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

D. Wythe
2025-10-17T09:03:30Z

On Fri, Oct 17, 2025 at 10:48:27AM +0800, Wang Liang wrote:
> 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
> Fixes: d25a92ccae6b ("net/smc: Introduce IPPROTO_SMC")
> Signed-off-by: Wang Liang <wangliang74@huawei.com>
> ---
> v2: remove INET_PROTOSW_ICSK flag instead of init inet_connection_sock.
> v1: https://lore.kernel.org/netdev/20250922121818.654011-1-wangliang74@huawei.com/
> ---

LGTM.

Reviewed-by: D. Wythe <alibuda@linux.alibaba.com>