net/handshake: fix null-ptr-deref in handshake_nl_done_doit()

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

net/handshake: fix null-ptr-deref in handshake_nl_done_doit()

We should not call trace_handshake_cmd_done_err() if socket lookup has failed.

Also we should call trace_handshake_cmd_done_err() before releasing the file,

otherwise dereferencing sock->sk can return garbage.

This also reverts 7afc6d0a107f ("net/handshake: Fix uninitialized local variable")

Unable to handle kernel paging request at virtual address dfff800000000003

KASAN: null-ptr-deref in range [0x0000000000000018-0x000000000000001f]

Mem abort info:

ESR = 0x0000000096000005

EC = 0x25: DABT (current EL), IL = 32 bits

SET = 0, FnV = 0

EA = 0, S1PTW = 0

FSC = 0x05: level 1 translation fault

Data abort info:

ISV = 0, ISS = 0x00000005, ISS2 = 0x00000000

CM = 0, WnR = 0, TnD = 0, TagAccess = 0

GCS = 0, Overlay = 0, DirtyBit = 0, Xs = 0

[dfff800000000003] address between user and kernel address ranges

Internal error: Oops: 0000000096000005 [#1] PREEMPT SMP

Modules linked in:

CPU: 1 PID: 5986 Comm: syz-executor292 Not tainted 6.5.0-rc7-syzkaller-gfe4469582053 #0

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/26/2023

pstate: 80400005 (Nzcv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)

pc : handshake_nl_done_doit+0x198/0x9c8 net/handshake/netlink.c:193

lr : handshake_nl_done_doit+0x180/0x9c8

sp : ffff800096e37180

x29: ffff800096e37200 x28: 1ffff00012dc6e34 x27: dfff800000000000

x26: ffff800096e373d0 x25: 0000000000000000 x24: 00000000ffffffa8

x23: ffff800096e373f0 x22: 1ffff00012dc6e38 x21: 0000000000000000

x20: ffff800096e371c0 x19: 0000000000000018 x18: 0000000000000000

x17: 0000000000000000 x16: ffff800080516cc4 x15: 0000000000000001

x14: 1fffe0001b14aa3b x13: 0000000000000000 x12: 0000000000000000

x11: 0000000000000000 x10: 0000000000000000 x9 : 0000000000000003

x8 : 0000000000000003 x7 : ffff800080afe47c x6 : 0000000000000000

x5 : 0000000000000000 x4 : 0000000000000000 x3 : ffff800080a88078

x2 : 0000000000000001 x1 : 00000000ffffffa8 x0 : 0000000000000000

Call trace:

handshake_nl_done_doit+0x198/0x9c8 net/handshake/netlink.c:193

genl_family_rcv_msg_doit net/netlink/genetlink.c:970 [inline]

genl_family_rcv_msg net/netlink/genetlink.c:1050 [inline]

genl_rcv_msg+0x96c/0xc50 net/netlink/genetlink.c:1067

netlink_rcv_skb+0x214/0x3c4 net/netlink/af_netlink.c:2549

genl_rcv+0x38/0x50 net/netlink/genetlink.c:1078

netlink_unicast_kernel net/netlink/af_netlink.c:1339 [inline]

netlink_unicast+0x660/0x8d4 net/netlink/af_netlink.c:1365

netlink_sendmsg+0x834/0xb18 net/netlink/af_netlink.c:1914

sock_sendmsg_nosec net/socket.c:725 [inline]

sock_sendmsg net/socket.c:748 [inline]

____sys_sendmsg+0x56c/0x840 net/socket.c:2494

___sys_sendmsg net/socket.c:2548 [inline]

__sys_sendmsg+0x26c/0x33c net/socket.c:2577

__do_sys_sendmsg net/socket.c:2586 [inline]

__se_sys_sendmsg net/socket.c:2584 [inline]

__arm64_sys_sendmsg+0x80/0x94 net/socket.c:2584

__invoke_syscall arch/arm64/kernel/syscall.c:37 [inline]

invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:51

el0_svc_common+0x130/0x23c arch/arm64/kernel/syscall.c:136

do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:155

el0_svc+0x58/0x16c arch/arm64/kernel/entry-common.c:678

el0t_64_sync_handler+0x84/0xfc arch/arm64/kernel/entry-common.c:696

el0t_64_sync+0x190/0x194 arch/arm64/kernel/entry.S:591

Code: 12800108 b90043e8 910062b3 d343fe68 (387b6908)