syzbot

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BUG: KMSAN: uninit-value in do_req_filebacked drivers/block/loop.c:592 [inline]
BUG: KMSAN: uninit-value in loop_handle_cmd drivers/block/loop.c:1773 [inline]
BUG: KMSAN: uninit-value in loop_queue_work+0x1ff0/0x3e30 drivers/block/loop.c:1787
CPU: 0 PID: 21986 Comm: loop0 Not tainted 4.17.0+ #8
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+0x188/0x2a0 mm/kmsan/kmsan.c:1122
 __msan_warning_32+0x70/0xc0 mm/kmsan/kmsan_instr.c:620
 do_req_filebacked drivers/block/loop.c:592 [inline]
 loop_handle_cmd drivers/block/loop.c:1773 [inline]
 loop_queue_work+0x1ff0/0x3e30 drivers/block/loop.c:1787
 kthread_worker_fn+0x595/0x900 kernel/kthread.c:638
 loop_kthread_worker_fn+0x90/0xb0 drivers/block/loop.c:863
 kthread+0x4db/0x6c0 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:686
 __msan_chain_origin+0x69/0xc0 mm/kmsan/kmsan_instr.c:464
 blk_mq_rq_ctx_init block/blk-mq.c:302 [inline]
 blk_mq_get_request+0xee5/0x1b20 block/blk-mq.c:380
 blk_mq_make_request+0x90d/0x2440 block/blk-mq.c:1877
 generic_make_request+0x733/0x18f0 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+0xc5/0x200 mm/page-writeback.c:2302
 write_cache_pages+0x123f/0x1870 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+0x184/0x3c0 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/0xc90 fs/block_dev.c:1783
 blkdev_put+0x435/0x570 fs/block_dev.c:1852
 blkdev_close+0xa6/0xf0 fs/block_dev.c:1859
 __fput+0x458/0xa30 fs/file_table.c:209
 ____fput+0x37/0x40 fs/file_table.c:243
 task_work_run+0x22e/0x2b0 kernel/task_work.c:113
 exit_task_work include/linux/task_work.h:22 [inline]
 do_exit+0x110e/0x3930 kernel/exit.c:867
 do_group_exit+0x1a0/0x360 kernel/exit.c:970
 __do_sys_exit_group+0x21/0x30 kernel/exit.c:981
 __se_sys_exit_group+0x14/0x20 kernel/exit.c:979
 __x64_sys_exit_group+0x4c/0x50 kernel/exit.c:979
 do_syscall_64+0x15b/0x230 arch/x86/entry/common.c:287
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

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:686
 __msan_chain_origin+0x69/0xc0 mm/kmsan/kmsan_instr.c:464
 bio_set_op_attrs include/linux/blk_types.h:325 [inline]
 submit_bh_wbc+0xd57/0xe00 fs/buffer.c:3079
 __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+0xc5/0x200 mm/page-writeback.c:2302
 write_cache_pages+0x123f/0x1870 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+0x184/0x3c0 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/0xc90 fs/block_dev.c:1783
 blkdev_put+0x435/0x570 fs/block_dev.c:1852
 blkdev_close+0xa6/0xf0 fs/block_dev.c:1859
 __fput+0x458/0xa30 fs/file_table.c:209
 ____fput+0x37/0x40 fs/file_table.c:243
 task_work_run+0x22e/0x2b0 kernel/task_work.c:113
 exit_task_work include/linux/task_work.h:22 [inline]
 do_exit+0x110e/0x3930 kernel/exit.c:867
 do_group_exit+0x1a0/0x360 kernel/exit.c:970
 __do_sys_exit_group+0x21/0x30 kernel/exit.c:981
 __se_sys_exit_group+0x14/0x20 kernel/exit.c:979
 __x64_sys_exit_group+0x4c/0x50 kernel/exit.c:979
 do_syscall_64+0x15b/0x230 arch/x86/entry/common.c:287
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Local variable description: ----flags.i.i.i.i@_raw_spin_lock_irqsave
Variable was created at:
 _raw_spin_lock_irqsave+0x45/0xf0 kernel/locking/spinlock.c:150
 hrtimer_interrupt+0x107/0x13c0 kernel/time/hrtimer.c:1499
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