linux-kernel - [syzbot] [net?] KMSAN: uninit-value in __ipv6_dev_mc

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Message-ID: <681e5e9d.050a0220.a19a9.013c.GAE@google.com>
Date: Fri, 09 May 2025 12:59:25 -0700
From: syzbot <syzbot+4472ecce287501aa597a@...kaller.appspotmail.com>
To: davem@...emloft.net, dsahern@...nel.org, edumazet@...gle.com, 
	horms@...nel.org, kuba@...nel.org, linux-kernel@...r.kernel.org, 
	netdev@...r.kernel.org, pabeni@...hat.com, syzkaller-bugs@...glegroups.com
Subject: [syzbot] [net?] KMSAN: uninit-value in __ipv6_dev_mc_dec (2)

Hello,

syzbot found the following issue on:

HEAD commit:    02ddfb981de8 Merge tag 'scsi-fixes' of git://git.kernel.or..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=13a14670580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=9dc42c34a3f5c357
dashboard link: https://syzkaller.appspot.com/bug?extid=4472ecce287501aa597a
compiler:       Debian clang version 20.1.2 (++20250402124445+58df0ef89dd6-1~exp1~20250402004600.97), Debian LLD 20.1.2
userspace arch: i386

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/7dc8afe7520f/disk-02ddfb98.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/3194559250c2/vmlinux-02ddfb98.xz
kernel image: https://storage.googleapis.com/syzbot-assets/86c7c494f08f/bzImage-02ddfb98.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+4472ecce287501aa597a@...kaller.appspotmail.com

=====================================================
BUG: KMSAN: uninit-value in __ipv6_dev_mc_dec+0x68a/0xd30 net/ipv6/mcast.c:1014
 __ipv6_dev_mc_dec+0x68a/0xd30 net/ipv6/mcast.c:1014
 addrconf_leave_solict net/ipv6/addrconf.c:2254 [inline]
 __ipv6_ifa_notify+0xf97/0x1990 net/ipv6/addrconf.c:6299
 addrconf_ifdown+0x1c61/0x32e0 net/ipv6/addrconf.c:3978
 addrconf_notify+0x183/0x1d10 net/ipv6/addrconf.c:3777
 notifier_call_chain kernel/notifier.c:85 [inline]
 raw_notifier_call_chain+0xdd/0x410 kernel/notifier.c:453
 call_netdevice_notifiers_info+0x1ac/0x2b0 net/core/dev.c:2176
 call_netdevice_notifiers_extack net/core/dev.c:2214 [inline]
 call_netdevice_notifiers net/core/dev.c:2228 [inline]
 dev_close_many+0x52a/0x8f0 net/core/dev.c:1731
 unregister_netdevice_many_notify+0x1106/0x4970 net/core/dev.c:11952
 unregister_netdevice_many net/core/dev.c:12046 [inline]
 unregister_netdevice_queue+0x3b1/0x600 net/core/dev.c:11889
 unregister_netdevice include/linux/netdevice.h:3374 [inline]
 __tun_detach+0x16c8/0x20c0 drivers/net/tun.c:620
 tun_detach drivers/net/tun.c:636 [inline]
 tun_chr_close+0xb7/0x290 drivers/net/tun.c:3390
 __fput+0x608/0x1040 fs/file_table.c:465
 ____fput+0x25/0x30 fs/file_table.c:493
 task_work_run+0x206/0x2b0 kernel/task_work.c:227
 resume_user_mode_work+0x105/0x160 include/linux/resume_user_mode.h:50
 exit_to_user_mode_loop kernel/entry/common.c:114 [inline]
 exit_to_user_mode_prepare include/linux/entry-common.h:329 [inline]
 __syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline]
 syscall_exit_to_user_mode+0x7b/0xb0 kernel/entry/common.c:218
 __do_fast_syscall_32+0xbd/0x110 arch/x86/entry/syscall_32.c:309
 do_fast_syscall_32+0x38/0x80 arch/x86/entry/syscall_32.c:331
 do_SYSENTER_32+0x1f/0x30 arch/x86/entry/syscall_32.c:369
 entry_SYSENTER_compat_after_hwframe+0x84/0x8e

Local variable maddr.i created at:
 addrconf_leave_solict net/ipv6/addrconf.c:2248 [inline]
 __ipv6_ifa_notify+0xe6f/0x1990 net/ipv6/addrconf.c:6299
 addrconf_ifdown+0x1c61/0x32e0 net/ipv6/addrconf.c:3978

CPU: 1 UID: 0 PID: 10959 Comm: syz.4.717 Not tainted 6.15.0-rc3-syzkaller-00094-g02ddfb981de8 #0 PREEMPT(undef) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/29/2025
=====================================================


---
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