net/smc: fix lacks of icsk_syn_mss with IPPROTO_SMC

In the Linux kernel, the following vulnerability has been resolved:

net/smc: fix lacks of icsk_syn_mss with IPPROTO_SMC

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.