netdev - Re: [PATCH net] net/smc: fix lacks of icsk_syn_mss with IPPROTO

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Message-ID: <0687fd39-7fa9-416c-be91-d33a2432c71a@linux.ibm.com>
Date: Wed, 9 Oct 2024 16:57:04 +0200
From: Wenjia Zhang <wenjia@...ux.ibm.com>
To: "D. Wythe" <alibuda@...ux.alibaba.com>, kgraul@...ux.ibm.com,
        jaka@...ux.ibm.com, wintera@...ux.ibm.com, guwen@...ux.alibaba.com
Cc: kuba@...nel.org, davem@...emloft.net, netdev@...r.kernel.org,
        linux-s390@...r.kernel.org, linux-rdma@...r.kernel.org,
        tonylu@...ux.alibaba.com, pabeni@...hat.com, edumazet@...gle.com
Subject: Re: [PATCH net] net/smc: fix lacks of icsk_syn_mss with IPPROTO_SMC



On 09.10.24 08:55, D. Wythe wrote:
> From: "D. Wythe" <alibuda@...ux.alibaba.com>
> 
> Eric report a panic on IPPROTO_SMC, and give the facts
> that when INET_PROTOSW_ICSK was set, icsk->icsk_sync_mss must be set too.
> 
> Bug: Unable to handle kernel NULL pointer dereference at virtual address
> 0000000000000000
> Mem abort info:
> ESR = 0x0000000086000005
> EC = 0x21: IABT (current EL), IL = 32 bits
> SET = 0, FnV = 0
> EA = 0, S1PTW = 0
> FSC = 0x05: level 1 translation fault
> user pgtable: 4k pages, 48-bit VAs, pgdp=00000001195d1000
> [0000000000000000] pgd=0800000109c46003, p4d=0800000109c46003,
> pud=0000000000000000
> Internal error: Oops: 0000000086000005 [#1] PREEMPT SMP
> Modules linked in:
> CPU: 1 UID: 0 PID: 8037 Comm: syz.3.265 Not tainted
> 6.11.0-rc7-syzkaller-g5f5673607153 #0
> Hardware name: Google Google Compute Engine/Google Compute Engine,
> BIOS Google 08/06/2024
> pstate: 80400005 (Nzcv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
> pc : 0x0
> lr : cipso_v4_sock_setattr+0x2a8/0x3c0 net/ipv4/cipso_ipv4.c:1910
> sp : ffff80009b887a90
> x29: ffff80009b887aa0 x28: ffff80008db94050 x27: 0000000000000000
> x26: 1fffe0001aa6f5b3 x25: dfff800000000000 x24: ffff0000db75da00
> x23: 0000000000000000 x22: ffff0000d8b78518 x21: 0000000000000000
> x20: ffff0000d537ad80 x19: ffff0000d8b78000 x18: 1fffe000366d79ee
> x17: ffff8000800614a8 x16: ffff800080569b84 x15: 0000000000000001
> x14: 000000008b336894 x13: 00000000cd96feaa x12: 0000000000000003
> x11: 0000000000040000 x10: 00000000000020a3 x9 : 1fffe0001b16f0f1
> x8 : 0000000000000000 x7 : 0000000000000000 x6 : 000000000000003f
> x5 : 0000000000000040 x4 : 0000000000000001 x3 : 0000000000000000
> x2 : 0000000000000002 x1 : 0000000000000000 x0 : ffff0000d8b78000
> Call trace:
> 0x0
> netlbl_sock_setattr+0x2e4/0x338 net/netlabel/netlabel_kapi.c:1000
> smack_netlbl_add+0xa4/0x154 security/smack/smack_lsm.c:2593
> smack_socket_post_create+0xa8/0x14c security/smack/smack_lsm.c:2973
> security_socket_post_create+0x94/0xd4 security/security.c:4425
> __sock_create+0x4c8/0x884 net/socket.c:1587
> sock_create net/socket.c:1622 [inline]
> __sys_socket_create net/socket.c:1659 [inline]
> __sys_socket+0x134/0x340 net/socket.c:1706
> __do_sys_socket net/socket.c:1720 [inline]
> __se_sys_socket net/socket.c:1718 [inline]
> __arm64_sys_socket+0x7c/0x94 net/socket.c:1718
> __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline]
> invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:49
> el0_svc_common+0x130/0x23c arch/arm64/kernel/syscall.c:132
> do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:151
> el0_svc+0x54/0x168 arch/arm64/kernel/entry-common.c:712
> el0t_64_sync_handler+0x84/0xfc arch/arm64/kernel/entry-common.c:730
> el0t_64_sync+0x190/0x194 arch/arm64/kernel/entry.S:598
> Code: ???????? ???????? ???????? ???????? (????????)
> ---[ end trace 0000000000000000 ]---
> 
> This patch add a toy implementation that performs a simple return to
> prevent such panic. This is because MSS can be set in sock_create_kern
> or smc_setsockopt, similar to how it's done in AF_SMC. However, for
> AF_SMC, there is currently no way to synchronize MSS within
> __sys_connect_file. This toy implementation lays the groundwork for us
> to support such feature for IPPROTO_SMC in the future.
> 
> Fixes: d25a92ccae6b ("net/smc: Introduce IPPROTO_SMC")
> Reported-by: Eric Dumazet <edumazet@...gle.com>
> Signed-off-by: D. Wythe <alibuda@...ux.alibaba.com>
> ---

It looks good to me! Thank you for fixing it!

Reviewed-by: Wenjia Zhang <wenjia@...ux.ibm.com>

Thanks,
Wenjia