==================================================================
BUG: KMSAN: uninit-value in copyout lib/iov_iter.c:140 [inline]
BUG: KMSAN: uninit-value in copy_page_to_iter_iovec lib/iov_iter.c:212 [inline]
BUG: KMSAN: uninit-value in copy_page_to_iter+0x754/0x1b70 lib/iov_iter.c:716
CPU: 1 PID: 7261 Comm: blkid Not tainted 4.16.0+ #84
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:17 [inline]
 dump_stack+0x185/0x1d0 lib/dump_stack.c:53
 kmsan_report+0x142/0x240 mm/kmsan/kmsan.c:1067
 kmsan_internal_check_memory+0x174/0x1e0 mm/kmsan/kmsan.c:1176
 kmsan_copy_to_user+0x69/0x160 mm/kmsan/kmsan.c:1199
 copyout lib/iov_iter.c:140 [inline]
 copy_page_to_iter_iovec lib/iov_iter.c:212 [inline]
 copy_page_to_iter+0x754/0x1b70 lib/iov_iter.c:716
 generic_file_buffered_read mm/filemap.c:2187 [inline]
 generic_file_read_iter+0x2ee8/0x43f0 mm/filemap.c:2364
 blkdev_read_iter+0x20d/0x280 fs/block_dev.c:1928
 call_read_iter include/linux/fs.h:1776 [inline]
 new_sync_read fs/read_write.c:401 [inline]
 __vfs_read+0x6fb/0x8e0 fs/read_write.c:413
 vfs_read+0x36c/0x6c0 fs/read_write.c:447
 SYSC_read+0x172/0x360 fs/read_write.c:573
 SyS_read+0x55/0x80 fs/read_write.c:566
 do_syscall_64+0x309/0x430 arch/x86/entry/common.c:287
 entry_SYSCALL_64_after_hwframe+0x3d/0xa2
RIP: 0033:0x7f4622427310
RSP: 002b:00007ffc3cb3d668 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f4622427310
RDX: 0000000000000400 RSI: 0000000000e35c58 RDI: 0000000000000003
RBP: 0000000000e35c30 R08: 0000000000000028 R09: 0000000001680000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000e35030
R13: 0000000000000400 R14: 0000000000e35080 R15: 0000000000e35c48

Uninit was stored to memory at:
 kmsan_save_stack_with_flags mm/kmsan/kmsan.c:278 [inline]
 kmsan_save_stack mm/kmsan/kmsan.c:293 [inline]
 kmsan_internal_chain_origin+0x12b/0x210 mm/kmsan/kmsan.c:684
 kmsan_memcpy_origins+0x11d/0x170 mm/kmsan/kmsan.c:526
 __msan_memcpy+0x19f/0x1f0 mm/kmsan/kmsan_instr.c:470
 memcpy_to_page lib/iov_iter.c:466 [inline]
 _copy_to_iter+0x852/0x28f0 lib/iov_iter.c:571
 copy_to_iter include/linux/uio.h:106 [inline]
 copy_page_to_iter+0x383/0x1b70 lib/iov_iter.c:712
 shmem_file_read_iter+0x99f/0x1180 mm/shmem.c:2507
 do_iter_readv_writev+0x7bb/0x970 include/linux/fs.h:1776
 do_iter_read+0x303/0xd70 fs/read_write.c:895
 vfs_iter_read+0x118/0x180 fs/read_write.c:909
 lo_read_simple drivers/block/loop.c:348 [inline]
 do_req_filebacked drivers/block/loop.c:589 [inline]
 loop_handle_cmd drivers/block/loop.c:1724 [inline]
 loop_queue_work+0x270e/0x3ef0 drivers/block/loop.c:1738
 kthread_worker_fn+0x58f/0x900 kernel/kthread.c:644
 loop_kthread_worker_fn+0x90/0xb0 drivers/block/loop.c:841
 kthread+0x539/0x720 kernel/kthread.c:239
 ret_from_fork+0x35/0x40 arch/x86/entry/entry_64.S:406
Uninit was created at:
 kmsan_save_stack_with_flags mm/kmsan/kmsan.c:278 [inline]
 kmsan_alloc_meta_for_pages+0x161/0x3a0 mm/kmsan/kmsan.c:814
 kmsan_alloc_page+0x82/0xe0 mm/kmsan/kmsan.c:868
 __alloc_pages_nodemask+0xf5b/0x5dc0 mm/page_alloc.c:4283
 alloc_pages_vma+0xcc8/0x1800 mm/mempolicy.c:2019
 shmem_alloc_page mm/shmem.c:1471 [inline]
 shmem_alloc_and_acct_page+0x6d5/0x1000 mm/shmem.c:1496
 shmem_getpage_gfp+0x35db/0x5770 mm/shmem.c:1771
 shmem_getpage mm/shmem.c:131 [inline]
 shmem_file_read_iter+0x508/0x1180 mm/shmem.c:2456
 do_iter_readv_writev+0x7bb/0x970 include/linux/fs.h:1776
 do_iter_read+0x303/0xd70 fs/read_write.c:895
 vfs_iter_read+0x118/0x180 fs/read_write.c:909
 lo_read_simple drivers/block/loop.c:348 [inline]
 do_req_filebacked drivers/block/loop.c:589 [inline]
 loop_handle_cmd drivers/block/loop.c:1724 [inline]
 loop_queue_work+0x270e/0x3ef0 drivers/block/loop.c:1738
 kthread_worker_fn+0x58f/0x900 kernel/kthread.c:644
 loop_kthread_worker_fn+0x90/0xb0 drivers/block/loop.c:841
 kthread+0x539/0x720 kernel/kthread.c:239
 ret_from_fork+0x35/0x40 arch/x86/entry/entry_64.S:406

Bytes 4-1023 of 1024 are uninitialized
==================================================================