scsi: libiscsi: Validate the task named by a management response

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

scsi: libiscsi: Validate the task named by a management response

__iscsi_complete_pdu() fetches the task for five response types from one
place and checks only that the index resolved:

case ISCSI_OP_LOGOUT_RSP:
case ISCSI_OP_LOGIN_RSP:
case ISCSI_OP_TEXT_RSP:
case ISCSI_OP_SCSI_TMFUNC_RSP:
case ISCSI_OP_NOOP_IN:
task = iscsi_itt_to_task(conn, hdr->itt);
if (!task)
return ISCSI_ERR_BAD_ITT;

iscsi_itt_to_task() bounds the index against cmds_max and looks at
nothing else, so a target can name any slot in the pool, including one
that has never been used. task->conn is then NULL, and both
iscsi_nop_out_rsp() and iscsi_complete_task() dereference it. One
unsolicited NOP-In is enough; a Text Response carrying the same ITT
crashes in iscsi_complete_task() instead.

Require the task to be in flight and not a SCSI command, the way
iscsi_itt_to_ctask() does for the command opcodes.

[ 6.298634] Oops: general protection fault, probably for non-canonical address 0xdffffc000000000c: 0000 [#1] SMP KASAN NOPTI
[ 6.298642] KASAN: null-ptr-deref in range [0x0000000000000060-0x0000000000000067]
[ 6.298652] CPU: 1 UID: 0 PID: 111 Comm: iscsistart Not tainted 7.2.0-rc5-ISCSI1-gf5098b6bae76 #1 PREEMPT(lazy)
[ 6.298654] Hardware name: QEMU Ubuntu 24.04 PC v2 (i440FX + PIIX, arch_caps fix, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
[ 6.298656] RIP: 0010:iscsi_nop_out_rsp.constprop.0+0x46/0x160
[ 6.298691] Code: c1 ea 03 48 83 ec 08 80 3c 02 00 0f 85 f5 00 00 00 48 b8 00 00 00 00 00 fc ff df 48 8b 6b 58 48 8d 7d 60 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 c0 00 00 00 48 8b 45 60 48 39 c3 74 50 48 b8 00
[ 6.298698] RSP: 0018:ffff88806c907be8 EFLAGS: 00010206
[ 6.298701] RAX: dffffc0000000000 RBX: ffff888006116800 RCX: 0000000000000020
[ 6.298702] RDX: 000000000000000c RSI: ffff88800525d578 RDI: 0000000000000060
[ 6.298703] RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
[ 6.298706] R10: 0000000000000020 R11: 0000000000000000 R12: 0000000000000000
[ 6.298706] R13: 000000000000002e R14: ffff8880056eb440 R15: ffff888006116800
[ 6.298707] FS: 00007fc02d1c2740(0000) GS:ffff8880b29bc000(0000) knlGS:0000000000000000
[ 6.298710] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 6.298711] CR2: 000055fe3b56ddf8 CR3: 00000000053b9004 CR4: 0000000000770ef0
[ 6.298712] PKRU: 55555554
[ 6.298713] Call Trace:
[ 6.298714] <IRQ>
[ 6.298714] __iscsi_complete_pdu+0x13a8/0x22a0
[ 6.298758] iscsi_complete_pdu+0x54/0xa0
[ 6.298759] iscsi_tcp_hdr_recv_done+0x870/0x2c80
[ 6.298778] iscsi_tcp_recv_skb+0x31e/0xec0
[ 6.298800] iscsi_sw_tcp_recv+0x12f/0x390
[ 6.298804] __tcp_read_sock+0x1ab/0x810
[ 6.298812] iscsi_sw_tcp_data_ready+0x18b/0x510
[ 6.298814] tcp_rcv_established+0x1f56/0x3a00
[ 6.298842] tcp_v4_do_rcv+0x449/0x960
[ 6.298847] tcp_v4_rcv+0x2245/0x3bc0