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Steffen Maier 0ad68e6212 scsi: zfcp: fix missing erp_lock in port recovery trigger for point-to-point 
commit 819732be9f upstream.

v2.6.27 commit cc8c282963 ("[SCSI] zfcp: Automatically attach remote
ports") introduced zfcp automatic port scan.

Before that, the user had to use the sysfs attribute "port_add" of an FCP
device (adapter) to add and open remote (target) ports, even for the remote
peer port in point-to-point topology. That code path did a proper port open
recovery trigger taking the erp_lock.

Since above commit, a new helper function zfcp_erp_open_ptp_port()
performed an UNlocked port open recovery trigger. This can race with other
parallel recovery triggers. In zfcp_erp_action_enqueue() this could corrupt
e.g. adapter->erp_total_count or adapter->erp_ready_head.

As already found for fabric topology in v4.17 commit fa89adba19 ("scsi:
zfcp: fix infinite iteration on ERP ready list"), there was an endless loop
during tracing of rport (un)block.  A subsequent v4.18 commit 9e156c54ac
("scsi: zfcp: assert that the ERP lock is held when tracing a recovery
trigger") introduced a lockdep assertion for that case.

As a side effect, that lockdep assertion now uncovered the unlocked code
path for PtP. It is from within an adapter ERP action:

zfcp_erp_strategy[1479]  intentionally DROPs erp lock around
                         zfcp_erp_strategy_do_action()
zfcp_erp_strategy_do_action[1441]      NO erp lock
zfcp_erp_adapter_strategy[876]         NO erp lock
zfcp_erp_adapter_strategy_open[855]    NO erp lock
zfcp_erp_adapter_strategy_open_fsf[806]NO erp lock
zfcp_erp_adapter_strat_fsf_xconf[772]  erp lock only around
                                       zfcp_erp_action_to_running(),
                                       BUT *_not_* around
                                       zfcp_erp_enqueue_ptp_port()
zfcp_erp_enqueue_ptp_port[728]         BUG: *_not_* taking erp lock
_zfcp_erp_port_reopen[432]             assumes to be called with erp lock
zfcp_erp_action_enqueue[314]           assumes to be called with erp lock
zfcp_dbf_rec_trig[288]                 _checks_ to be called with erp lock:
	lockdep_assert_held(&adapter->erp_lock);

It causes the following lockdep warning:

WARNING: CPU: 2 PID: 775 at drivers/s390/scsi/zfcp_dbf.c:288
                            zfcp_dbf_rec_trig+0x16a/0x188
no locks held by zfcperp0.0.17c0/775.

Fix this by using the proper locked recovery trigger helper function.

Link: https://lore.kernel.org/r/20200312174505.51294-2-maier@linux.ibm.com
Fixes: cc8c282963 ("[SCSI] zfcp: Automatically attach remote ports")
Cc: <stable@vger.kernel.org> #v2.6.27+
Reviewed-by: Jens Remus <jremus@linux.ibm.com>
Reviewed-by: Benjamin Block <bblock@linux.ibm.com>
Signed-off-by: Steffen Maier <maier@linux.ibm.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
 		2020-04-17 10:50:18 +02:00
Documentation ALSA: hda/realtek - Remove now-unnecessary XPS 13 headphone noise fixups 2020-04-17 10:50:08 +02:00
LICENSES LICENSES: Rename other to deprecated 2019-05-03 06:34:32 -06:00
arch arm64: dts: allwinner: h5: Fix PMU compatible 2020-04-17 10:50:17 +02:00
block block, bfq: fix use-after-free in bfq_idle_slice_timer_body 2020-04-17 10:50:05 +02:00
certs PKCS#7: Refactor verify_pkcs7_signature() 2019-08-05 18:40:18 -04:00
crypto crypto: rng - Fix a refcounting bug in crypto_rng_reset() 2020-04-17 10:50:16 +02:00
drivers scsi: zfcp: fix missing erp_lock in port recovery trigger for point-to-point 2020-04-17 10:50:18 +02:00
fs io_uring: honor original task RLIMIT_FSIZE 2020-04-17 10:50:16 +02:00
include xarray: Fix early termination of xas_for_each_marked 2020-04-17 10:50:18 +02:00
init kbuild: remove header compile test 2020-03-05 16:43:47 +01:00
ipc Revert "ipc,sem: remove uneeded sem_undo_list lock usage in exit_sem()" 2020-02-28 17:22:20 +01:00
kernel sched/core: Remove duplicate assignment in sched_tick_remote() 2020-04-17 10:50:17 +02:00
lib xarray: Fix early termination of xas_for_each_marked 2020-04-17 10:50:18 +02:00
mm mm, memcg: do not high throttle allocators based on wraparound 2020-04-17 10:50:17 +02:00
net cfg80211: Do not warn on same channel at the end of CSA 2020-04-17 10:49:59 +02:00
samples samples/bpf: Set -fno-stack-protector when building BPF programs 2020-02-24 08:36:36 +01:00
scripts kconfig: introduce m32-flag and m64-flag 2020-04-08 09:08:37 +02:00
security KEYS: reaching the keys quotas correctly 2020-04-17 10:50:11 +02:00
sound ALSA: hda/realtek - Add quirk for MSI GL63 2020-04-17 10:50:08 +02:00
tools xarray: Fix early termination of xas_for_each_marked 2020-04-17 10:50:18 +02:00
usr initramfs: restore default compression behavior 2020-04-08 09:08:38 +02:00
virt KVM: Check for a bad hva before dropping into the ghc slow path 2020-03-05 16:43:48 +01:00
.clang-format clang-format: Update with the latest for_each macro list 2019-08-31 10:00:51 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: set git diff driver for C source code files 2016-10-07 18:46:30 -07:00
.gitignore Modules updates for v5.4 2019-09-22 10:34:46 -07:00
.mailmap ARM: SoC fixes 2019-11-10 13:41:59 -08:00
COPYING COPYING: use the new text with points to the license files 2018-03-23 12:41:45 -06:00
CREDITS MAINTAINERS: Remove Simon as Renesas SoC Co-Maintainer 2019-10-10 08:12:51 -07:00
Kbuild kbuild: do not descend to ./Kbuild when cleaning 2019-08-21 21:03:58 +09:00
Kconfig docs: kbuild: convert docs to ReST and rename to *.rst 2019-06-14 14:21:21 -06:00
MAINTAINERS MAINTAINERS: Update drm/i915 bug filing URL 2020-02-28 17:22:19 +01:00
Makefile Linux 5.4.32 2020-04-13 10:48:18 +02:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.