We used to use the wrong type of integer in 'zfcp_fsf_req_send()' to cache
the FSF request ID when sending a new FSF request. This is used in case the
sending fails and we need to remove the request from our internal hash
table again (so we don't keep an invalid reference and use it when we free
the request again).

In 'zfcp_fsf_req_send()' we used to cache the ID as 'int' (signed and 32
bit wide), but the rest of the zfcp code (and the firmware specification)
handles the ID as 'unsigned long'/'u64' (unsigned and 64 bit wide [s390x
ELF ABI]).  For one this has the obvious problem that when the ID grows
past 32 bit (this can happen reasonably fast) it is truncated to 32 bit
when storing it in the cache variable and so doesn't match the original ID
anymore.  The second less obvious problem is that even when the original ID
has not yet grown past 32 bit, as soon as the 32nd bit is set in the
original ID (0x80000000 = 2'147'483'648) we will have a mismatch when we
cast it back to 'unsigned long'. As the cached variable is of a signed
type, the compiler will choose a sign-extending instruction to load the 32
bit variable into a 64 bit register (e.g.: 'lgf %r11,188(%r15)'). So once
we pass the cached variable into 'zfcp_reqlist_find_rm()' to remove the
request again all the leading zeros will be flipped to ones to extend the
sign and won't match the original ID anymore (this has been observed in
practice).

If we can't successfully remove the request from the hash table again after
'zfcp_qdio_send()' fails (this happens regularly when zfcp cannot notify
the adapter about new work because the adapter is already gone during
e.g. a ChpID toggle) we will end up with a double free.  We unconditionally
free the request in the calling function when 'zfcp_fsf_req_send()' fails,
but because the request is still in the hash table we end up with a stale
memory reference, and once the zfcp adapter is either reset during recovery
or shutdown we end up freeing the same memory twice.

The resulting stack traces vary depending on the kernel and have no direct
correlation to the place where the bug occurs. Here are three examples that
have been seen in practice:

  list_del corruption. next->prev should be 00000001b9d13800, but was 00000000dead4ead. (next=00000001bd131a00)
  ------------[ cut here ]------------
  kernel BUG at lib/list_debug.c:62!
  monitor event: 0040 ilc:2 [#1] PREEMPT SMP
  Modules linked in: ...
  CPU: 9 PID: 1617 Comm: zfcperp0.0.1740 Kdump: loaded
  Hardware name: ...
  Krnl PSW : 0704d00180000000 00000003cbeea1f8 (__list_del_entry_valid+0x98/0x140)
             R:0 T:1 IO:1 EX:1 Key:0 M:1 W:0 P:0 AS:3 CC:1 PM:0 RI:0 EA:3
  Krnl GPRS: 00000000916d12f1 0000000080000000 000000000000006d 00000003cb665cd6
             0000000000000001 0000000000000000 0000000000000000 00000000d28d21e8
             00000000d3844000 00000380099efd28 00000001bd131a00 00000001b9d13800
             00000000d3290100 0000000000000000 00000003cbeea1f4 00000380099efc70
  Krnl Code: 00000003cbeea1e8: c020004f68a7        larl    %r2,00000003cc8d7336
             00000003cbeea1ee: c0e50027fd65        brasl   %r14,00000003cc3e9cb8
            #00000003cbeea1f4: af000000            mc      0,0
            >00000003cbeea1f8: c02000920440        larl    %r2,00000003cd12aa78
             00000003cbeea1fe: c0e500289c25        brasl   %r14,00000003cc3fda48
             00000003cbeea204: b9040043            lgr     %r4,%r3
             00000003cbeea208: b9040051            lgr     %r5,%r1
             00000003cbeea20c: b9040032            lgr     %r3,%r2
  Call Trace:
   [<00000003cbeea1f8>] __list_del_entry_valid+0x98/0x140
  ([<00000003cbeea1f4>] __list_del_entry_valid+0x94/0x140)
   [<000003ff7ff502fe>] zfcp_fsf_req_dismiss_all+0xde/0x150 [zfcp]
   [<000003ff7ff49cd0>] zfcp_erp_strategy_do_action+0x160/0x280 [zfcp]
   [<000003ff7ff4a22e>] zfcp_erp_strategy+0x21e/0xca0 [zfcp]
   [<000003ff7ff4ad34>] zfcp_erp_thread+0x84/0x1a0 [zfcp]
   [<00000003cb5eece8>] kthread+0x138/0x150
   [<00000003cb557f3c>] __ret_from_fork+0x3c/0x60
   [<00000003cc4172ea>] ret_from_fork+0xa/0x40
  INFO: lockdep is turned off.
  Last Breaking-Event-Address:
   [<00000003cc3e9d04>] _printk+0x4c/0x58
  Kernel panic - not syncing: Fatal exception: panic_on_oops

