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authorBenjamin Block <bblock@linux.ibm.com>2019-07-02 23:02:02 +0200
committerMartin K. Petersen <martin.petersen@oracle.com>2019-07-11 21:04:23 -0400
commit484647088826f2f651acbda6bcf9536b8a466703 (patch)
tree1d69257e4c1e135187f6266fccf3e00a030a51fd /drivers/s390/scsi
parentscsi: zfcp: fix request object use-after-free in send path causing wrong traces (diff)
downloadlinux-dev-484647088826f2f651acbda6bcf9536b8a466703.tar.xz
linux-dev-484647088826f2f651acbda6bcf9536b8a466703.zip
scsi: zfcp: fix GCC compiler warning emitted with -Wmaybe-uninitialized
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>
Diffstat (limited to 'drivers/s390/scsi')
-rw-r--r--drivers/s390/scsi/zfcp_erp.c7
1 files changed, 7 insertions, 0 deletions
diff --git a/drivers/s390/scsi/zfcp_erp.c b/drivers/s390/scsi/zfcp_erp.c
index e8fc28dba8df..96f0d34e9459 100644
--- a/drivers/s390/scsi/zfcp_erp.c
+++ b/drivers/s390/scsi/zfcp_erp.c
@@ -11,6 +11,7 @@
#define pr_fmt(fmt) KMSG_COMPONENT ": " fmt
#include <linux/kthread.h>
+#include <linux/bug.h>
#include "zfcp_ext.h"
#include "zfcp_reqlist.h"
@@ -217,6 +218,12 @@ static struct zfcp_erp_action *zfcp_erp_setup_act(enum zfcp_erp_act_type need,
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);