Re: [syzbot] [modules?] KMSAN: uninit-value in __request_module (6)

[Petr Pavlu <petr.pavlu@suse.com>]

On 2/12/25 14:41, syzbot wrote:
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    febbc555cf0f Merge tag 'nfsd-6.14-1' of git://git.kernel.o..
> git tree:       upstream
> console+strace: https://syzkaller.appspot.com/x/log.txt?x=137a78e4580000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=48f90cac5eea091a
> dashboard link: https://syzkaller.appspot.com/bug?extid=1fcd957a82e3a1baa94d
> compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=177a78e4580000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=16adc3f8580000
> 
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/f90f94285615/disk-febbc555.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/b8a8bb66806c/vmlinux-febbc555.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/c8af6c511559/bzImage-febbc555.xz
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+1fcd957a82e3a1baa94d@syzkaller.appspotmail.com
> 
> =====================================================
> BUG: KMSAN: uninit-value in string_nocheck lib/vsprintf.c:633 [inline]
> BUG: KMSAN: uninit-value in string+0x3ec/0x5f0 lib/vsprintf.c:714
>  string_nocheck lib/vsprintf.c:633 [inline]
>  string+0x3ec/0x5f0 lib/vsprintf.c:714
>  vsnprintf+0xa5d/0x1960 lib/vsprintf.c:2843
>  __request_module+0x252/0x9f0 kernel/module/kmod.c:149
>  team_mode_get drivers/net/team/team_core.c:480 [inline]
>  team_change_mode drivers/net/team/team_core.c:607 [inline]
>  team_mode_option_set+0x437/0x970 drivers/net/team/team_core.c:1401
>  team_option_set drivers/net/team/team_core.c:375 [inline]
>  team_nl_options_set_doit+0x1339/0x1f90 drivers/net/team/team_core.c:2661
>  genl_family_rcv_msg_doit net/netlink/genetlink.c:1115 [inline]
>  genl_family_rcv_msg net/netlink/genetlink.c:1195 [inline]
>  genl_rcv_msg+0x1214/0x12c0 net/netlink/genetlink.c:1210
>  netlink_rcv_skb+0x375/0x650 net/netlink/af_netlink.c:2543
>  genl_rcv+0x40/0x60 net/netlink/genetlink.c:1219
>  netlink_unicast_kernel net/netlink/af_netlink.c:1322 [inline]
>  netlink_unicast+0xf52/0x1260 net/netlink/af_netlink.c:1348
>  netlink_sendmsg+0x10da/0x11e0 net/netlink/af_netlink.c:1892
>  sock_sendmsg_nosec net/socket.c:718 [inline]
>  __sock_sendmsg+0x30f/0x380 net/socket.c:733
>  ____sys_sendmsg+0x877/0xb60 net/socket.c:2573
>  ___sys_sendmsg+0x28d/0x3c0 net/socket.c:2627
>  __sys_sendmsg net/socket.c:2659 [inline]
>  __do_sys_sendmsg net/socket.c:2664 [inline]
>  __se_sys_sendmsg net/socket.c:2662 [inline]
>  __x64_sys_sendmsg+0x212/0x3c0 net/socket.c:2662
>  x64_sys_call+0x2ed6/0x3c30 arch/x86/include/generated/asm/syscalls_64.h:47
>  do_syscall_x64 arch/x86/entry/common.c:52 [inline]
>  do_syscall_64+0xcd/0x1e0 arch/x86/entry/common.c:83
>  entry_SYSCALL_64_after_hwframe+0x77/0x7f
> 
> Uninit was created at:
>  slab_post_alloc_hook mm/slub.c:4121 [inline]
>  slab_alloc_node mm/slub.c:4164 [inline]
>  kmem_cache_alloc_node_noprof+0x907/0xe00 mm/slub.c:4216
>  kmalloc_reserve+0x13d/0x4a0 net/core/skbuff.c:587
>  __alloc_skb+0x363/0x7b0 net/core/skbuff.c:678
>  alloc_skb include/linux/skbuff.h:1331 [inline]
>  netlink_alloc_large_skb+0x1b4/0x280 net/netlink/af_netlink.c:1196
>  netlink_sendmsg+0xa96/0x11e0 net/netlink/af_netlink.c:1867
>  sock_sendmsg_nosec net/socket.c:718 [inline]
>  __sock_sendmsg+0x30f/0x380 net/socket.c:733
>  ____sys_sendmsg+0x877/0xb60 net/socket.c:2573
>  ___sys_sendmsg+0x28d/0x3c0 net/socket.c:2627
>  __sys_sendmsg net/socket.c:2659 [inline]
>  __do_sys_sendmsg net/socket.c:2664 [inline]
>  __se_sys_sendmsg net/socket.c:2662 [inline]
>  __x64_sys_sendmsg+0x212/0x3c0 net/socket.c:2662
>  x64_sys_call+0x2ed6/0x3c30 arch/x86/include/generated/asm/syscalls_64.h:47
>  do_syscall_x64 arch/x86/entry/common.c:52 [inline]
>  do_syscall_64+0xcd/0x1e0 arch/x86/entry/common.c:83
>  entry_SYSCALL_64_after_hwframe+0x77/0x7f
> 
> CPU: 0 UID: 0 PID: 5814 Comm: syz-executor989 Not tainted 6.14.0-rc2-syzkaller-00034-gfebbc555cf0f #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 12/27/2024
> =====================================================

For the record in linux-modules, Eric Dumazet posted a fix for this
issue at:
https://lore.kernel.org/netdev/20250212134928.1541609-1-edumazet@google.com/

-- Petr