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

[Wang Liang <wangliang74@huawei.com>]

在 2025/10/17 13:48, Kuniyuki Iwashima 写道:
> 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.
>

Thank you for the reminder!

I just sent this diff to syzbot, and the test return OK:
https://lore.kernel.org/netdev/b76f348d-61d3-404b-81c6-57621a14046b@huawei.com/T/#t

------
Best regards
Wang Liang

>> 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>
>
> Thanks!