:316
 lo_write_simple drivers/block/loop.c:338 [inline]
 do_req_filebacked drivers/block/loop.c:656 [inline]
 loop_handle_cmd drivers/block/loop.c:2235 [inline]
 loop_process_work+0x1b46/0x24a0 drivers/block/loop.c:2275
 process_one_work+0x85f/0x1010 kernel/workqueue.c:2310
 worker_thread+0xaa6/0x1290 kernel/workqueue.c:2457
 kthread+0x436/0x520 kernel/kthread.c:334
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
 </TASK>

The buggy address belongs to the page:
page:ffffea0000854fc0 refcount:1 mapcount:-512 mapping:0000000000000000 index:0x0 pfn:0x2153f
memcg:ffff888024c53102
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000000000 0000000000000000 0000000000000000 0000000000000000
raw: 0000000000000000 ffff88807757c6c0 00000001fffffdff ffff888024c53102
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 0, migratetype Unmovable, gfp_mask 0x500dc0(GFP_USER|__GFP_ZERO|__GFP_ACCOUNT), pid 5855, ts 124865240194, free_ts 124626451997
 prep_new_page mm/page_alloc.c:2426 [inline]
 get_page_from_freelist+0x1bbd/0x1ca0 mm/page_alloc.c:4192
 __alloc_pages+0x1ee/0x480 mm/page_alloc.c:5501
 pmd_alloc_one include/asm-generic/pgalloc.h:126 [inline]
 __pmd_alloc+0xa6/0x750 mm/memory.c:4958
 pmd_alloc include/linux/mm.h:2191 [inline]
 __handle_mm_fault mm/memory.c:4747 [inline]
 handle_mm_fault+0xbd1/0x4410 mm/memory.c:4883
 do_user_addr_fault+0x489/0xc80 arch/x86/mm/fault.c:1355
 handle_page_fault arch/x86/mm/fault.c:1443 [inline]
 exc_page_fault+0x60/0x100 arch/x86/mm/fault.c:1496
 asm_exc_page_fault+0x22/0x30 arch/x86/include/asm/idtentry.h:606
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:24 [inline]
 free_pages_prepare mm/page_alloc.c:1340 [inline]
 free_pcp_prepare mm/page_alloc.c:1391 [inline]
 free_unref_page_prepare+0x637/0x6c0 mm/page_alloc.c:3317
 free_unref_page+0x8f/0x2a0 mm/page_alloc.c:3396
 lbmLogShutdown fs/jfs/jfs_logmgr.c:1872 [inline]
 lmLogShutdown+0x44b/0x850 fs/jfs/jfs_logmgr.c:1692
 lmLogClose+0x286/0x520 fs/jfs/jfs_logmgr.c:1468
 jfs_umount+0x28f/0x360 fs/jfs/jfs_umount.c:116
 jfs_put_super+0x88/0x190 fs/jfs/super.c:194
 generic_shutdown_super+0x130/0x300 fs/super.c:475
 kill_block_super+0x7c/0xe0 fs/super.c:1427
 deactivate_locked_super+0x93/0xf0 fs/super.c:335
 cleanup_mnt+0x42d/0x4e0 fs/namespace.c:1148
 task_work_run+0x125/0x1a0 kernel/task_work.c:188
 tracehook_notify_resume include/linux/tracehook.h:189 [inline]
 exit_to_user_mode_loop+0x10f/0x130 kernel/entry/common.c:181
 exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:214
 __syscall_exit_to_user_mode_work kernel/entry/common.c:296 [inline]
 syscall_exit_to_user_mode+0x16/0x40 kernel/entry/common.c:307
 do_syscall_64+0x58/0xa0 arch/x86/entry/common.c:86
 entry_SYSCALL_64_after_hwframe+0x66/0xd0

Memory state around the buggy address:
 ffff88802153ef00: fb fb fb fb fb fb fc fc fc fc fa fb fb fb fb fb
 ffff88802153ef80: fb fb fb fb fc fc fc fc fc fc fc fc fc fc fc fc
>ffff88802153f000: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
                   ^
 ffff88802153f080: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff88802153f100: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
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