Re: [syzbot] [rdma?] KMSAN: uninit-value in ib_nl_handle_ip_res_resp

["yanjun.zhu" <yanjun.zhu@linux.dev>]

On 9/30/25 8:02 PM, Kohei Enju wrote:
> On Tue, 30 Sep 2025 13:29:32 -0700, syzbot wrote:
> 
>> Hello,
>>
>> syzbot found the following issue on:
>>
>> HEAD commit:    1896ce8eb6c6 Merge tag 'fsverity-for-linus' of git://git.k..
>> git tree:       upstream
>> console output: https://syzkaller.appspot.com/x/log.txt?x=153d0092580000
>> kernel config:  https://syzkaller.appspot.com/x/.config?x=6eca10e0cdef44f
>> 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
>> userspace arch: i386
>>
>> Unfortunately, I don't have any reproducer for this issue yet.
>>
>> Downloadable assets:
>> disk image: https://storage.googleapis.com/syzbot-assets/d0fbab3c0b62/disk-1896ce8e.raw.xz
>> vmlinux: https://storage.googleapis.com/syzbot-assets/71c7b444e106/vmlinux-1896ce8e.xz
>> kernel image: https://storage.googleapis.com/syzbot-assets/96a4aa63999d/bzImage-1896ce8e.xz
>>
>> IMPORTANT: if you fix the issue, please add the following tag to the commit:
>> Reported-by: syzbot+938fcd548c303fe33c1a@syzkaller.appspotmail.com
>>
>> netlink: 8 bytes leftover after parsing attributes in process `syz.8.3246'.
>> =====================================================
>> 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:2279
>> vprintk_emit+0x307/0xcd0 kernel/printk/printk.c:2426
>> vprintk_default+0x3f/0x50 kernel/printk/printk.c:2465
>> vprintk+0x36/0x50 kernel/printk/printk_safe.c:82
>> _printk+0x17e/0x1b0 kernel/printk/printk.c:2475
>> ib_nl_process_good_ip_rsep drivers/infiniband/core/addr.c:128 [inline]
> 
> I see when gid is not initialized in nla_for_each_attr loop, this should
> return early.

GID is a globally unique 128-bit identifier for an RDMA port, used for 
addressing and routing in InfiniBand or RoCE networks. It’s crucial for 
establishing RDMA connections across subnets or Ethernet networks. IMO, 
we do not just return when gid is not found. We should find out why the 
GID does not exist if I get you correctly.

Then we can fix this problem where the GID can not be added into GID table.

It is just my 2 cent advice.

Yanjun.Zhu

> 
> I think the splat occurrs when gid is not found, so a simple fix might
> be like:
> 
> diff --git a/drivers/infiniband/core/addr.c b/drivers/infiniband/core/addr.c
> index be0743dac3ff..c03a308bcda5 100644
> --- a/drivers/infiniband/core/addr.c
> +++ b/drivers/infiniband/core/addr.c
> @@ -103,15 +103,21 @@ static void ib_nl_process_good_ip_rsep(const struct nlmsghdr *nlh)
>          struct addr_req *req;
>          int len, rem;
>          int found = 0;
> +       bool gid_found = false;
> 
>          head = (const struct nlattr *)nlmsg_data(nlh);
>          len = nlmsg_len(nlh);
> 
>          nla_for_each_attr(curr, head, len, rem) {
> -               if (curr->nla_type == LS_NLA_TYPE_DGID)
> +               if (curr->nla_type == LS_NLA_TYPE_DGID) {
>                          memcpy(&gid, nla_data(curr), nla_len(curr));
> +                       gid_found = true;
> +               }
>          }
> 
> +       if (!gid_found)
> +               return;
> +
>          spin_lock_bh(&lock);
>          list_for_each_entry(req, &req_list, list) {
>                  if (nlh->nlmsg_seq != req->seq)
> 
>> 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:714 [inline]
>> __sock_sendmsg+0x333/0x3d0 net/socket.c:729
>> ____sys_sendmsg+0x7e0/0xd80 net/socket.c:2617
>> ___sys_sendmsg+0x271/0x3b0 net/socket.c:2671
>> __sys_sendmsg+0x1aa/0x300 net/socket.c:2703
>> __compat_sys_sendmsg net/compat.c:346 [inline]
>> __do_compat_sys_sendmsg net/compat.c:353 [inline]
>> __se_compat_sys_sendmsg net/compat.c:350 [inline]
>> __ia32_compat_sys_sendmsg+0xa4/0x100 net/compat.c:350
>> ia32_sys_call+0x3f6c/0x4310 arch/x86/include/generated/asm/syscalls_32.h:371
>> do_syscall_32_irqs_on arch/x86/entry/syscall_32.c:83 [inline]
>> __do_fast_syscall_32+0xb0/0x150 arch/x86/entry/syscall_32.c:306
>> 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 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: 17455 Comm: syz.8.3246 Not tainted syzkaller #0 PREEMPT(none)
>> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
>> =====================================================
>>
>>
>> ---
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>>
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