In contrast to the normal SCSI-lib, the BSG block-queue doesn't make use of
any extra init_rq_fn() to make additional allocations during
request-creation, and the request sense-pointer is not used to transport
SCSI sense data, but is used as backing for the bsg_job->reply pointer;
that in turn is used in the LLDs to store protocol IUs or similar stuff.
This 're-purposing' of the sense-pointer is done in the BSG blk-lib
(bsg_create_job()), during the queue-processing.
Failing to allocate/assign it results in illegal dereferences because LLDs
use this pointer unquestioned, as can be seen in the various
BSG-implementations:
drivers/scsi/libfc/fc_lport.c: fc_lport_bsg_request()
drivers/scsi/qla2xxx/qla_bsg.c: qla24xx_bsg_request()
drivers/scsi/qla4xxx/ql4_bsg.c: qla4xxx_process_vendor_specific()
drivers/s390/scsi/zfcp_fc.c: zfcp_fc_ct_els_job_handler()
...
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
To prevent this, allocate a buffer when the BSG blk-request is setup, and
before it is queued for LLD processing.
Reported-by: Steffen Maier <ma...@linux.vnet.ibm.com>
Signed-off-by: Benjamin Block <bbl...@linux.vnet.ibm.com>
Fixes: 82ed4db499b8 ("block: split scsi_request out of struct request")
Cc: <sta...@vger.kernel.org> #4.11+
---
block/bsg.c | 22 +++++++++++++++++-----
1 file changed, 17 insertions(+), 5 deletions(-)
diff --git a/block/bsg.c b/block/bsg.c
index 37663b664666..285b1b8126c3 100644
--- a/block/bsg.c
+++ b/block/bsg.c
@@ -74,6 +74,8 @@ static int bsg_major;
static struct kmem_cache *bsg_cmd_cachep;
+#define BSG_COMMAND_REPLY_BUFFERSIZE SCSI_SENSE_BUFFERSIZE
+
/*
* our internal command type
*/
@@ -85,6 +87,7 @@ struct bsg_command {
struct bio *bidi_bio;
int err;
struct sg_io_v4 hdr;
+ u8 reply_buffer[BSG_COMMAND_REPLY_BUFFERSIZE];
};
static void bsg_free_command(struct bsg_command *bc)
@@ -137,7 +140,7 @@ static inline struct hlist_head *bsg_dev_idx_hash(int index)
static int blk_fill_sgv4_hdr_rq(struct request_queue *q, struct request *rq,
struct sg_io_v4 *hdr, struct bsg_device *bd,
- fmode_t has_write_perm)
+ u8 *reply_buffer, fmode_t has_write_perm)
{
struct scsi_request *req = scsi_req(rq);
@@ -162,6 +165,10 @@ static int blk_fill_sgv4_hdr_rq(struct request_queue *q,
struct request *rq,
*/
req->cmd_len = hdr->request_len;
+ /* this is later asigned to bsg_job as reply */
+ req->sense = reply_buffer;
+ req->sense_len = BSG_COMMAND_REPLY_BUFFERSIZE;
+
rq->timeout = msecs_to_jiffies(hdr->timeout);
if (!rq->timeout)
rq->timeout = q->sg_timeout;
@@ -206,7 +213,8 @@ bsg_validate_sgv4_hdr(struct sg_io_v4 *hdr, int *op)
* map sg_io_v4 to a request.
*/
static struct request *
-bsg_map_hdr(struct bsg_device *bd, struct sg_io_v4 *hdr, fmode_t
has_write_perm)
+bsg_map_hdr(struct bsg_device *bd, struct sg_io_v4 *hdr, fmode_t
has_write_perm,
+ u8 *reply_buffer)
{
struct request_queue *q = bd->queue;
struct request *rq, *next_rq = NULL;
@@ -237,7 +245,8 @@ bsg_map_hdr(struct bsg_device *bd, struct sg_io_v4 *hdr,
fmode_t has_write_perm)
if (IS_ERR(rq))
return rq;
- ret = blk_fill_sgv4_hdr_rq(q, rq, hdr, bd, has_write_perm);
+ ret = blk_fill_sgv4_hdr_rq(q, rq, hdr, bd, reply_buffer,
+ has_write_perm);
if (ret)
goto out;
@@ -619,7 +628,8 @@ static int __bsg_write(struct bsg_device *bd, const char
__user *buf,
/*
* get a request, fill in the blanks, and add to request queue
*/
- rq = bsg_map_hdr(bd, &bc->hdr, has_write_perm);
+ rq = bsg_map_hdr(bd, &bc->hdr, has_write_perm,
+ bc->reply_buffer);
if (IS_ERR(rq)) {
ret = PTR_ERR(rq);
rq = NULL;
@@ -908,6 +918,7 @@ static long bsg_ioctl(struct file *file, unsigned int cmd,
unsigned long arg)
}
case SG_IO: {
struct request *rq;
+ u8 reply_buffer[BSG_COMMAND_REPLY_BUFFERSIZE] = { 0, };
struct bio *bio, *bidi_bio = NULL;
struct sg_io_v4 hdr;
int at_head;
@@ -915,7 +926,8 @@ static long bsg_ioctl(struct file *file, unsigned int cmd,
unsigned long arg)
if (copy_from_user(&hdr, uarg, sizeof(hdr)))
return -EFAULT;
- rq = bsg_map_hdr(bd, &hdr, file->f_mode & FMODE_WRITE);
+ rq = bsg_map_hdr(bd, &hdr, file->f_mode & FMODE_WRITE,
+ reply_buffer);
if (IS_ERR(rq))
return PTR_ERR(rq);
--
2.12.2
