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Subject[PATCH 4.15 017/146] scsi: core: Avoid that ATA error handling can trigger a kernel hang or oops
Date
4.15-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Bart Van Assche <bart.vanassche@wdc.com>

commit 3be8828fc507cdafe7040a3dcf361a2bcd8e305b upstream.

Avoid that the recently introduced call_rcu() call in the SCSI core
triggers a double call_rcu() call.

Reported-by: Natanael Copa <ncopa@alpinelinux.org>
Reported-by: Damien Le Moal <damien.lemoal@wdc.com>
References: https://bugzilla.kernel.org/show_bug.cgi?id=198861
Fixes: 3bd6f43f5cb3 ("scsi: core: Ensure that the SCSI error handler gets woken up")
Signed-off-by: Bart Van Assche <bart.vanassche@wdc.com>
Reviewed-by: Damien Le Moal <damien.lemoal@wdc.com>
Tested-by: Damien Le Moal <damien.lemoal@wdc.com>
Cc: Natanael Copa <ncopa@alpinelinux.org>
Cc: Damien Le Moal <damien.lemoal@wdc.com>
Cc: Alexandre Oliva <oliva@gnu.org>
Cc: Pavel Tikhomirov <ptikhomirov@virtuozzo.com>
Cc: Hannes Reinecke <hare@suse.com>
Cc: Johannes Thumshirn <jthumshirn@suse.de>
Cc: <stable@vger.kernel.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/scsi/hosts.c | 3 ---
drivers/scsi/scsi_error.c | 5 +++--
drivers/scsi/scsi_lib.c | 2 ++
include/scsi/scsi_cmnd.h | 3 +++
include/scsi/scsi_host.h | 2 --
5 files changed, 8 insertions(+), 7 deletions(-)

--- a/drivers/scsi/hosts.c
+++ b/drivers/scsi/hosts.c
@@ -328,8 +328,6 @@ static void scsi_host_dev_release(struct
if (shost->work_q)
destroy_workqueue(shost->work_q);

- destroy_rcu_head(&shost->rcu);
-
if (shost->shost_state == SHOST_CREATED) {
/*
* Free the shost_dev device name here if scsi_host_alloc()
@@ -404,7 +402,6 @@ struct Scsi_Host *scsi_host_alloc(struct
INIT_LIST_HEAD(&shost->starved_list);
init_waitqueue_head(&shost->host_wait);
mutex_init(&shost->scan_mutex);
- init_rcu_head(&shost->rcu);

index = ida_simple_get(&host_index_ida, 0, 0, GFP_KERNEL);
if (index < 0)
--- a/drivers/scsi/scsi_error.c
+++ b/drivers/scsi/scsi_error.c
@@ -222,7 +222,8 @@ static void scsi_eh_reset(struct scsi_cm

static void scsi_eh_inc_host_failed(struct rcu_head *head)
{
- struct Scsi_Host *shost = container_of(head, typeof(*shost), rcu);
+ struct scsi_cmnd *scmd = container_of(head, typeof(*scmd), rcu);
+ struct Scsi_Host *shost = scmd->device->host;
unsigned long flags;

spin_lock_irqsave(shost->host_lock, flags);
@@ -258,7 +259,7 @@ void scsi_eh_scmd_add(struct scsi_cmnd *
* Ensure that all tasks observe the host state change before the
* host_failed change.
*/
- call_rcu(&shost->rcu, scsi_eh_inc_host_failed);
+ call_rcu(&scmd->rcu, scsi_eh_inc_host_failed);
}

/**
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -670,6 +670,7 @@ static bool scsi_end_request(struct requ
if (!blk_rq_is_scsi(req)) {
WARN_ON_ONCE(!(cmd->flags & SCMD_INITIALIZED));
cmd->flags &= ~SCMD_INITIALIZED;
+ destroy_rcu_head(&cmd->rcu);
}

if (req->mq_ctx) {
@@ -1150,6 +1151,7 @@ void scsi_initialize_rq(struct request *
struct scsi_cmnd *cmd = blk_mq_rq_to_pdu(rq);

scsi_req_init(&cmd->req);
+ init_rcu_head(&cmd->rcu);
cmd->jiffies_at_alloc = jiffies;
cmd->retries = 0;
}
--- a/include/scsi/scsi_cmnd.h
+++ b/include/scsi/scsi_cmnd.h
@@ -69,6 +69,9 @@ struct scsi_cmnd {
struct list_head list; /* scsi_cmnd participates in queue lists */
struct list_head eh_entry; /* entry for the host eh_cmd_q */
struct delayed_work abort_work;
+
+ struct rcu_head rcu;
+
int eh_eflags; /* Used by error handlr */

/*
--- a/include/scsi/scsi_host.h
+++ b/include/scsi/scsi_host.h
@@ -571,8 +571,6 @@ struct Scsi_Host {
struct blk_mq_tag_set tag_set;
};

- struct rcu_head rcu;
-
atomic_t host_busy; /* commands actually active on low-level */
atomic_t host_blocked;


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