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

[syzbot]

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+938fcd...@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]
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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[Kohei Enju]

I see when gid is not initialized in nla_for_each_attr loop, this should
return early.

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)

[yanjun.zhu]

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

[Kohei Enju]

>addressing and routing in InfiniBand or RoCE networks. It\u2019s 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.

Indeed, I think you're right.
Considering that ib_nl_is_good_ip_resp() returns true, the fact that GID
doesn't exist seems weird and we should investigate the cause.

[syzbot]

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+938fcd...@syzkaller.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
=====================================================


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