From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: linux-kernel@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
stable@vger.kernel.org, Benjamin Block <bblock@linux.ibm.com>,
Jens Remus <jremus@linux.ibm.com>,
Steffen Maier <maier@linux.ibm.com>,
"Martin K. Petersen" <martin.petersen@oracle.com>,
Sasha Levin <sashal@kernel.org>
Subject: [PATCH 4.4 09/22] scsi: zfcp: fix GCC compiler warning emitted with -Wmaybe-uninitialized
Date: Mon, 5 Aug 2019 15:02:46 +0200 [thread overview]
Message-ID: <20190805124920.647834364@linuxfoundation.org> (raw)
In-Reply-To: <20190805124918.070468681@linuxfoundation.org>
[ Upstream commit 484647088826f2f651acbda6bcf9536b8a466703 ]
GCC v9 emits this warning:
CC drivers/s390/scsi/zfcp_erp.o
drivers/s390/scsi/zfcp_erp.c: In function 'zfcp_erp_action_enqueue':
drivers/s390/scsi/zfcp_erp.c:217:26: warning: 'erp_action' may be used uninitialized in this function [-Wmaybe-uninitialized]
217 | struct zfcp_erp_action *erp_action;
| ^~~~~~~~~~
This is a possible false positive case, as also documented in the GCC
documentations:
https://gcc.gnu.org/onlinedocs/gcc/Warning-Options.html#index-Wmaybe-uninitialized
The actual code-sequence is like this:
Various callers can invoke the function below with the argument "want"
being one of:
ZFCP_ERP_ACTION_REOPEN_ADAPTER,
ZFCP_ERP_ACTION_REOPEN_PORT_FORCED,
ZFCP_ERP_ACTION_REOPEN_PORT, or
ZFCP_ERP_ACTION_REOPEN_LUN.
zfcp_erp_action_enqueue(want, ...)
...
need = zfcp_erp_required_act(want, ...)
need = want
...
maybe: need = ZFCP_ERP_ACTION_REOPEN_PORT
maybe: need = ZFCP_ERP_ACTION_REOPEN_ADAPTER
...
return need
...
zfcp_erp_setup_act(need, ...)
struct zfcp_erp_action *erp_action; // <== line 217
...
switch(need) {
case ZFCP_ERP_ACTION_REOPEN_LUN:
...
erp_action = &zfcp_sdev->erp_action;
WARN_ON_ONCE(erp_action->port != port); // <== access
...
break;
case ZFCP_ERP_ACTION_REOPEN_PORT:
case ZFCP_ERP_ACTION_REOPEN_PORT_FORCED:
...
erp_action = &port->erp_action;
WARN_ON_ONCE(erp_action->port != port); // <== access
...
break;
case ZFCP_ERP_ACTION_REOPEN_ADAPTER:
...
erp_action = &adapter->erp_action;
WARN_ON_ONCE(erp_action->port != NULL); // <== access
...
break;
}
...
WARN_ON_ONCE(erp_action->adapter != adapter); // <== access
When zfcp_erp_setup_act() is called, 'need' will never be anything else
than one of the 4 possible enumeration-names that are used in the
switch-case, and 'erp_action' is initialized for every one of them, before
it is used. Thus the warning is a false positive, as documented.
We introduce the extra if{} in the beginning to create an extra code-flow,
so the compiler can be convinced that the switch-case will never see any
other value.
BUG_ON()/BUG() is intentionally not used to not crash anything, should
this ever happen anyway - right now it's impossible, as argued above; and
it doesn't introduce a 'default:' switch-case to retain warnings should
'enum zfcp_erp_act_type' ever be extended and no explicit case be
introduced. See also v5.0 commit 399b6c8bc9f7 ("scsi: zfcp: drop old
default switch case which might paper over missing case").
