Re: [PATCH net] net/smc: Initialize smc hashtables before registering users
From: Dust Li <dust.li@linux.alibaba.com>
Date: 2025-12-17 15:25:47
Also in:
linux-rdma, linux-s390, stable
On 2025-12-17 12:48:19, Alexandra Winter wrote:
During initialisation of the SMC module initialize smc_v4/6_hashinfo before calling smc_nl_init(), proto_register() or sock_register(), to avoid a race that can cause use of an uninitialised pointer in case an smc protocol is called before the module is done initialising. syzbot report: KASAN: null-ptr-deref in range [0x0000000000000008-0x000000000000000f] Call Trace: <TASK> smc_diag_dump+0x59/0xa0 net/smc/smc_diag.c:236 netlink_dump+0x647/0xd80 net/netlink/af_netlink.c:2325 __netlink_dump_start+0x59f/0x780 net/netlink/af_netlink.c:2440 netlink_dump_start include/linux/netlink.h:339 [inline] smc_diag_handler_dump+0x1ab/0x250 net/smc/smc_diag.c:251 sock_diag_rcv_msg+0x3dc/0x5f0 netlink_rcv_skb+0x1e3/0x430 net/netlink/af_netlink.c:2550 netlink_unicast_kernel net/netlink/af_netlink.c:1331 [inline] netlink_unicast+0x7f0/0x990 net/netlink/af_netlink.c:1357 netlink_sendmsg+0x8e4/0xcb0 net/netlink/af_netlink.c:1901
I don't think this is related to smc_nl_init(). Here the calltrace is smc_diag_dump(), which was registered in sock_diag_register(&smc_diag_handler). But smc_nl_init() is registering the general netlink in SMC, which is unrelated to smc_diag_dump(). I think the root cause should be related to the initializing between smc_diag.ko and smc_v4/6_hashinfo.ht. The change in your previous patch 'dibs: Register smc as dibs_client' may change the possiblity to this bug. Best regards, Dust
quoted hunk ↗ jump to hunk
Fixes: f16a7dd5cf27 ("smc: netlink interface for SMC sockets") Reported-by: syzbot+f69bfae0a4eb29976e44@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=f69bfae0a4eb29976e44 Signed-off-by: Alexandra Winter <wintera@linux.ibm.com> --- net/smc/af_smc.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)diff --git a/net/smc/af_smc.c b/net/smc/af_smc.c index f97f77b041d9..b0f4405fb714 100644 --- a/net/smc/af_smc.c +++ b/net/smc/af_smc.c@@ -3524,6 +3524,9 @@ static int __init smc_init(void)goto out_pernet_subsys_stat; smc_clc_init(); + INIT_HLIST_HEAD(&smc_v4_hashinfo.ht); + INIT_HLIST_HEAD(&smc_v6_hashinfo.ht); + rc = smc_nl_init(); if (rc) goto out_ism;@@ -3581,8 +3584,6 @@ static int __init smc_init(void)pr_err("%s: sock_register fails with %d\n", __func__, rc); goto out_proto6; } - INIT_HLIST_HEAD(&smc_v4_hashinfo.ht); - INIT_HLIST_HEAD(&smc_v6_hashinfo.ht); rc = smc_ib_register_client(); if (rc) { -- 2.51.0