linux-kernel - [PATCH] dasd_fba: Display '00000000' for zero page when dumping sense

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Date:   Mon, 18 Nov 2019 12:12:26 +0100
From:   Hannes Reinecke <hare@...e.de>
To:     Jan Hoeppner <hoeppner@...ux.ibm.com>
Cc:     Stefan Haberland <sth@...ux.ibm.com>, linux-s390@...r.kernel.org,
        Linux Kernel Mailinglist <linux-kernel@...r.kernel.org>,
        Hannes Reinecke <hare@...e.de>,
        Hannes Reinecke <hare@...e.com>,
        Sebastian Parschauer <sparschauer@...e.de>
Subject: [PATCH] dasd_fba: Display '00000000' for zero page when dumping sense

When a discard I/O fails, dasd_fba_dump_sense() will crash as it
tries to print out the CCW, and failing to take into account that
for discard I/O we have only one data pointer, not one per sg.
As the data pointer will always point to the zero page this patch
replaces the data pointer output with '00000000' to avoid the crash.

Signed-off-by: Hannes Reinecke <hare@...e.com>
[sparschauer: replaced "ccw" with "act", "snprintf" with "sprintf"]
[sparschauer v2: added missing curly braces to for loops]
Signed-off-by: Sebastian Parschauer <sparschauer@...e.de>
---
 drivers/s390/block/dasd_fba.c | 21 ++++++++++++++++++---
 1 file changed, 18 insertions(+), 3 deletions(-)

diff --git a/drivers/s390/block/dasd_fba.c b/drivers/s390/block/dasd_fba.c
index cbb770824226..4b867bd6b164 100644
--- a/drivers/s390/block/dasd_fba.c
+++ b/drivers/s390/block/dasd_fba.c
@@ -717,10 +717,15 @@ dasd_fba_dump_sense(struct dasd_device *device, struct dasd_ccw_req * req,
 			       " CCW %p: %08X %08X DAT:",
 			       act, ((int *) act)[0], ((int *) act)[1]);
 		for (count = 0; count < 32 && count < act->count;
-		     count += sizeof(int))
+		     count += sizeof(int)) {
+			if (act->flags & CCW_FLAG_SLI) {
+				len += sprintf(page + len, " 00000000");
+				break;
+			}
 			len += sprintf(page + len, " %08X",
 				       ((int *) (addr_t) act->cda)
 				       [(count>>2)]);
+		}
 		len += sprintf(page + len, "\n");
 		act++;
 	}
@@ -739,10 +744,15 @@ dasd_fba_dump_sense(struct dasd_device *device, struct dasd_ccw_req * req,
 			       " CCW %p: %08X %08X DAT:",
 			       act, ((int *) act)[0], ((int *) act)[1]);
 		for (count = 0; count < 32 && count < act->count;
-		     count += sizeof(int))
+		     count += sizeof(int)) {
+			if (act->flags & CCW_FLAG_SLI) {
+				len += sprintf(page + len, " 00000000");
+				break;
+			}
 			len += sprintf(page + len, " %08X",
 				       ((int *) (addr_t) act->cda)
 				       [(count>>2)]);
+		}
 		len += sprintf(page + len, "\n");
 		act++;
 	}
@@ -757,10 +767,15 @@ dasd_fba_dump_sense(struct dasd_device *device, struct dasd_ccw_req * req,
 			       " CCW %p: %08X %08X DAT:",
 			       act, ((int *) act)[0], ((int *) act)[1]);
 		for (count = 0; count < 32 && count < act->count;
-		     count += sizeof(int))
+		     count += sizeof(int)) {
+			if (act->flags & CCW_FLAG_SLI) {
+				len += sprintf(page + len, " 00000000");
+				break;
+			}
 			len += sprintf(page + len, " %08X",
 				       ((int *) (addr_t) act->cda)
 				       [(count>>2)]);
+		}
 		len += sprintf(page + len, "\n");
 		act++;
 	}
-- 
2.16.4