Signed-off-by: Benjamin Block <bblock@linux.ibm.com>
Reviewed-by: Jens Remus <jremus@linux.ibm.com>
Reviewed-by: Steffen Maier <maier@linux.ibm.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/s390/scsi/zfcp_erp.c | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/drivers/s390/scsi/zfcp_erp.c b/drivers/s390/scsi/zfcp_erp.c
index abe460eac7126..cc62d8cc8cfdd 100644
--- a/drivers/s390/scsi/zfcp_erp.c
+++ b/drivers/s390/scsi/zfcp_erp.c
@@ -10,6 +10,7 @@
#define pr_fmt(fmt) KMSG_COMPONENT ": " fmt
#include <linux/kthread.h>
+#include <linux/bug.h>
#include "zfcp_ext.h"
#include "zfcp_reqlist.h"
@@ -244,6 +245,12 @@ static struct zfcp_erp_action *zfcp_erp_setup_act(int need, u32 act_status,
struct zfcp_erp_action *erp_action;
struct zfcp_scsi_dev *zfcp_sdev;
+ if (WARN_ON_ONCE(need != ZFCP_ERP_ACTION_REOPEN_LUN &&
+ need != ZFCP_ERP_ACTION_REOPEN_PORT &&
+ need != ZFCP_ERP_ACTION_REOPEN_PORT_FORCED &&
+ need != ZFCP_ERP_ACTION_REOPEN_ADAPTER))
+ return NULL;
+
switch (need) {
case ZFCP_ERP_ACTION_REOPEN_LUN:
zfcp_sdev = sdev_to_zfcp(sdev);
--
2.20.1
next prev parent reply other threads:[~2019-08-05 13:04 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-05 13:02 [PATCH 4.4 00/22] 4.4.188-stable review Greg Kroah-Hartman
2019-08-05 13:02 ` [PATCH 4.4 01/22] ARM: riscpc: fix DMA Greg Kroah-Hartman
2019-08-05 13:02 ` [PATCH 4.4 02/22] ARM: dts: rockchip: Mark that the rk3288 timer might stop in suspend Greg Kroah-Hartman
2019-08-05 13:02 ` [PATCH 4.4 03/22] kernel/module.c: Only return -EEXIST for modules that have finished loading Greg Kroah-Hartman
2019-08-05 13:02 ` [PATCH 4.4 04/22] MIPS: lantiq: Fix bitfield masking Greg Kroah-Hartman
2019-08-05 13:02 ` [PATCH 4.4 05/22] dmaengine: rcar-dmac: Reject zero-length slave DMA requests Greg Kroah-Hartman
2019-08-05 13:02 ` [PATCH 4.4 06/22] fs/adfs: super: fix use-after-free bug Greg Kroah-Hartman
2019-08-05 13:02 ` [PATCH 4.4 07/22] btrfs: fix minimum number of chunk errors for DUP Greg Kroah-Hartman
2019-08-05 13:02 ` [PATCH 4.4 08/22] ceph: fix improper use of smp_mb__before_atomic() Greg Kroah-Hartman
2019-08-05 13:02 ` Greg Kroah-Hartman [this message]
2019-08-05 13:02 ` [PATCH 4.4 10/22] ACPI: fix false-positive -Wuninitialized warning Greg Kroah-Hartman
2019-08-05 13:02 ` [PATCH 4.4 11/22] be2net: Signal that the device cannot transmit during reconfiguration Greg Kroah-Hartman
2019-08-05 13:02 ` [PATCH 4.4 12/22] x86/apic: Silence -Wtype-limits compiler warnings Greg Kroah-Hartman
2019-08-05 13:02 ` [PATCH 4.4 13/22] x86: math-emu: Hide clang warnings for 16-bit overflow Greg Kroah-Hartman
2019-08-05 13:02 ` [PATCH 4.4 14/22] mm/cma.c: fail if fixed declaration cant be honored Greg Kroah-Hartman
2019-08-05 13:02 ` [PATCH 4.4 15/22] coda: add error handling for fget Greg Kroah-Hartman
2019-08-05 13:02 ` [PATCH 4.4 16/22] coda: fix build using bare-metal toolchain Greg Kroah-Hartman
2019-08-05 13:02 ` [PATCH 4.4 17/22] uapi linux/coda_psdev.h: move upc_req definition from uapi to kernel side headers Greg Kroah-Hartman
2019-08-05 13:02 ` [PATCH 4.4 18/22] ipc/mqueue.c: only perform resource calculation if user valid Greg Kroah-Hartman
2019-08-05 13:02 ` [PATCH 4.4 19/22] x86/kvm: Dont call kvm_spurious_fault() from .fixup Greg Kroah-Hartman
2019-08-05 13:02 ` [PATCH 4.4 20/22] selinux: fix memory leak in policydb_init() Greg Kroah-Hartman
2019-08-05 13:02 ` [PATCH 4.4 21/22] s390/dasd: fix endless loop after read unit address configuration Greg Kroah-Hartman
2019-08-05 13:02 ` [PATCH 4.4 22/22] xen/swiotlb: fix condition for calling xen_destroy_contiguous_region() Greg Kroah-Hartman
2019-08-05 17:35 ` [PATCH 4.4 00/22] 4.4.188-stable review kernelci.org bot
2019-08-06 1:14 ` shuah
2019-08-06 7:26 ` Naresh Kamboju
2019-08-06 15:48 ` Guenter Roeck
2019-08-06 18:28 ` Jon Hunter
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20190805124920.647834364@linuxfoundation.org \
--to=gregkh@linuxfoundation.org \
--cc=bblock@linux.ibm.com \
--cc=jremus@linux.ibm.com \
--cc=linux-kernel@vger.kernel.org \
--cc=maier@linux.ibm.com \
--cc=martin.petersen@oracle.com \
--cc=sashal@kernel.org \
--cc=stable@vger.kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).