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BUG: KMSAN: kernel-infoleak in _copy_to_user+0x1a4/0x250 lib/usercopy.c:32
CPU: 1 PID: 15134 Comm: syz-executor5 Not tainted 4.20.0-rc5+ #112
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+0x1c9/0x220 lib/dump_stack.c:113
 kmsan_report+0x12d/0x290 mm/kmsan/kmsan.c:684
 kmsan_internal_check_memory+0x32a/0xa50 mm/kmsan/kmsan.c:744
 kmsan_copy_to_user+0x8d/0xa0 mm/kmsan/kmsan_hooks.c:620
 _copy_to_user+0x1a4/0x250 lib/usercopy.c:32
 copy_to_user include/linux/uaccess.h:177 [inline]
 userfaultfd_read+0x235e/0x2a20 fs/userfaultfd.c:1194
 do_loop_readv_writev fs/read_write.c:700 [inline]
 do_iter_read+0x879/0xe00 fs/read_write.c:924
 vfs_readv fs/read_write.c:986 [inline]
 do_readv+0x2a7/0x640 fs/read_write.c:1019
 __do_sys_readv fs/read_write.c:1106 [inline]
 __se_sys_readv+0x9b/0xb0 fs/read_write.c:1103
 __x64_sys_readv+0x4a/0x70 fs/read_write.c:1103
 do_syscall_64+0xcd/0x110 arch/x86/entry/common.c:291
 entry_SYSCALL_64_after_hwframe+0x63/0xe7
RIP: 0033:0x457679
Code: fd b3 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 cb b3 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007fa5b0fa8c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000013
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000457679
RDX: 0000000000000001 RSI: 0000000020000080 RDI: 0000000000000004
RBP: 000000000072bfa0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007fa5b0fa96d4
R13: 00000000004c39f7 R14: 00000000004d66b8 R15: 00000000ffffffff

Uninit was created at:
No stack

Byte 8 of 32 is uninitialized
Memory access of size 32 starts at ffff88805102fb88
Data copied to user address 0000000020000000
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