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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: 15695 Comm: blkid 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
 kmsan_internal_check_memory+0x179/0x1e0 mm/kmsan/kmsan.c:1196
 kmsan_copy_to_user+0x75/0x160 mm/kmsan/kmsan.c:1219
 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:2185 [inline]
 generic_file_read_iter+0x2fa5/0x44e0 mm/filemap.c:2362
 blkdev_read_iter+0x20d/0x280 fs/block_dev.c:1930
 call_read_iter include/linux/fs.h:1778 [inline]
 new_sync_read fs/read_write.c:406 [inline]
 __vfs_read+0x7dd/0x9b0 fs/read_write.c:418
 vfs_read+0x36c/0x6b0 fs/read_write.c:452
 ksys_read fs/read_write.c:578 [inline]
 __do_sys_read fs/read_write.c:588 [inline]
 __se_sys_read fs/read_write.c:586 [inline]
 __x64_sys_read+0x1bf/0x3e0 fs/read_write.c:586
 do_syscall_64+0x152/0x230 arch/x86/entry/common.c:287
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x7f150c105310
RSP: 002b:00007ffdde765418 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f150c105310
RDX: 0000000000000400 RSI: 000000000095eb18 RDI: 0000000000000003
RBP: 000000000095eaf0 R08: 0000000000000028 R09: 0000000001680000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000095c030
R13: 0000000000000400 R14: 000000000095c080 R15: 000000000095eb08

Uninit was created at:
 kmsan_save_stack_with_flags mm/kmsan/kmsan.c:279 [inline]
 kmsan_alloc_meta_for_pages+0x161/0x3a0 mm/kmsan/kmsan.c:815
 kmsan_alloc_page+0x82/0xe0 mm/kmsan/kmsan.c:885
 __alloc_pages_nodemask+0xfc0/0x5dc0 mm/page_alloc.c:4402
 alloc_pages_current+0x6b1/0x970 mm/mempolicy.c:2093
 alloc_pages include/linux/gfp.h:494 [inline]
 __page_cache_alloc+0x95/0x320 mm/filemap.c:946
 pagecache_get_page+0x52b/0x1450 mm/filemap.c:1577
 grab_cache_page_write_begin+0x10d/0x190 mm/filemap.c:3089
 block_write_begin+0xf9/0x3a0 fs/buffer.c:2068
 blkdev_write_begin+0xf5/0x110 fs/block_dev.c:584
 generic_perform_write+0x426/0x9a0 mm/filemap.c:3139
 __generic_file_write_iter+0x43b/0xa10 mm/filemap.c:3264
 blkdev_write_iter+0x3a8/0x5f0 fs/block_dev.c:1910
 do_iter_readv_writev+0x84d/0xa00 include/linux/fs.h:1778
 do_iter_write+0x30d/0xd40 fs/read_write.c:959
 vfs_writev fs/read_write.c:1004 [inline]
 do_pwritev+0x480/0x7a0 fs/read_write.c:1093
 __do_sys_pwritev fs/read_write.c:1140 [inline]
 __se_sys_pwritev fs/read_write.c:1135 [inline]
 __x64_sys_pwritev+0x120/0x170 fs/read_write.c:1135
 do_syscall_64+0x152/0x230 arch/x86/entry/common.c:287
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Bytes 4-1023 of 1024 are uninitialized
Memory access starts at ffff880159c69000
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