On Sun, Dec 18, 2016 at 09:44:27PM +0100, Nicolas Iooss wrote:
> Hello,
>
> Currently on Linus master tree and in linux-next [1],
> bfad_im_bsg_els_ct_request() code starts with the following code:
>
> int
> bfad_im_bsg_els_ct_request(struct bsg_job *job)
> {
> /*...*/
> struct fc_bsg_request *bsg_request = bsg_request;
> struct fc_bsg_reply *bsg_reply = job->reply;
> uint32_t command_type = bsg_request->msgcode;
>
> The local variable "bsg_request" is initialized to itself (which would
> usually mean it is uninitialized) but it is dereferenced in order to get
> its "msgcode" field. As I am quite new to the kernel code and
> dereferencing self-initialized local variables looks black magic to me,
> could you please describe why this code is valid?
>
> It has recently been introduced by commit 01e0e15c8b3b ("scsi: don't use
> fc_bsg_job::request and fc_bsg_job::reply directly").
>
> Thanks,
> Nicolas Iooss
>
> [1]
> https://git.kernel.org/cgit/linux/kernel/git/next/linux-next.git/tree/drivers/scsi/bfa/bfad_bsg.c?id=06548160dfecd1983ffd9d6795242a5cda095da5#n3356
Yes this is wrong. bsg_request should point to job->request:
diff --git a/drivers/scsi/bfa/bfad_bsg.c b/drivers/scsi/bfa/bfad_bsg.c
index a9a0016..b2e8c0d 100644
--- a/drivers/scsi/bfa/bfad_bsg.c
+++ b/drivers/scsi/bfa/bfad_bsg.c
@@ -3363,7 +3363,7 @@ struct bfad_buf_info *
struct bfad_fcxp *drv_fcxp;
struct bfa_fcs_lport_s *fcs_port;
struct bfa_fcs_rport_s *fcs_rport;
- struct fc_bsg_request *bsg_request = bsg_request;
+ struct fc_bsg_request *bsg_request = job->request;
struct fc_bsg_reply *bsg_reply = job->reply;
uint32_t command_type = bsg_request->msgcode;
unsigned long flags;
I'll send out an official patch soon, thanks for the report.
Johannes
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