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bsg-lib: fix kernel panic resulting from missing allocation of reply-…
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…buffer

Since we split the scsi_request out of struct request bsg fails to
provide a reply-buffer for the drivers. This was done via the pointer
for sense-data, that is not preallocated anymore.

Failing to allocate/assign it results in illegal dereferences because
LLDs use this pointer unquestioned.

An example panic on s390x, using the zFCP driver, looks like this (I had
debugging on, otherwise NULL-pointer dereferences wouldn't even panic on
s390x):

Unable to handle kernel pointer dereference in virtual kernel address space
Failing address: 6b6b6b6b6b6b6000 TEID: 6b6b6b6b6b6b6403
Fault in home space mode while using kernel ASCE.
AS:0000000001590007 R3:0000000000000024
Oops: 0038 ilc:2 [#1] PREEMPT SMP DEBUG_PAGEALLOC
Modules linked in: <Long List>
CPU: 2 PID: 0 Comm: swapper/2 Not tainted 4.12.0-bsg-regression+ #3
Hardware name: IBM 2964 N96 702 (z/VM 6.4.0)
task: 0000000065cb0100 task.stack: 0000000065cb4000
Krnl PSW : 0704e00180000000 000003ff801e4156 (zfcp_fc_ct_els_job_handler+0x16/0x58 [zfcp])
           R:0 T:1 IO:1 EX:1 Key:0 M:1 W:0 P:0 AS:3 CC:2 PM:0 RI:0 EA:3
Krnl GPRS: 0000000000000001 000000005fa9d0d0 000000005fa9d078 0000000000e16866
           000003ff00000290 6b6b6b6b6b6b6b6b 0000000059f78f00 000000000000000f
           00000000593a0958 00000000593a0958 0000000060d88800 000000005ddd4c38
           0000000058b50100 07000000659cba08 000003ff801e8556 00000000659cb9a8
Krnl Code: 000003ff801e4146: e31020500004        lg      %r1,80(%r2)
           000003ff801e414c: 58402040           l       %r4,64(%r2)
          #000003ff801e4150: e35020200004       lg      %r5,32(%r2)
          >000003ff801e4156: 50405004           st      %r4,4(%r5)
           000003ff801e415a: e54c50080000       mvhi    8(%r5),0
           000003ff801e4160: e33010280012       lt      %r3,40(%r1)
           000003ff801e4166: a718fffb           lhi     %r1,-5
           000003ff801e416a: 1803               lr      %r0,%r3
Call Trace:
([<000003ff801e8556>] zfcp_fsf_req_complete+0x726/0x768 [zfcp])
 [<000003ff801ea82a>] zfcp_fsf_reqid_check+0x102/0x180 [zfcp]
 [<000003ff801eb980>] zfcp_qdio_int_resp+0x230/0x278 [zfcp]
 [<00000000009b91b6>] qdio_kick_handler+0x2ae/0x2c8
 [<00000000009b9e3e>] __tiqdio_inbound_processing+0x406/0xc10
 [<00000000001684c2>] tasklet_action+0x15a/0x1d8
 [<0000000000bd28ec>] __do_softirq+0x3ec/0x848
 [<00000000001675a4>] irq_exit+0x74/0xf8
 [<000000000010dd6a>] do_IRQ+0xba/0xf0
 [<0000000000bd19e8>] io_int_handler+0x104/0x2d4
 [<00000000001033b6>] enabled_wait+0xb6/0x188
([<000000000010339e>] enabled_wait+0x9e/0x188)
 [<000000000010396a>] arch_cpu_idle+0x32/0x50
 [<0000000000bd0112>] default_idle_call+0x52/0x68
 [<00000000001cd0fa>] do_idle+0x102/0x188
 [<00000000001cd41e>] cpu_startup_entry+0x3e/0x48
 [<0000000000118c64>] smp_start_secondary+0x11c/0x130
 [<0000000000bd2016>] restart_int_handler+0x62/0x78
 [<0000000000000000>]           (null)
INFO: lockdep is turned off.
Last Breaking-Event-Address:
 [<000003ff801e41d6>] zfcp_fc_ct_job_handler+0x3e/0x48 [zfcp]

Kernel panic - not syncing: Fatal exception in interrupt

This patch moves bsg-lib to allocate and setup struct bsg_job ahead of
time, including the allocation of a buffer for the reply-data.

This means, struct bsg_job is not allocated separately anymore, but as part
of struct request allocation - similar to struct scsi_cmd. Reflect this in
the function names that used to handle creation/destruction of struct
bsg_job.

Reported-by: Steffen Maier <maier@linux.vnet.ibm.com>
Suggested-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Benjamin Block <bblock@linux.vnet.ibm.com>
Fixes: 82ed4db ("block: split scsi_request out of struct request")
Cc: <stable@vger.kernel.org> #4.11+
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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@Benjamin-Block @axboe
Benjamin-Block authored and axboe committed Aug 24, 2017
1 parent 1e6ec9e commit 50b4d48
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Showing 3 changed files with 46 additions and 31 deletions.
74 changes: 44 additions & 30 deletions block/bsg-lib.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -29,26 +29,25 @@
#include <scsi/scsi_cmnd.h>

/**
* bsg_destroy_job - routine to teardown/delete a bsg job
* bsg_teardown_job - routine to teardown a bsg job
* @job: bsg_job that is to be torn down
*/
static void bsg_destroy_job(struct kref *kref)
static void bsg_teardown_job(struct kref *kref)
{
struct bsg_job *job = container_of(kref, struct bsg_job, kref);
struct request *rq = job->req;

blk_end_request_all(rq, BLK_STS_OK);

put_device(job->dev); /* release reference for the request */

kfree(job->request_payload.sg_list);
kfree(job->reply_payload.sg_list);
kfree(job);

blk_end_request_all(rq, BLK_STS_OK);
}

void bsg_job_put(struct bsg_job *job)
{
kref_put(&job->kref, bsg_destroy_job);
kref_put(&job->kref, bsg_teardown_job);
}
EXPORT_SYMBOL_GPL(bsg_job_put);

