Re: [syzbot] [usb?] [net?] KMSAN: uninit-value in rtl8150_open (2)

[Kohei Enju]

+ Iwashima-san

On Tue, 24 Mar 2026 19:40:28 -0700, syzbot wrote:
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit:    c612261bedd6 Merge tag 'io_uring-7.0-20260320' of git://gi..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=155801d6580000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=963de479f54c6dbb
> dashboard link: https://syzkaller.appspot.com/bug?extid=9db6c624635564ad813c
> 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/aa2bdf537bf6/disk-c612261b.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/8fcd98072431/vmlinux-c612261b.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/737b94c52155/bzImage-c612261b.xz
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+9db6c624635564ad813c@xxxxxxxxxxxxxxxxxxxxxxxxx
>
> usb 2-1: device reset failed
> =====================================================
> BUG: KMSAN: uninit-value in set_carrier drivers/net/usb/rtl8150.c:726 [inline]
> BUG: KMSAN: uninit-value in rtl8150_open+0x1131/0x1360 drivers/net/usb/rtl8150.c:763
>  set_carrier drivers/net/usb/rtl8150.c:726 [inline]
>  rtl8150_open+0x1131/0x1360 drivers/net/usb/rtl8150.c:763
>  __dev_open+0x8e3/0xd40 net/core/dev.c:1702
>  __dev_change_flags+0x32f/0x950 net/core/dev.c:9764
>  netif_change_flags+0x8d/0x1e0 net/core/dev.c:9827
>  dev_change_flags+0x18c/0x320 net/core/dev_api.c:68
>  devinet_ioctl+0x10dd/0x25a0 net/ipv4/devinet.c:1199
>  inet_ioctl+0x4c0/0x6f0 net/ipv4/af_inet.c:1015
>  sock_do_ioctl net/socket.c:1254 [inline]
>  sock_ioctl+0x769/0x1140 net/socket.c:1375
>  vfs_ioctl fs/ioctl.c:51 [inline]
>  __do_sys_ioctl fs/ioctl.c:597 [inline]
>  __se_sys_ioctl+0x23c/0x400 fs/ioctl.c:583
>  __x64_sys_ioctl+0x97/0xe0 fs/ioctl.c:583
>  x64_sys_call+0x1975/0x3ea0 arch/x86/include/generated/asm/syscalls_64.h:17
>  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 tmp.i created at:
>  set_carrier drivers/net/usb/rtl8150.c:723 [inline]
>  rtl8150_open+0xc26/0x1360 drivers/net/usb/rtl8150.c:763
>  __dev_open+0x8e3/0xd40 net/core/dev.c:1702

I see Iwashima-san was previously working on this issue here:
  https://lore.kernel.org/all/20250827233108.3768855-1-kuniyu@xxxxxxxxxx/T/

The issue seems to be that set_carrier() ignores the return value of
get_registers() and may use an uninitialized tmp.

rtl8150 appears to have other call sites that use get_registers() the
same way as mentioned in the thread above.