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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: 7744 Comm: syz-executor5 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+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:1104
 vhost_net_chr_read_iter+0xf6/0x130 drivers/vhost/net.c:1370
 do_iter_readv_writev+0x84d/0xa00 include/linux/fs.h:1778
 do_iter_read+0x303/0xd70 fs/read_write.c:922
 vfs_readv fs/read_write.c:986 [inline]
 do_readv+0x295/0x5f0 fs/read_write.c:1019
 __do_sys_readv fs/read_write.c:1106 [inline]
 __se_sys_readv fs/read_write.c:1103 [inline]
 __x64_sys_readv+0xe1/0x120 fs/read_write.c:1103
 do_syscall_64+0x152/0x230 arch/x86/entry/common.c:287
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x455a09
RSP: 002b:00007f8de3935c68 EFLAGS: 00000246 ORIG_RAX: 0000000000000013
RAX: ffffffffffffffda RBX: 00007f8de39366d4 RCX: 0000000000455a09
RDX: 0000000000000001 RSI: 0000000020000040 RDI: 0000000000000013
RBP: 000000000072bea0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 000000000000056b R14: 00000000006fd2a8 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+0x141/0x350 mm/slub.c:3818
 kmalloc include/linux/slab.h:517 [inline]
 vhost_new_msg drivers/vhost/vhost.c:2342 [inline]
 vhost_iotlb_miss drivers/vhost/vhost.c:1124 [inline]
 translate_desc+0xbef/0x1120 drivers/vhost/vhost.c:1831
 __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:1717
 vhost_vq_init_access+0x173/0xa20 drivers/vhost/vhost.c:1765
 vhost_net_set_backend drivers/vhost/net.c:1171 [inline]
 vhost_net_ioctl+0x2212/0x3450 drivers/vhost/net.c:1327
 vfs_ioctl fs/ioctl.c:46 [inline]
 do_vfs_ioctl+0xaf8/0x2410 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+0x152/0x230 arch/x86/entry/common.c:287
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Bytes 4-7 of 72 are uninitialized
Memory access starts at ffff880133794ae0
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