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BUG: KASAN: use-after-free in memcpy_from_page lib/iov_iter.c:467 [inline]
BUG: KASAN: use-after-free in iov_iter_copy_from_user_atomic+0x860/0xd90 lib/iov_iter.c:1000
Read of size 4096 at addr ffff8880a1480000 by task loop0/28322

CPU: 1 PID: 28322 Comm: loop0 Not tainted 5.9.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x1d6/0x29e lib/dump_stack.c:118
 print_address_description+0x66/0x620 mm/kasan/report.c:383
 __kasan_report mm/kasan/report.c:513 [inline]
 kasan_report+0x132/0x1d0 mm/kasan/report.c:530
 check_memory_region_inline mm/kasan/generic.c:183 [inline]
 check_memory_region+0x2b5/0x2f0 mm/kasan/generic.c:192
 memcpy+0x25/0x60 mm/kasan/common.c:105
 memcpy_from_page lib/iov_iter.c:467 [inline]
 iov_iter_copy_from_user_atomic+0x860/0xd90 lib/iov_iter.c:1000
 generic_perform_write+0x2ba/0x4e0 mm/filemap.c:3513
 __generic_file_write_iter+0x22b/0x4e0 mm/filemap.c:3634
 generic_file_write_iter+0x4a6/0x650 mm/filemap.c:3666
 do_iter_readv_writev+0x4f9/0x6c0 include/linux/fs.h:1868
 do_iter_write+0x164/0x610 fs/read_write.c:847
 lo_write_bvec+0x11e/0x330 drivers/block/loop.c:287
 lo_write_simple drivers/block/loop.c:309 [inline]
 do_req_filebacked drivers/block/loop.c:632 [inline]
 loop_handle_cmd drivers/block/loop.c:2048 [inline]
 loop_queue_work+0x1ddd/0x2330 drivers/block/loop.c:2066
 kthread_worker_fn+0x42a/0x6f0 kernel/kthread.c:708
 kthread+0x37e/0x3a0 drivers/block/aoe/aoecmd.c:1234
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294

The buggy address belongs to the page:
page:00000000e808769b refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0xa1480
flags: 0xfffe0000000000()
raw: 00fffe0000000000 ffffea000238e188 ffffea00029f6948 0000000000000000
raw: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8880a147ff00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8880a147ff80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff8880a1480000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                   ^
 ffff8880a1480080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff8880a1480100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
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