Expand Down Expand Up @@ -100,7 +99,7 @@ EXPORT_SYMBOL_GPL(bsg_job_done);
*/
static void bsg_softirq_done(struct request *rq)
{
struct bsg_job *job = rq->special;
struct bsg_job *job = blk_mq_rq_to_pdu(rq);

bsg_job_put(job);
}
Expand All @@ -122,33 +121,20 @@ static int bsg_map_buffer(struct bsg_buffer *buf, struct request *req)
}

/**
* bsg_create_job - create the bsg_job structure for the bsg request
* bsg_prepare_job - create the bsg_job structure for the bsg request
* @dev: device that is being sent the bsg request
* @req: BSG request that needs a job structure
*/
static int bsg_create_job(struct device *dev, struct request *req)
static int bsg_prepare_job(struct device *dev, struct request *req)
{
struct request *rsp = req->next_rq;
struct request_queue *q = req->q;
struct scsi_request *rq = scsi_req(req);
struct bsg_job *job;
struct bsg_job *job = blk_mq_rq_to_pdu(req);
int ret;

BUG_ON(req->special);

job = kzalloc(sizeof(struct bsg_job) + q->bsg_job_size, GFP_KERNEL);
if (!job)
return -ENOMEM;

req->special = job;
job->req = req;
if (q->bsg_job_size)
job->dd_data = (void *)&job[1];
job->request = rq->cmd;
job->request_len = rq->cmd_len;
job->reply = rq->sense;
job->reply_len = SCSI_SENSE_BUFFERSIZE; /* Size of sense buffer
* allocated */

if (req->bio) {
ret = bsg_map_buffer(&job->request_payload, req);
if (ret)
Expand Down Expand Up @@ -187,7 +173,6 @@ static void bsg_request_fn(struct request_queue *q)
{
struct device *dev = q->queuedata;
struct request *req;
struct bsg_job *job;
int ret;

if (!get_device(dev))
Expand All @@ -199,16 +184,15 @@ static void bsg_request_fn(struct request_queue *q)
break;
spin_unlock_irq(q->queue_lock);

ret = bsg_create_job(dev, req);
ret = bsg_prepare_job(dev, req);
if (ret) {
scsi_req(req)->result = ret;
blk_end_request_all(req, BLK_STS_OK);
spin_lock_irq(q->queue_lock);
continue;
}

job = req->special;
ret = q->bsg_job_fn(job);
ret = q->bsg_job_fn(blk_mq_rq_to_pdu(req));
spin_lock_irq(q->queue_lock);
if (ret)
break;
Expand All @@ -219,6 +203,35 @@ static void bsg_request_fn(struct request_queue *q)
spin_lock_irq(q->queue_lock);
}

static int bsg_init_rq(struct request_queue *q, struct request *req, gfp_t gfp)
{
struct bsg_job *job = blk_mq_rq_to_pdu(req);
struct scsi_request *sreq = &job->sreq;

memset(job, 0, sizeof(*job));

scsi_req_init(sreq);
sreq->sense_len = SCSI_SENSE_BUFFERSIZE;
sreq->sense = kzalloc(sreq->sense_len, gfp);
if (!sreq->sense)
return -ENOMEM;

job->req = req;
job->reply = sreq->sense;
job->reply_len = sreq->sense_len;
job->dd_data = job + 1;

return 0;
}

static void bsg_exit_rq(struct request_queue *q, struct request *req)
{
struct bsg_job *job = blk_mq_rq_to_pdu(req);
struct scsi_request *sreq = &job->sreq;

kfree(sreq->sense);
}

/**
* bsg_setup_queue - Create and add the bsg hooks so we can receive requests
* @dev: device to attach bsg device to
Expand All @@ -235,15 +248,16 @@ struct request_queue *bsg_setup_queue(struct device *dev, char *name,
q = blk_alloc_queue(GFP_KERNEL);
if (!q)
return ERR_PTR(-ENOMEM);
q->cmd_size = sizeof(struct scsi_request);
q->cmd_size = sizeof(struct bsg_job) + dd_job_size;
q->init_rq_fn = bsg_init_rq;
q->exit_rq_fn = bsg_exit_rq;
q->request_fn = bsg_request_fn;

ret = blk_init_allocated_queue(q);
if (ret)
goto out_cleanup_queue;

q->queuedata = dev;
q->bsg_job_size = dd_job_size;
q->bsg_job_fn = job_fn;
queue_flag_set_unlocked(QUEUE_FLAG_BIDI, q);
queue_flag_set_unlocked(QUEUE_FLAG_SCSI_PASSTHROUGH, q);
Expand Down
1 change: 0 additions & 1 deletion include/linux/blkdev.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -568,7 +568,6 @@ struct request_queue {

#if defined(CONFIG_BLK_DEV_BSG)
bsg_job_fn *bsg_job_fn;
int bsg_job_size;
struct bsg_class_device bsg_dev;
#endif

Expand Down
2 changes: 2 additions & 0 deletions include/linux/bsg-lib.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -24,6 +24,7 @@
#define _BLK_BSG_

#include <linux/blkdev.h>
#include <scsi/scsi_request.h>

struct request;
struct device;
Expand All @@ -37,6 +38,7 @@ struct bsg_buffer {
};

struct bsg_job {
struct scsi_request sreq;
struct device *dev;
struct request *req;

Expand Down

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