bnx2fc: fix tgt spinlock locking

bnx2fc_queuecommand(): when allocating a new io_req, the tgt_lock
spinlock must be locked before calling bnx2fc_cmd_alloc().

The spinlock should also be kept locked until bnx2fc_post_io_req() has
been completed.
If not, a kernel thread may call bnx2fc_process_cq_compl() that extracts
the newly allocated io_req from hba->cmd_mgr->cmds and destroys it while
it is still being used by bnx2fc_post_io_req().

BUG: unable to handle kernel NULL pointer dereference at 000000000000004c
IP: [<ffffffffa03130da>] bnx2fc_init_task+0x6a/0x230 [bnx2fc]
PGD 0
Oops: 0000 [#1] SMP
last sysfs file: /sys/devices/pci0000:00/0000:00:02.0/0000:04:00.3/net/eth3/type
CPU 33
Modules linked in: autofs4 target_core_iblock target_core_file target_core_pscsi target_core_mod configfs bnx2fc cnic uio fcoe libfcoe libfc scsi_transport_fc 8021q garp scsi_tgt stp llc cpufreq_ondemand freq_table pcc_cpufreq ipt_REJECT nf_conntrack_ipv4 nf_defrag_ipv4 iptable_filter ip_tables ip6t_REJECT nf_conntrack_ipv6 nf_defrag_ipv6 xt_state nf_conntrack ip6table_filter ip6_tables ipv6 power_meter microcode iTCO_wdt iTCO_vendor_support hpilo hpwdt sg bnx2x libcrc32c mdio serio_raw lpc_ich mfd_core shpchp ext4 jbd2 mbcache sd_mod crc_t10dif hpsa video output dm_mirror dm_region_hash dm_log dm_mod [last unloaded: scsi_wait_scan]

Pid: 7355, comm: bnx2fc_thread/3 Not tainted 2.6.32-431.el6.x86_64 #1 HP ProLiant BL460c Gen8
RIP: 0010:[<ffffffffa03130da>]  [<ffffffffa03130da>] bnx2fc_init_task+0x6a/0x230 [bnx2fc]
RSP: 0018:ffff8820b0da3b68  EFLAGS: 00010246
RAX: 0000000000000000 RBX: ffff882003801080 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff882003801100
RBP: ffff8820b0da3bc8 R08: ffffffff8160d4e8 R09: 0000000000000040
R10: 0000000000000000 R11: 0000000000000000 R12: ffff88400e600e00
R13: ffff8840108fbe40 R14: ffff88200ffe5400 R15: 0000000000000000
FS:  0000000000000000(0000) GS:ffff8820b0da0000(0000) knlGS:0000000000000000
CS:  0010 DS: 0018 ES: 0018 CR0: 000000008005003b
CR2: 000000000000004c CR3: 0000002010b67000 CR4: 00000000001407e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
Process bnx2fc_thread/3 (pid: 7355, threadinfo ffff88401f940000, task ffff884012f5f540)
Stack:
 ffff8820b0da3bc8 ffffffff81527303 ffff884000000020 ffff8820b0da3bd8
<d> ffff8820b0da3b98 000000028138931a ffff88400f506078 ffff88400e600e00
<d> ffff88200ffe5400 ffff88200ffe5590 0000000000000021 0000000000000002
Call Trace:
 <IRQ>
 [<ffffffff81527303>] ? printk+0x41/0x46
 [<ffffffffa03169bc>] bnx2fc_post_io_req+0x11c/0x440 [bnx2fc]
 [<ffffffff812825b9>] ? cpumask_next_and+0x29/0x50
 [<ffffffff8137ffd0>] ? scsi_done+0x0/0x60
 [<ffffffffa0316df7>] bnx2fc_queuecommand+0x117/0x140 [bnx2fc]
 [<ffffffff81380245>] scsi_dispatch_cmd+0xe5/0x310
 [<ffffffff81388b9e>] scsi_request_fn+0x5ee/0x7a0
 [<ffffffff812658f1>] __blk_run_queue+0x31/0x40
 [<ffffffff81265a40>] blk_run_queue+0x30/0x50
 [<ffffffff81387da6>] scsi_run_queue+0xc6/0x270
 [<ffffffff81260f92>] ? elv_requeue_request+0x52/0xa0
 [<ffffffff813897a0>] scsi_requeue_command+0x90/0xb0
 [<ffffffff81389b84>] scsi_io_completion+0x154/0x6c0
 [<ffffffff8137ff62>] scsi_finish_command+0xc2/0x130
 [<ffffffff8138a255>] scsi_softirq_done+0x145/0x170
 [<ffffffff8126e865>] blk_done_softirq+0x85/0xa0
 [<ffffffff8107a8e1>] __do_softirq+0xc1/0x1e0
 [<ffffffff8100c30c>] ? call_softirq+0x1c/0x30
 [<ffffffff8100c30c>] call_softirq+0x1c/0x30
 <EOI>
 [<ffffffff8100fa75>] ? do_softirq+0x65/0xa0
 [<ffffffff8107a40a>] local_bh_enable_ip+0x9a/0xb0
 [<ffffffff8152a4eb>] _spin_unlock_bh+0x1b/0x20
 [<ffffffffa0313937>] bnx2fc_process_cq_compl+0x257/0x2b0 [bnx2fc]
 [<ffffffffa03114ea>] bnx2fc_percpu_io_thread+0xea/0x160 [bnx2fc]
 [<ffffffffa0311400>] ? bnx2fc_percpu_io_thread+0x0/0x160 [bnx2fc]
 [<ffffffff8109aef6>] kthread+0x96/0xa0
 [<ffffffff8100c20a>] child_rip+0xa/0x20
 [<ffffffff8109ae60>] ? kthread+0x0/0xa0
 [<ffffffff8100c200>] ? child_rip+0x0/0x20
Code: 89 df 45 8b 7e 30 0f 85 75 01 00 00 89 d1 31 c0 c1 e9 03 83 e2 04 89 c9 f3 48 ab 74 06 c7 07 00 00 00 00 49 89 9c 24 88 01 00 00 <83> 7e 4c 01 b8 01 00 00 00 0f 84 e7 00 00 00 89 c2 0a 53 38 41
RIP  [<ffffffffa03130da>] bnx2fc_init_task+0x6a/0x230 [bnx2fc]
 RSP <ffff8820b0da3b68>
CR2: 000000000000004c
Signed-off-by: Maurizio Lombardi <mlombard@redhat.com>
Acked-by: Chad Dupuis <chad.dupuis@qlogic.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>

