[syzbot] [kernel?] KMSAN: uninit-value in __flush_smp_call_function_queue

[syzbot <syzbot+4b1bd55fba6260160779@syzkaller.appspotmail.com>]

Hello,

syzbot found the following issue on:

HEAD commit:    ca4ee40bf13d Partly revert "drm/hyperv: Remove reference t..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=114ac722580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=4b4f2aab682301f1
dashboard link: https://syzkaller.appspot.com/bug?extid=4b1bd55fba6260160779
compiler:       Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/68f5e4558a91/disk-ca4ee40b.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/ea1eab60444d/vmlinux-ca4ee40b.xz
kernel image: https://storage.googleapis.com/syzbot-assets/cc7e3debdec4/bzImage-ca4ee40b.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+4b1bd55fba6260160779@syzkaller.appspotmail.com

=====================================================
BUG: KMSAN: uninit-value in __flush_smp_call_function_queue+0x362/0x18e0 kernel/smp.c:535
 __flush_smp_call_function_queue+0x362/0x18e0 kernel/smp.c:535
 generic_smp_call_function_single_interrupt+0x1c/0x30 kernel/smp.c:463
 __sysvec_call_function_single+0x4b/0x3e0 arch/x86/kernel/smp.c:271
 instr_sysvec_call_function_single arch/x86/kernel/smp.c:266 [inline]
 sysvec_call_function_single+0x7c/0x90 arch/x86/kernel/smp.c:266
 asm_sysvec_call_function_single+0x1f/0x30 arch/x86/include/asm/idtentry.h:704
 kmsan_get_metadata+0x12e/0x160 mm/kmsan/shadow.c:148
 kmsan_get_shadow_origin_ptr+0x35/0xb0 mm/kmsan/shadow.c:97
 get_shadow_origin_ptr mm/kmsan/instrumentation.c:38 [inline]
 __msan_metadata_ptr_for_load_8+0x24/0x40 mm/kmsan/instrumentation.c:94
 on_stack+0x5f/0x1f0 arch/x86/include/asm/stacktrace.h:56
 update_stack_state+0xa7/0x1c0 arch/x86/kernel/unwind_frame.c:228
 unwind_next_frame+0x116/0x350 arch/x86/kernel/unwind_frame.c:315
 arch_stack_walk+0x1b0/0x280 arch/x86/kernel/stacktrace.c:25
 stack_trace_save+0xc2/0x100 kernel/stacktrace.c:122
 ref_tracker_alloc+0x1b2/0x7a0 lib/ref_tracker.c:277
 __netdev_tracker_alloc include/linux/netdevice.h:4403 [inline]
 netdev_tracker_alloc include/linux/netdevice.h:4415 [inline]
 netdev_get_by_index+0xf6/0x1b0 net/core/dev.c:1020
 fib6_nh_init+0x172/0x32c0 net/ipv6/route.c:3600
 ip6_route_info_create_nh+0x4e4/0xf60 net/ipv6/route.c:3900
 ip6_route_add+0x159/0x4a0 net/ipv6/route.c:3952
 addrconf_add_mroute net/ipv6/addrconf.c:2552 [inline]
 addrconf_add_dev+0x6af/0x790 net/ipv6/addrconf.c:2570
 inet6_addr_add+0x2d5/0x1570 net/ipv6/addrconf.c:3032
 inet6_rtm_newaddr+0x1a0f/0x1dd0 net/ipv6/addrconf.c:5064
 rtnetlink_rcv_msg+0x106f/0x14b0 net/core/rtnetlink.c:6958
 netlink_rcv_skb+0x54d/0x680 net/netlink/af_netlink.c:2550
 rtnetlink_rcv+0x35/0x40 net/core/rtnetlink.c:6985
 netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline]
 netlink_unicast+0xf04/0x12b0 net/netlink/af_netlink.c:1344
 netlink_sendmsg+0x10b2/0x1250 net/netlink/af_netlink.c:1894
 sock_sendmsg_nosec net/socket.c:727 [inline]
 __sock_sendmsg net/socket.c:742 [inline]
 __sys_sendto+0xa77/0xb90 net/socket.c:2206
 __do_sys_sendto net/socket.c:2213 [inline]
 __se_sys_sendto net/socket.c:2209 [inline]
 __x64_sys_sendto+0x130/0x200 net/socket.c:2209
 x64_sys_call+0x39a0/0x3ea0 arch/x86/include/generated/asm/syscalls_64.h:45
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x134/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Local variable prefix created at:
 record_print_text+0xca/0x8e0 kernel/printk/printk.c:1420
 printk_get_next_message+0xc7c/0x1250 kernel/printk/printk.c:3072

CPU: 0 UID: 0 PID: 15335 Comm: syz-executor Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
=====================================================


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