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BUG: KASAN: use-after-free in memcpy_from_page lib/iov_iter.c:472 [inline]
BUG: KASAN: use-after-free in iov_iter_copy_from_user_atomic+0x6a2/0xdb0 lib/iov_iter.c:1005
Read of size 4096 at addr ffff888014495000 by task loop0/28508

CPU: 1 PID: 28508 Comm: loop0 Not tainted 5.10.0-rc1-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+0x137/0x1be lib/dump_stack.c:118
 print_address_description+0x6c/0x660 mm/kasan/report.c:385
 __kasan_report mm/kasan/report.c:545 [inline]
 kasan_report+0x136/0x1e0 mm/kasan/report.c:562
 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:472 [inline]
 iov_iter_copy_from_user_atomic+0x6a2/0xdb0 lib/iov_iter.c:1005
 generic_perform_write+0x2ba/0x4e0 mm/filemap.c:3319
 __generic_file_write_iter+0x222/0x4d0 mm/filemap.c:3440
 generic_file_write_iter+0xa7/0x1b0 mm/filemap.c:3472
 do_iter_readv_writev+0x48c/0x650 include/linux/fs.h:1881
 do_iter_write+0x162/0x5f0 fs/read_write.c:866
 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+0x1e75/0x23c0 drivers/block/loop.c:2066
 kthread_worker_fn+0x42a/0x6f0 kernel/kthread.c:708
 kthread+0x36b/0x390 kernel/kthread.c:292
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:296

The buggy address belongs to the page:
page:0000000012725062 refcount:0 mapcount:-128 mapping:0000000000000000 index:0x0 pfn:0x14495
flags: 0xfff00000000000()
raw: 00fff00000000000 ffffea00004699c8 ffffea00009bfbc8 0000000000000000
raw: 0000000000000000 0000000000000000 00000000ffffff7f 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff888014494f00: fa fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
 ffff888014494f80: fa fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
>ffff888014495000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                   ^
 ffff888014495080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff888014495100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
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