rds: fixed kernel oops in case of error flow

rds: fixed kernel oops in case of error flow

If failed to create an rdma_cm handler, don't try to free it and
prevent the following kernel oops:

BUG: unable to handle kernel NULL pointer dereference at 00000000000001fc
IP: [<ffffffff814ef21f>] _spin_lock_irqsave+0x1f/0x40
PGD 175b80067 PUD 176a0b067 PMD 0
Oops: 0002 [#1] SMP
last sysfs file: /sys/module/rds/initstate
CPU 0
Modules linked in: rds_rdma(+)(U) rds(U) ib_ucm(U) rdma_cm(U) iw_cm(U) ib_addr(U) ib_srp(U) scsi_transport_srp scsi_tgt ib_ipoib(U) ib_cm(U) ib_sa(U) ib_uverbs(U) ib_umad(U) mlx4_ib(U) ib_mad(U) ib_core(U) mlx4_core(U) memtrack(U) netconsole configfs nfs fscache nfsd lockd nfs_acl auth_rpcgss exportfs autofs4 sunrpc ipv6 microcode virtio_balloon virtio_net snd_hda_intel snd_hda_codec snd_hwdep snd_seq snd_seq_device snd_pcm snd_timer snd soundcore snd_page_alloc i2c_piix4 i2c_core ext3 jbd mbcache virtio_blk pata_acpi ata_generic ata_piix virtio_pci virtio_ring virtio dm_mirror dm_region_hash dm_log dm_mod [last unloaded: memtrack]

Pid: 22908, comm: modprobe Not tainted 2.6.32-220.el6.x86_64 #1 Red Hat KVM
RIP: 0010:[<ffffffff814ef21f>]  [<ffffffff814ef21f>] _spin_lock_irqsave+0x1f/0x40
RSP: 0018:ffff880125f07e68  EFLAGS: 00010086
RAX: 0000000000010000 RBX: fffffffffffffff4 RCX: 0000000000000000
RDX: 0000000000000286 RSI: 000000000000000a RDI: 00000000000001fc
RBP: ffff880125f07e68 R08: 0000000000000000 R09: ffff880176db4020
R10: ffff880125f07988 R11: 0000000000000002 R12: 00000000000001fc
R13: 0000000000d8e4c0 R14: 000000000000000a R15: 0000000000000000
FS:  00007f66c90cc700(0000) GS:ffff880028200000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
CR2: 00000000000001fc CR3: 000000011e71b000 CR4: 00000000000006f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
Process modprobe (pid: 22908, threadinfo ffff880125f06000, task ffff880174732b40)
Stack:
 ffff880125f07e98 ffffffffa03dd795 fffffffffffffff4 fffffffffffffff4
<0> 0000000000d8e4c0 0000000000000000 ffff880125f07ed8 ffffffffa03dee11
<0> ffff880125f07ee8 00000000fffffff4 00000000fffffff4 fffffffffffffff4
Call Trace:
 [<ffffffffa03dd795>] cma_exch+0x35/0x70 [rdma_cm]
 [<ffffffffa03dee11>] rdma_destroy_id+0x21/0x310 [rdma_cm]
 [<ffffffffa042a0be>] init_module+0xbe/0x118 [rds_rdma]
 [<ffffffff81096e75>] ? __blocking_notifier_call_chain+0x65/0x80
 [<ffffffffa042a000>] ? init_module+0x0/0x118 [rds_rdma]
 [<ffffffff8100204c>] do_one_initcall+0x3c/0x1d0
 [<ffffffff810af641>] sys_init_module+0xe1/0x250
 [<ffffffff8100b0f2>] system_call_fastpath+0x16/0x1b
Code: c9 c3 66 2e 0f 1f 84 00 00 00 00 00 55 48 89 e5 0f 1f 44 00 00 9c 58 0f 1f 44 00 00 48 89 c2 fa 66 0f 1f 44 00 00 b8 00 00 01 00 <f0> 0f c1 07 0f b7 c8 c1 e8 10 39 c1 74 0e f3 90 0f 1f 44 00 00
RIP  [<ffffffff814ef21f>] _spin_lock_irqsave+0x1f/0x40
 RSP <ffff880125f07e68>
CR2: 00000000000001fc
---[ end trace 8db2f942777f29d0 ]---

Signed-off-by: Dotan Barak <dotanb@dev.mellanox.co.il>