or:

  Unable to handle kernel pointer dereference in virtual kernel address space
  Failing address: 6b6b6b6b6b6b6000 TEID: 6b6b6b6b6b6b6803
  Fault in home space mode while using kernel ASCE.
  AS:0000000063b10007 R3:0000000000000024
  Oops: 0038 ilc:3 [#1] SMP
  Modules linked in: ...
  CPU: 10 PID: 0 Comm: swapper/10 Kdump: loaded
  Hardware name: ...
  Krnl PSW : 0404d00180000000 000003ff7febaf8e (zfcp_fsf_reqid_check+0x86/0x158 [zfcp])
             R:0 T:1 IO:0 EX:0 Key:0 M:1 W:0 P:0 AS:3 CC:1 PM:0 RI:0 EA:3
  Krnl GPRS: 5a6f1cfa89c49ac3 00000000aff2c4c8 6b6b6b6b6b6b6b6b 00000000000002a8
             0000000000000000 0000000000000055 0000000000000000 00000000a8515800
             0700000000000000 00000000a6e14500 00000000aff2c000 000000008003c44c
             000000008093c700 0000000000000010 00000380009ebba8 00000380009ebb48
  Krnl Code: 000003ff7febaf7e: a7f4003d            brc     15,000003ff7febaff8
             000003ff7febaf82: e32020000004        lg      %r2,0(%r2)
            #000003ff7febaf88: ec2100388064        cgrj    %r2,%r1,8,000003ff7febaff8
            >000003ff7febaf8e: e3b020100020        cg      %r11,16(%r2)
             000003ff7febaf94: a774fff7            brc     7,000003ff7febaf82
             000003ff7febaf98: ec280030007c        cgij    %r2,0,8,000003ff7febaff8
             000003ff7febaf9e: e31020080004        lg      %r1,8(%r2)
             000003ff7febafa4: e33020000004        lg      %r3,0(%r2)
  Call Trace:
   [<000003ff7febaf8e>] zfcp_fsf_reqid_check+0x86/0x158 [zfcp]
   [<000003ff7febbdbc>] zfcp_qdio_int_resp+0x6c/0x170 [zfcp]
   [<000003ff7febbf90>] zfcp_qdio_irq_tasklet+0xd0/0x108 [zfcp]
   [<0000000061d90a04>] tasklet_action_common.constprop.0+0xdc/0x128
   [<000000006292f300>] __do_softirq+0x130/0x3c0
   [<0000000061d906c6>] irq_exit_rcu+0xfe/0x118
   [<000000006291e818>] do_io_irq+0xc8/0x168
   [<000000006292d516>] io_int_handler+0xd6/0x110
   [<000000006292d596>] psw_idle_exit+0x0/0xa
  ([<0000000061d3be50>] arch_cpu_idle+0x40/0xd0)
   [<000000006292ceea>] default_idle_call+0x52/0xf8
   [<0000000061de4fa4>] do_idle+0xd4/0x168
   [<0000000061de51fe>] cpu_startup_entry+0x36/0x40
   [<0000000061d4faac>] smp_start_secondary+0x12c/0x138
   [<000000006292d88e>] restart_int_handler+0x6e/0x90
  Last Breaking-Event-Address:
   [<000003ff7febaf94>] zfcp_fsf_reqid_check+0x8c/0x158 [zfcp]
  Kernel panic - not syncing: Fatal exception in interrupt

or:

