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BUG: KMSAN: uninit-value in lo_write_simple drivers/block/loop.c:293 [inline]
BUG: KMSAN: uninit-value in do_req_filebacked drivers/block/loop.c:604 [inline]
BUG: KMSAN: uninit-value in loop_handle_cmd drivers/block/loop.c:1772 [inline]
BUG: KMSAN: uninit-value in loop_queue_work+0x350f/0x3d30 drivers/block/loop.c:1786
CPU: 0 PID: 10634 Comm: loop7 Not tainted 4.17.0-rc5+ #103
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+0x185/0x1d0 lib/dump_stack.c:113
 kmsan_report+0x149/0x260 mm/kmsan/kmsan.c:1084
 __msan_warning_32+0x6e/0xc0 mm/kmsan/kmsan_instr.c:686
 lo_write_simple drivers/block/loop.c:293 [inline]
 do_req_filebacked drivers/block/loop.c:604 [inline]
 loop_handle_cmd drivers/block/loop.c:1772 [inline]
 loop_queue_work+0x350f/0x3d30 drivers/block/loop.c:1786
 kthread_worker_fn+0x58f/0x900 kernel/kthread.c:640
 loop_kthread_worker_fn+0x90/0xb0 drivers/block/loop.c:863
 kthread+0x4e3/0x6d0 kernel/kthread.c:241
 ret_from_fork+0x35/0x40 arch/x86/entry/entry_64.S:412

Uninit was stored to memory at:
 kmsan_save_stack_with_flags mm/kmsan/kmsan.c:279 [inline]
 kmsan_save_stack mm/kmsan/kmsan.c:294 [inline]
 kmsan_internal_chain_origin+0x12b/0x210 mm/kmsan/kmsan.c:685
 __msan_chain_origin+0x69/0xc0 mm/kmsan/kmsan_instr.c:529
 blk_rq_bio_prep block/blk-core.c:3409 [inline]
 blk_init_request_from_bio+0x81b/0x8d0 block/blk-core.c:1994
 blk_mq_bio_to_request+0x72/0x550 block/blk-mq.c:1712
 blk_mq_make_request+0xccf/0x24b0 block/blk-mq.c:1901
 generic_make_request+0x73d/0x18f0 block/blk-core.c:2460
 submit_bio+0x2e8/0x740 block/blk-core.c:2568
 submit_bh_wbc+0xb3b/0xe00 fs/buffer.c:3081
 __block_write_full_page+0x12ea/0x1e10 fs/buffer.c:1763
 block_write_full_page+0x32c/0x440 fs/buffer.c:2949
 blkdev_writepage+0x76/0x90 fs/block_dev.c:566
 __writepage+0xc0/0x200 mm/page-writeback.c:2302
 write_cache_pages+0x124e/0x1800 mm/page-writeback.c:2240
 generic_writepages+0x10f/0x190 mm/page-writeback.c:2326
 blkdev_writepages+0x67/0x80 fs/block_dev.c:1951
 do_writepages+0x185/0x3c0 mm/page-writeback.c:2341
 __filemap_fdatawrite_range+0x4b6/0x500 mm/filemap.c:445
 __filemap_fdatawrite mm/filemap.c:453 [inline]
 filemap_fdatawrite mm/filemap.c:458 [inline]
 filemap_write_and_wait+0x25e/0x950 mm/filemap.c:617
 __sync_blockdev fs/block_dev.c:448 [inline]
 sync_blockdev fs/block_dev.c:457 [inline]
 __blkdev_put+0x2ba/0xc80 fs/block_dev.c:1783
 blkdev_put+0x435/0x570 fs/block_dev.c:1852
 blkdev_close+0xa6/0xf0 fs/block_dev.c:1859
 __fput+0x457/0xa10 fs/file_table.c:209
 ____fput+0x37/0x40 fs/file_table.c:243
 task_work_run+0x243/0x2c0 kernel/task_work.c:113
 exit_task_work include/linux/task_work.h:22 [inline]
 do_exit+0x10e1/0x38d0 kernel/exit.c:867
 do_group_exit+0x1a0/0x360 kernel/exit.c:970
 get_signal+0xfcb/0x1f40 kernel/signal.c:2482
 do_signal+0xb8/0x1cf0 arch/x86/kernel/signal.c:810
 exit_to_usermode_loop arch/x86/entry/common.c:162 [inline]
 prepare_exit_to_usermode+0x271/0x3a0 arch/x86/entry/common.c:196
 syscall_return_slowpath+0xe9/0x700 arch/x86/entry/common.c:265
 do_syscall_64+0x1af/0x230 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
Local variable description: ----bio.addr@blk_mq_make_request
Variable was created at:
 blk_mq_make_request+0xb2/0x24b0 block/blk-mq.c:1848
 generic_make_request+0x73d/0x18f0 block/blk-core.c:2460
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