syzbot reported a NULL dereference caused by a missing check
in hwsim_pmsr_report_nl(), and bisected the issue to cited commit.

v2: test the nlattr before using nla_data() on it (Simon Horman)

general protection fault, probably for non-canonical address 0xdffffc0000000001: 0000 [#1] PREEMPT SMP KASAN
KASAN: null-ptr-deref in range [0x0000000000000008-0x000000000000000f]
CPU: 0 PID: 5084 Comm: syz-executor104 Not tainted 6.3.0-rc4-next-20230331-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/02/2023
RIP: 0010:jhash+0x339/0x610 include/linux/jhash.h:95
Code: 83 fd 01 0f 84 5f ff ff ff eb de 83 fd 05 74 3a e8 ac f5 71 fd 48 8d 7b 05 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <0f> b6 04 02 48 89 fa 83 e2 07 38 d0 7f 08 84 c0 0f 85 96 02 00 00
RSP: 0018:ffffc90003abf298 EFLAGS: 00010202
RAX: dffffc0000000000 RBX: 0000000000000004 RCX: 0000000000000000
RDX: 0000000000000001 RSI: ffffffff84111ba4 RDI: 0000000000000009
RBP: 0000000000000006 R08: 0000000000000005 R09: 000000000000000c
R10: 0000000000000006 R11: 0000000000000000 R12: 000000004d2c27cd
R13: 000000002bd9e6c2 R14: 000000002bd9e6c2 R15: 000000002bd9e6c2
FS: 0000555556847300(0000) GS:ffff8880b9800000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000000045ad50 CR3: 0000000078aa6000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
rht_key_hashfn include/linux/rhashtable.h:159 [inline]
__rhashtable_lookup include/linux/rhashtable.h:604 [inline]
rhashtable_lookup include/linux/rhashtable.h:646 [inline]
rhashtable_lookup_fast include/linux/rhashtable.h:672 [inline]
get_hwsim_data_ref_from_addr+0xb9/0x600 drivers/net/wireless/virtual/mac80211_hwsim.c:757
hwsim_pmsr_report_nl+0xe7/0xd50 drivers/net/wireless/virtual/mac80211_hwsim.c:3764
genl_family_rcv_msg_doit.isra.0+0x1e6/0x2d0 net/netlink/genetlink.c:968
genl_family_rcv_msg net/netlink/genetlink.c:1048 [inline]
genl_rcv_msg+0x4ff/0x7e0 net/netlink/genetlink.c:1065
netlink_rcv_skb+0x165/0x440 net/netlink/af_netlink.c:2572
genl_rcv+0x28/0x40 net/netlink/genetlink.c:1076
netlink_unicast_kernel net/netlink/af_netlink.c:1339 [inline]
netlink_unicast+0x547/0x7f0 net/netlink/af_netlink.c:1365
netlink_sendmsg+0x925/0xe30 net/netlink/af_netlink.c:1942
sock_sendmsg_nosec net/socket.c:724 [inline]
sock_sendmsg+0xde/0x190 net/socket.c:747
____sys_sendmsg+0x71c/0x900 net/socket.c:2501
___sys_sendmsg+0x110/0x1b0 net/socket.c:2555
__sys_sendmsg+0xf7/0x1c0 net/socket.c:2584
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd

Fixes: 2af3b2a6 ("mac80211_hwsim: add PMSR report support via virtio")
Reported-by: syzbot <syzkaller@googlegroups.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Jaewan Kim <jaewan@google.com>
Cc: Johannes Berg <johannes.berg@intel.com>
Reviewed-by: Simon Horman <simon.horman@corigine.com>
Reviewed-by: Jaewan Kim <jaewan@google.com>
Link: https://lore.kernel.org/r/20230404171658.917361-1-edumazet@google.comSigned-off-by: Johannes Berg <johannes.berg@intel.com>