  Unable to handle kernel pointer dereference in virtual kernel address space
  Failing address: 523b05d3ae76a000 TEID: 523b05d3ae76a803
  Fault in home space mode while using kernel ASCE.
  AS:0000000077c40007 R3:0000000000000024
  Oops: 0038 ilc:3 [#1] SMP
  Modules linked in: ...
  CPU: 3 PID: 453 Comm: kworker/3:1H Kdump: loaded
  Hardware name: ...
  Workqueue: kblockd blk_mq_run_work_fn
  Krnl PSW : 0404d00180000000 0000000076fc0312 (__kmalloc+0xd2/0x398)
             R:0 T:1 IO:0 EX:0 Key:0 M:1 W:0 P:0 AS:3 CC:1 PM:0 RI:0 EA:3
  Krnl GPRS: ffffffffffffffff 523b05d3ae76abf6 0000000000000000 0000000000092a20
             0000000000000002 00000007e49b5cc0 00000007eda8f000 0000000000092a20
             00000007eda8f000 00000003b02856b9 00000000000000a8 523b05d3ae76abf6
             00000007dd662000 00000007eda8f000 0000000076fc02b2 000003e0037637a0
  Krnl Code: 0000000076fc0302: c004000000d4	brcl	0,76fc04aa
             0000000076fc0308: b904001b		lgr	%r1,%r11
            #0000000076fc030c: e3106020001a	algf	%r1,32(%r6)
            >0000000076fc0312: e31010000082	xg	%r1,0(%r1)
             0000000076fc0318: b9040001		lgr	%r0,%r1
             0000000076fc031c: e30061700082	xg	%r0,368(%r6)
             0000000076fc0322: ec59000100d9	aghik	%r5,%r9,1
             0000000076fc0328: e34003b80004	lg	%r4,952
  Call Trace:
   [<0000000076fc0312>] __kmalloc+0xd2/0x398
   [<0000000076f318f2>] mempool_alloc+0x72/0x1f8
   [<000003ff8027c5f8>] zfcp_fsf_req_create.isra.7+0x40/0x268 [zfcp]
   [<000003ff8027f1bc>] zfcp_fsf_fcp_cmnd+0xac/0x3f0 [zfcp]
   [<000003ff80280f1a>] zfcp_scsi_queuecommand+0x122/0x1d0 [zfcp]
   [<000003ff800b4218>] scsi_queue_rq+0x778/0xa10 [scsi_mod]
   [<00000000771782a0>] __blk_mq_try_issue_directly+0x130/0x208
   [<000000007717a124>] blk_mq_request_issue_directly+0x4c/0xa8
   [<000003ff801302e2>] dm_mq_queue_rq+0x2ea/0x468 [dm_mod]
   [<0000000077178c12>] blk_mq_dispatch_rq_list+0x33a/0x818
   [<000000007717f064>] __blk_mq_do_dispatch_sched+0x284/0x2f0
   [<000000007717f44c>] __blk_mq_sched_dispatch_requests+0x1c4/0x218
   [<000000007717fa7a>] blk_mq_sched_dispatch_requests+0x52/0x90
   [<0000000077176d74>] __blk_mq_run_hw_queue+0x9c/0xc0
   [<0000000076da6d74>] process_one_work+0x274/0x4d0
   [<0000000076da7018>] worker_thread+0x48/0x560
   [<0000000076daef18>] kthread+0x140/0x160
   [<000000007751d144>] ret_from_fork+0x28/0x30
  Last Breaking-Event-Address:
   [<0000000076fc0474>] __kmalloc+0x234/0x398
  Kernel panic - not syncing: Fatal exception: panic_on_oops

To fix this, simply change the type of the cache variable to 'unsigned
long', like the rest of zfcp and also the argument for
'zfcp_reqlist_find_rm()'. This prevents truncation and wrong sign extension
and so can successfully remove the request from the hash table.

Fixes: e60a6d69 ("[SCSI] zfcp: Remove function zfcp_reqlist_find_safe")
Cc: <stable@vger.kernel.org> #v2.6.34+
Signed-off-by: Benjamin Block <bblock@linux.ibm.com>
Link: https://lore.kernel.org/r/979f6e6019d15f91ba56182f1aaf68d61bf37fc6.1668595505.git.bblock@linux.ibm.comReviewed-by: Steffen Maier <maier@linux.ibm.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>