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Subject[PATCH] Use ctlr directly in rdac_failover_get()
Date
rdac_failover_get references struct rdac_controller as
ctlr->ms_sdev->handler_data->ctlr for no apparent reason. Besides being
inefficient this also introduces a null-pointer dereference as
send_mode_select() sets ctlr->ms_sdev to NULL before calling
rdac_failover_get():

[ 18.432550] device-mapper: multipath service-time: version 0.3.0 loaded
[ 18.436124] BUG: unable to handle kernel NULL pointer dereference at 0000000000000790
[ 18.436129] IP: send_mode_select+0xca/0x560
[ 18.436129] PGD 0
[ 18.436130] P4D 0
[ 18.436130]
[ 18.436132] Oops: 0000 [#1] SMP
[ 18.436133] Modules linked in: dm_service_time sd_mod dm_multipath amdkfd amd_iommu_v2 radeon(+) i2c_algo_bit drm_kms_helper syscopyarea sysfillrect sysimgblt fb_sys_fops ttm qla2xxx drm serio_raw scsi_transport_fc bnx2 i2c_core dm_mirror dm_region_hash dm_log dm_mod
[ 18.436143] CPU: 4 PID: 443 Comm: kworker/u16:2 Not tainted 4.12.0-rc1.1.el7.test.x86_64 #1
[ 18.436144] Hardware name: IBM BladeCenter LS22 -[79013SG]-/Server Blade, BIOS -[L8E164AUS-1.07]- 05/25/2011
[ 18.436145] Workqueue: kmpath_rdacd send_mode_select
[ 18.436146] task: ffff880225116a40 task.stack: ffffc90002bd8000
[ 18.436148] RIP: 0010:send_mode_select+0xca/0x560
[ 18.436148] RSP: 0018:ffffc90002bdbda8 EFLAGS: 00010246
[ 18.436149] RAX: 0000000000000000 RBX: ffffc90002bdbe08 RCX: ffff88017ef04a80
[ 18.436150] RDX: ffffc90002bdbe08 RSI: ffff88017ef04a80 RDI: ffff8802248e4388
[ 18.436151] RBP: ffffc90002bdbe48 R08: 0000000000000000 R09: ffffffff81c104c0
[ 18.436151] R10: 00000000000001ff R11: 000000000000035a R12: ffffc90002bdbdd8
[ 18.436152] R13: ffff8802248e4390 R14: ffff880225152800 R15: ffff8802248e4400
[ 18.436153] FS: 0000000000000000(0000) GS:ffff880227d00000(0000) knlGS:0000000000000000
[ 18.436154] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 18.436154] CR2: 0000000000000790 CR3: 000000042535b000 CR4: 00000000000006e0
[ 18.436155] Call Trace:
[ 18.436159] ? rdac_activate+0x14e/0x150
[ 18.436161] ? refcount_dec_and_test+0x11/0x20
[ 18.436162] ? kobject_put+0x1c/0x50
[ 18.436165] ? scsi_dh_activate+0x6f/0xd0
[ 18.436168] process_one_work+0x149/0x360
[ 18.436170] worker_thread+0x4d/0x3c0
[ 18.436172] kthread+0x109/0x140
[ 18.436173] ? rescuer_thread+0x380/0x380
[ 18.436174] ? kthread_park+0x60/0x60
[ 18.436176] ret_from_fork+0x2c/0x40
[ 18.436177] Code: 49 c7 46 20 00 00 00 00 4c 89 ef c6 07 00 0f 1f 40 00 45 31 ed c7 45 b0 05 00 00 00 44 89 6d b4 4d 89 f5 4c 8b 75 a8 49 8b 45 20 <48> 8b b0 90 07 00 00 48 8b 56 10 8b 42 10 48 8d 7a 28 85 c0 0f
[ 18.436192] RIP: send_mode_select+0xca/0x560 RSP: ffffc90002bdbda8
[ 18.436192] CR2: 0000000000000790
[ 18.436198] ---[ end trace 40f3e4dca1ffabdd ]---
[ 18.436199] Kernel panic - not syncing: Fatal exception
[ 18.436222] Kernel Offset: disabled
[-- MARK -- Thu May 18 11:45:00 2017]

Signed-off-by: Artem Savkov <asavkov@redhat.com>
---
drivers/scsi/device_handler/scsi_dh_rdac.c | 10 ++++------
1 file changed, 4 insertions(+), 6 deletions(-)

diff --git a/drivers/scsi/device_handler/scsi_dh_rdac.c b/drivers/scsi/device_handler/scsi_dh_rdac.c
index 3cbab87..2ceff58 100644
--- a/drivers/scsi/device_handler/scsi_dh_rdac.c
+++ b/drivers/scsi/device_handler/scsi_dh_rdac.c
@@ -265,18 +265,16 @@ static unsigned int rdac_failover_get(struct rdac_controller *ctlr,
struct list_head *list,
unsigned char *cdb)
{
- struct scsi_device *sdev = ctlr->ms_sdev;
- struct rdac_dh_data *h = sdev->handler_data;
struct rdac_mode_common *common;
unsigned data_size;
struct rdac_queue_data *qdata;
u8 *lun_table;

- if (h->ctlr->use_ms10) {
+ if (ctlr->use_ms10) {
struct rdac_pg_expanded *rdac_pg;

data_size = sizeof(struct rdac_pg_expanded);
- rdac_pg = &h->ctlr->mode_select.expanded;
+ rdac_pg = &ctlr->mode_select.expanded;
memset(rdac_pg, 0, data_size);
common = &rdac_pg->common;
rdac_pg->page_code = RDAC_PAGE_CODE_REDUNDANT_CONTROLLER + 0x40;
@@ -288,7 +286,7 @@ static unsigned int rdac_failover_get(struct rdac_controller *ctlr,
struct rdac_pg_legacy *rdac_pg;

data_size = sizeof(struct rdac_pg_legacy);
- rdac_pg = &h->ctlr->mode_select.legacy;
+ rdac_pg = &ctlr->mode_select.legacy;
memset(rdac_pg, 0, data_size);
common = &rdac_pg->common;
rdac_pg->page_code = RDAC_PAGE_CODE_REDUNDANT_CONTROLLER;
@@ -304,7 +302,7 @@ static unsigned int rdac_failover_get(struct rdac_controller *ctlr,
}

/* Prepare the command. */
- if (h->ctlr->use_ms10) {
+ if (ctlr->use_ms10) {
cdb[0] = MODE_SELECT_10;
cdb[7] = data_size >> 8;
cdb[8] = data_size & 0xff;
--
1.8.3.1
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