linux-kernel - Re: [syzbot] [rdma?] KMSAN: uninit-value in ib_nl_handle_ip_res

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Message-ID: <68fcfd75.050a0220.346f24.02ff.GAE@google.com>
Date: Sat, 25 Oct 2025 09:40:21 -0700
From: syzbot <syzbot+938fcd548c303fe33c1a@...kaller.appspotmail.com>
To: enjuk@...zon.com, jgg@...pe.ca, leon@...nel.org, 
	linux-kernel@...r.kernel.org, linux-rdma@...r.kernel.org, 
	syzkaller-bugs@...glegroups.com, yanjun.zhu@...ux.dev
Subject: Re: [syzbot] [rdma?] KMSAN: uninit-value in ib_nl_handle_ip_res_resp

syzbot has found a reproducer for the following issue on:

HEAD commit:    566771afc7a8 Merge tag 'v6.18-rc2-smb-server-fixes' of git..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=12f017e2580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=dce7eac4016da338
dashboard link: https://syzkaller.appspot.com/bug?extid=938fcd548c303fe33c1a
compiler:       Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=13714be2580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=100b5d2f980000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/bc5e0bc7a5d9/disk-566771af.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/6b2be7ad3b45/vmlinux-566771af.xz
kernel image: https://storage.googleapis.com/syzbot-assets/09a4929333f1/bzImage-566771af.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+938fcd548c303fe33c1a@...kaller.appspotmail.com

netlink: 8 bytes leftover after parsing attributes in process `syz.0.18'.
=====================================================
BUG: KMSAN: uninit-value in hex_byte_pack include/linux/hex.h:13 [inline]
BUG: KMSAN: uninit-value in ip6_string+0xef4/0x13a0 lib/vsprintf.c:1490
 hex_byte_pack include/linux/hex.h:13 [inline]
 ip6_string+0xef4/0x13a0 lib/vsprintf.c:1490
 ip6_addr_string+0x18a/0x3e0 lib/vsprintf.c:1509
 ip_addr_string+0x245/0xee0 lib/vsprintf.c:1633
 pointer+0xc09/0x1bd0 lib/vsprintf.c:2542
 vsnprintf+0xf8a/0x1bd0 lib/vsprintf.c:2930
 vprintk_store+0x3ae/0x1530 kernel/printk/printk.c:2252
 vprintk_emit+0x21a/0xb60 kernel/printk/printk.c:2399
 vprintk_default+0x3f/0x50 kernel/printk/printk.c:2438
 vprintk+0x36/0x50 kernel/printk/printk_safe.c:82
 _printk+0x17e/0x1b0 kernel/printk/printk.c:2448
 ib_nl_process_good_ip_rsep drivers/infiniband/core/addr.c:128 [inline]
 ib_nl_handle_ip_res_resp+0x963/0x9d0 drivers/infiniband/core/addr.c:141
 rdma_nl_rcv_msg drivers/infiniband/core/netlink.c:-1 [inline]
 rdma_nl_rcv_skb drivers/infiniband/core/netlink.c:239 [inline]
 rdma_nl_rcv+0xefa/0x11c0 drivers/infiniband/core/netlink.c:259
 netlink_unicast_kernel net/netlink/af_netlink.c:1320 [inline]
 netlink_unicast+0xf04/0x12b0 net/netlink/af_netlink.c:1346
 netlink_sendmsg+0x10b3/0x1250 net/netlink/af_netlink.c:1896
 sock_sendmsg_nosec net/socket.c:727 [inline]
 __sock_sendmsg+0x333/0x3d0 net/socket.c:742
 ____sys_sendmsg+0x7e0/0xd80 net/socket.c:2630
 ___sys_sendmsg+0x271/0x3b0 net/socket.c:2684
 __sys_sendmsg net/socket.c:2716 [inline]
 __do_sys_sendmsg net/socket.c:2721 [inline]
 __se_sys_sendmsg net/socket.c:2719 [inline]
 __x64_sys_sendmsg+0x211/0x3e0 net/socket.c:2719
 x64_sys_call+0x1dfd/0x3e30 arch/x86/include/generated/asm/syscalls_64.h:47
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd9/0xfa0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Local variable gid.i created at:
 ib_nl_process_good_ip_rsep drivers/infiniband/core/addr.c:102 [inline]
 ib_nl_handle_ip_res_resp+0x254/0x9d0 drivers/infiniband/core/addr.c:141
 rdma_nl_rcv_msg drivers/infiniband/core/netlink.c:-1 [inline]
 rdma_nl_rcv_skb drivers/infiniband/core/netlink.c:239 [inline]
 rdma_nl_rcv+0xefa/0x11c0 drivers/infiniband/core/netlink.c:259

CPU: 0 UID: 0 PID: 6093 Comm: syz.0.18 Not tainted syzkaller #0 PREEMPT(none) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
=====================================================

---
If you want syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
If you attach or paste a git patch, syzbot will apply it before testing.