Re: [PATCH net v2] net/smc: fix general protection fault in __smc_diag_dump

Eric Dumazet
2025-10-17T05:54:44Z

On Thu, Oct 16, 2025 at 10:51 PM Kuniyuki Iwashima <kuniyu@google.com> wrote:
>
> From: Wang Liang <wangliang74@huawei.com>
> Date: Fri, 17 Oct 2025 10:48:27 +0800
> > The syzbot report a crash:
> >
> > Oops: general protection fault, probably for non-canonical address 0xfbd5a5d5a0000003: 0000 [#1] SMP KASAN NOPTI
> > KASAN: maybe wild-memory-access in range [0xdead4ead00000018-0xdead4ead0000001f]
> > CPU: 1 UID: 0 PID: 6949 Comm: syz.0.335 Not tainted syzkaller #0 PREEMPT(full)
> > Hardware name: Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
> > RIP: 0010:smc_diag_msg_common_fill net/smc/smc_diag.c:44 [inline]
> > RIP: 0010:__smc_diag_dump.constprop.0+0x3ca/0x2550 net/smc/smc_diag.c:89
> > Call Trace:
> > <TASK>
> > smc_diag_dump_proto+0x26d/0x420 net/smc/smc_diag.c:217
> > smc_diag_dump+0x27/0x90 net/smc/smc_diag.c:234
> > netlink_dump+0x539/0xd30 net/netlink/af_netlink.c:2327
> > __netlink_dump_start+0x6d6/0x990 net/netlink/af_netlink.c:2442
> > netlink_dump_start include/linux/netlink.h:341 [inline]
> > smc_diag_handler_dump+0x1f9/0x240 net/smc/smc_diag.c:251
> > __sock_diag_cmd net/core/sock_diag.c:249 [inline]
> > sock_diag_rcv_msg+0x438/0x790 net/core/sock_diag.c:285
> > netlink_rcv_skb+0x158/0x420 net/netlink/af_netlink.c:2552
> > netlink_unicast_kernel net/netlink/af_netlink.c:1320 [inline]
> > netlink_unicast+0x5a7/0x870 net/netlink/af_netlink.c:1346
> > netlink_sendmsg+0x8d1/0xdd0 net/netlink/af_netlink.c:1896
> > sock_sendmsg_nosec net/socket.c:714 [inline]
> > __sock_sendmsg net/socket.c:729 [inline]
> > ____sys_sendmsg+0xa95/0xc70 net/socket.c:2614
> > ___sys_sendmsg+0x134/0x1d0 net/socket.c:2668
> > __sys_sendmsg+0x16d/0x220 net/socket.c:2700
> > do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
> > do_syscall_64+0xcd/0x4e0 arch/x86/entry/syscall_64.c:94
> > entry_SYSCALL_64_after_hwframe+0x77/0x7f
> > </TASK>
> >
> > The process like this:
> >
> > (CPU1) | (CPU2)
> > ---------------------------------|-------------------------------
> > inet_create() |
> > // init clcsock to NULL |
> > sk = sk_alloc() |
> > |
> > // unexpectedly change clcsock |
> > inet_init_csk_locks() |
> > |
> > // add sk to hash table |
> > smc_inet_init_sock() |
> > smc_sk_init() |
> > smc_hash_sk() |
> > | // traverse the hash table
> > | smc_diag_dump_proto
> > | __smc_diag_dump()
> > | // visit wrong clcsock
> > | smc_diag_msg_common_fill()
> > // alloc clcsock |
> > smc_create_clcsk |
> > sock_create_kern |
> >
> > With CONFIG_DEBUG_LOCK_ALLOC=y, the smc->clcsock is unexpectedly changed
> > in inet_init_csk_locks(). The INET_PROTOSW_ICSK flag is no need by smc,
> > just remove it.
> >
> > After removing the INET_PROTOSW_ICSK flag, this patch alse revert
> > commit 6fd27ea183c2 ("net/smc: fix lacks of icsk_syn_mss with IPPROTO_SMC")
> > to avoid casting smc_sock to inet_connection_sock.
> >
> > Reported-by: syzbot+f775be4458668f7d220e@syzkaller.appspotmail.com
> > Closes: https://syzkaller.appspot.com/bug?extid=f775be4458668f7d220e
> > Tested-by: syzbot+f775be4458668f7d220e@syzkaller.appspotmail.com
>
> nit: looks like this diff is not tested by syzbot, you may
> want to send diff to syzbot.
>
>
> > Fixes: d25a92ccae6b ("net/smc: Introduce IPPROTO_SMC")
> > Signed-off-by: Wang Liang <wangliang74@huawei.com>
>
> Change itself looks good.
>
> Reviewed-by: Kuniyuki Iwashima <kuniyu@google.com>

Agreed

Reviewed-by: Eric Dumazet <edumazet@google.com>