drivers/scsi/bnx2fc/bnx2fc_els.c

@@ -480,9 +480,7 @@ void bnx2fc_rec_compl(struct bnx2fc_els_cb_arg *cb_arg)
 			bnx2fc_initiate_cleanup(orig_io_req);
 			/* Post a new IO req with the same sc_cmd */
 			BNX2FC_IO_DBG(rec_req, "Post IO request again\n");
-			spin_unlock_bh(&tgt->tgt_lock);
 			rc = bnx2fc_post_io_req(tgt, new_io_req);
-			spin_lock_bh(&tgt->tgt_lock);
 			if (!rc)
 				goto free_frame;
 			BNX2FC_IO_DBG(rec_req, "REC: io post err\n");

drivers/scsi/bnx2fc/bnx2fc_io.c

@@ -1894,18 +1894,24 @@ int bnx2fc_queuecommand(struct Scsi_Host *host,
 			goto exit_qcmd;
 		}
 	}
+
+	spin_lock_bh(&tgt->tgt_lock);
+
 	io_req = bnx2fc_cmd_alloc(tgt);
 	if (!io_req) {
 		rc = SCSI_MLQUEUE_HOST_BUSY;
-		goto exit_qcmd;
+		goto exit_qcmd_tgtlock;
 	}
 	io_req->sc_cmd = sc_cmd;
 
 	if (bnx2fc_post_io_req(tgt, io_req)) {
 		printk(KERN_ERR PFX "Unable to post io_req\n");
 		rc = SCSI_MLQUEUE_HOST_BUSY;
-		goto exit_qcmd;
+		goto exit_qcmd_tgtlock;
 	}
+
+exit_qcmd_tgtlock:
+	spin_unlock_bh(&tgt->tgt_lock);
 exit_qcmd:
 	return rc;
 }
@@ -2020,6 +2026,8 @@ int bnx2fc_post_io_req(struct bnx2fc_rport *tgt,
 	int task_idx, index;
 	u16 xid;
 
+	/* bnx2fc_post_io_req() is called with the tgt_lock held */
+
 	/* Initialize rest of io_req fields */
 	io_req->cmd_type = BNX2FC_SCSI_CMD;
 	io_req->port = port;
@@ -2047,9 +2055,7 @@ int bnx2fc_post_io_req(struct bnx2fc_rport *tgt,
 	/* Build buffer descriptor list for firmware from sg list */
 	if (bnx2fc_build_bd_list_from_sg(io_req)) {
 		printk(KERN_ERR PFX "BD list creation failed\n");
-		spin_lock_bh(&tgt->tgt_lock);
 		kref_put(&io_req->refcount, bnx2fc_cmd_release);
-		spin_unlock_bh(&tgt->tgt_lock);
 		return -EAGAIN;
 	}
 
@@ -2061,19 +2067,15 @@ int bnx2fc_post_io_req(struct bnx2fc_rport *tgt,
 	task = &(task_page[index]);
 	bnx2fc_init_task(io_req, task);
 
-	spin_lock_bh(&tgt->tgt_lock);
-
 	if (tgt->flush_in_prog) {
 		printk(KERN_ERR PFX "Flush in progress..Host Busy\n");
 		kref_put(&io_req->refcount, bnx2fc_cmd_release);
-		spin_unlock_bh(&tgt->tgt_lock);
 		return -EAGAIN;
 	}
 
 	if (!test_bit(BNX2FC_FLAG_SESSION_READY, &tgt->flags)) {
 		printk(KERN_ERR PFX "Session not ready...post_io\n");
 		kref_put(&io_req->refcount, bnx2fc_cmd_release);
-		spin_unlock_bh(&tgt->tgt_lock);
 		return -EAGAIN;
 	}
 
@@ -2091,6 +2093,5 @@ int bnx2fc_post_io_req(struct bnx2fc_rport *tgt,
 
 	/* Ring doorbell */
 	bnx2fc_ring_doorbell(tgt);
-	spin_unlock_bh(&tgt->tgt_lock);
 	return 0;
 }