=====================================================
BUG: KMSAN: uninit-value in map_id_up_base kernel/user_namespace.c:335 [inline]
BUG: KMSAN: uninit-value in map_id_up kernel/user_namespace.c:365 [inline]
BUG: KMSAN: uninit-value in from_kgid+0x52e/0xbe0 kernel/user_namespace.c:481
 map_id_up_base kernel/user_namespace.c:335 [inline]
 map_id_up kernel/user_namespace.c:365 [inline]
 from_kgid+0x52e/0xbe0 kernel/user_namespace.c:481
 p9pdu_vwritef+0x18d0/0x5100 net/9p/protocol.c:405
 p9pdu_writef+0x240/0x290 net/9p/protocol.c:539
 p9pdu_vwritef+0x21ed/0x5100 net/9p/protocol.c:490
 p9_client_prepare_req+0xe64/0x16d0 net/9p/client.c:703
 p9_client_rpc+0x28b/0x1460 net/9p/client.c:734
 p9_client_setattr+0x113/0x2c0 net/9p/client.c:1894
 v9fs_vfs_setattr_dotl+0x7e2/0xd70 fs/9p/vfs_inode_dotl.c:588
 notify_change+0x1fde/0x2180 fs/attr.c:410
 chown_common+0x832/0xc70 fs/open.c:678
 do_fchownat+0x2df/0x4e0 fs/open.c:709
 ksys_lchown include/linux/syscalls.h:1335 [inline]
 __do_sys_lchown16 kernel/uid16.c:30 [inline]
 __se_sys_lchown16 kernel/uid16.c:28 [inline]
 __ia32_sys_lchown16+0x200/0x250 kernel/uid16.c:28
 do_syscall_32_irqs_on arch/x86/entry/common.c:114 [inline]
 __do_fast_syscall_32+0x96/0xf0 arch/x86/entry/common.c:180
 do_fast_syscall_32+0x34/0x70 arch/x86/entry/common.c:205
 do_SYSENTER_32+0x1b/0x20 arch/x86/entry/common.c:248
 entry_SYSENTER_compat_after_hwframe+0x4d/0x5c

Uninit was stored to memory at:
 v9fs_vfs_setattr_dotl+0x5a9/0xd70 fs/9p/vfs_inode_dotl.c:566
 notify_change+0x1fde/0x2180 fs/attr.c:410
 chown_common+0x832/0xc70 fs/open.c:678
 do_fchownat+0x2df/0x4e0 fs/open.c:709
 ksys_lchown include/linux/syscalls.h:1335 [inline]
 __do_sys_lchown16 kernel/uid16.c:30 [inline]
 __se_sys_lchown16 kernel/uid16.c:28 [inline]
 __ia32_sys_lchown16+0x200/0x250 kernel/uid16.c:28
 do_syscall_32_irqs_on arch/x86/entry/common.c:114 [inline]
 __do_fast_syscall_32+0x96/0xf0 arch/x86/entry/common.c:180
 do_fast_syscall_32+0x34/0x70 arch/x86/entry/common.c:205
 do_SYSENTER_32+0x1b/0x20 arch/x86/entry/common.c:248
 entry_SYSENTER_compat_after_hwframe+0x4d/0x5c

Local variable newattrs created at:
 chown_common+0x120/0xc70 fs/open.c:647
 do_fchownat+0x2df/0x4e0 fs/open.c:709

CPU: 0 PID: 31712 Comm: syz-executor.3 Not tainted 5.16.0-rc5-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
=====================================================