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

[syzbot]

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+4b1bd5...@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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[syzbot]

syzbot has found a reproducer for 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=177aec02580000

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

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=120fc722580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=10faec02580000

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+4b1bd5...@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

native_irq_enable arch/x86/include/asm/irqflags.h:42 [inline]
arch_local_irq_enable arch/x86/include/asm/irqflags.h:119 [inline]
raw_spin_rq_unlock_irq kernel/sched/sched.h:1629 [inline]
finish_lock_switch kernel/sched/core.c:5032 [inline]
finish_task_switch+0x11b/0x8b0 kernel/sched/core.c:5150
context_switch kernel/sched/core.c:5298 [inline]
__schedule+0x273e/0x8650 kernel/sched/core.c:6907
schedule_idle+0x5a/0x90 kernel/sched/core.c:7030
do_idle+0x748/0x760 kernel/sched/idle.c:360
cpu_startup_entry+0x5f/0x80 kernel/sched/idle.c:430
start_secondary+0xcc/0xd0 arch/x86/kernel/smpboot.c:312
common_startup_64+0x13e/0x147

Local variable reuse.i created at:
mas_wr_node_store lib/maple_tree.c:3495 [inline]
mas_wr_store_entry+0x14bd/0x96d0 lib/maple_tree.c:3764
mas_store_prealloc+0x1834/0x1e60 lib/maple_tree.c:5169

CPU: 1 UID: 0 PID: 0 Comm: swapper/1 Not tainted syzkaller #0 PREEMPT(full)

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
=====================================================


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