Re: [REGRESSION] 28676d869bbb (scsi: sg: check for valid direction before starting the request) breaks mtx tape library control

Jason L Tibbitts III
2017-07-26T20:19:31Z

>>>>> "JT" == Johannes Thumshirn <jthumshirn@suse.de> writes:

JT> It's probably best to just check for dxfer_len <= 2^28 to be valid
JT> as Doug suggested:

I can verify that patch on top of git head (as of a few hours ago) does
function properly.

It didn't apply directly on top of 4.12 but even I can handle fixing
that up. The result (just deleting the function and changing the call
to a check for hp->dxfer_len >= SZ_256M) works fine and is at the end.

So thanks. If this goes in, please CC to stable.

- J<

diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c
index 82c33a6..aa6f1de 100644
--- a/drivers/scsi/sg.c
+++ b/drivers/scsi/sg.c
@@ -751,29 +751,6 @@ sg_new_write(Sg_fd *sfp, struct file *file, const char __user *buf,
return count;
}

-static bool sg_is_valid_dxfer(sg_io_hdr_t *hp)
-{
- switch (hp->dxfer_direction) {
- case SG_DXFER_NONE:
- if (hp->dxferp || hp->dxfer_len > 0)
- return false;
- return true;
- case SG_DXFER_TO_DEV:
- case SG_DXFER_FROM_DEV:
- case SG_DXFER_TO_FROM_DEV:
- if (!hp->dxferp || hp->dxfer_len == 0)
- return false;
- return true;
- case SG_DXFER_UNKNOWN:
- if ((!hp->dxferp && hp->dxfer_len) ||
- (hp->dxferp && hp->dxfer_len == 0))
- return false;
- return true;
- default:
- return false;
- }
-}
-
static int
sg_common_write(Sg_fd * sfp, Sg_request * srp,
unsigned char *cmnd, int timeout, int blocking)
@@ -794,7 +771,7 @@ sg_common_write(Sg_fd * sfp, Sg_request * srp,
"sg_common_write: scsi opcode=0x%02x, cmd_size=%d\n",
(int) cmnd[0], (int) hp->cmd_len));

- if (!sg_is_valid_dxfer(hp))
+ if (hp->dxfer_len >= SZ_256M)
return -EINVAL;

k = sg_start_req(srp, cmnd);