spdk: defensive rpc_nvmf_get_qpairs

[baum]

spdk: defensive rpc_nvmf_get_qpairs

crash

Program terminated with signal SIGSEGV, Segmentation fault.
#0  rpc_nvmf_get_qpairs (i=0x218f230) at nvmf_rpc.c:2642
2642    nvmf_rpc.c: Directory not empty.
[Current thread is 1 (Thread 0x7f9eb6bc2780 (LWP 122))]
Missing separate debuginfos, use: dnf debuginfo-install thrift-0.15.0-2.el9.x86_64
(gdb)
(gdb)
(gdb) c
The program is not being run.
(gdb) bt
#0  rpc_nvmf_get_qpairs (i=0x218f230) at nvmf_rpc.c:2642
#1  0x00000000005c0572 in _call_channel (ctx=0x218f230) at thread.c:2552
#2  0x00000000005bc3cc in msg_queue_run_batch (thread=0x1ca2e80, max_msgs=8) at thread.c:848
#3  0x00000000005bcd6b in thread_poll (thread=0x1ca2e80, max_msgs=0, now=31713605381769668) at thread.c:1070
#4  0x00000000005bd077 in spdk_thread_poll (thread=0x1ca2e80, max_msgs=0, now=31713605381769668) at thread.c:1163
#5  0x000000000057a0b9 in _reactor_run (reactor=0x1c55e40) at reactor.c:914
#6  0x000000000057a1ad in reactor_run (arg=0x1c55e40) at reactor.c:952
#7  0x000000000057a652 in spdk_reactors_start () at reactor.c:1068
#8  0x0000000000576510 in spdk_app_start (opts_user=0x7fff569b9f50, start_fn=0x40992f <nvmf_tgt_started>, arg1=0x0) at app.c:839
#9  0x0000000000409a49 in main (argc=4, argv=0x7fff569ba158) at nvmf_main.c:47
(gdb) f 0
#0  rpc_nvmf_get_qpairs (i=0x218f230) at nvmf_rpc.c:2642
2642    in nvmf_rpc.c
(gdb) info locals
ctx = 0x2318930
ch = 0x1c4eb10
group = 0x1c4eb70
qpair = 0x23bed10
(gdb) p qpair->ctrlr->subsys
Cannot access memory at address 0xe8
(gdb) p qpair->ctrlr
$1 = (struct spdk_nvmf_ctrlr *) 0x0
(gdb)

[gbregman]

The "if (group)" is redundant. If "ch" is not null we can't get a NULL "group". There is a test in the code for a NULL "ch" and we assert if it is. But we probably compile the code with NDEBUG, so the assert does nothing. Anyway, I think we should also display an error message in case "ch" is NULL. This shouldn't happen unless something is wrong.

[gbregman]

I suggest adding:

if (ch)
{
.
.
.
}
else
{
    SPDK_ERRLOG("ch is NULL");
}