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BUG: KMSAN: uninit-value in copyout lib/iov_iter.c:140 [inline]
BUG: KMSAN: uninit-value in _copy_to_iter+0x45f/0x2800 lib/iov_iter.c:571
CPU: 1 PID: 8009 Comm: syz-executor2 Not tainted 4.17.0+ #3
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+0x135/0x1e0 mm/kmsan/kmsan.c:1177
 kmsan_copy_to_user+0x75/0x160 mm/kmsan/kmsan.c:1219
 copyout lib/iov_iter.c:140 [inline]
 _copy_to_iter+0x45f/0x2800 lib/iov_iter.c:571
 copy_to_iter include/linux/uio.h:106 [inline]
 vhost_chr_read_iter+0x7b3/0xc30 drivers/vhost/vhost.c:1107
 vhost_net_chr_read_iter+0xf6/0x130 drivers/vhost/net.c:1381
 call_read_iter include/linux/fs.h:1778 [inline]
 new_sync_read fs/read_write.c:406 [inline]
 __vfs_read+0x775/0x9d0 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+0x15b/0x230 arch/x86/entry/common.c:287
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x4559f9
RSP: 002b:00007f1776139c68 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
RAX: ffffffffffffffda RBX: 00007f177613a6d4 RCX: 00000000004559f9
RDX: 000000000000004a RSI: 0000000020000040 RDI: 0000000000000013
RBP: 000000000072bea0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 00000000004bfbb0 R14: 00000000004cfa60 R15: 0000000000000000

Uninit was created at:
 kmsan_save_stack_with_flags mm/kmsan/kmsan.c:279 [inline]
 kmsan_internal_poison_shadow+0xb8/0x1b0 mm/kmsan/kmsan.c:189
 kmsan_kmalloc+0x94/0x100 mm/kmsan/kmsan.c:315
 __kmalloc+0x13a/0x350 mm/slub.c:3818
 kmalloc include/linux/slab.h:517 [inline]
 vhost_new_msg drivers/vhost/vhost.c:2345 [inline]
 vhost_iotlb_miss drivers/vhost/vhost.c:1127 [inline]
 translate_desc+0xbef/0x1120 drivers/vhost/vhost.c:1834
 __vhost_get_user_slow drivers/vhost/vhost.c:812 [inline]
 __vhost_get_user drivers/vhost/vhost.c:846 [inline]
 vhost_update_used_flags+0x469/0x8d0 drivers/vhost/vhost.c:1720
 vhost_vq_init_access+0x173/0xa20 drivers/vhost/vhost.c:1768
 vhost_net_set_backend drivers/vhost/net.c:1182 [inline]
 vhost_net_ioctl+0x2217/0x3450 drivers/vhost/net.c:1338
 vfs_ioctl fs/ioctl.c:46 [inline]
 do_vfs_ioctl+0xcbd/0x24b0 fs/ioctl.c:686
 ksys_ioctl fs/ioctl.c:701 [inline]
 __do_sys_ioctl fs/ioctl.c:708 [inline]
 __se_sys_ioctl fs/ioctl.c:706 [inline]
 __x64_sys_ioctl+0x280/0x320 fs/ioctl.c:706
 do_syscall_64+0x15b/0x230 arch/x86/entry/common.c:287
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Bytes 4-7 of 72 are uninitialized
Memory access starts at ffff88013a9f3000
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