On 2021-11-01 11:06 p.m., Bart Van Assche wrote:
On 11/1/21 18:56, Douglas Gilbert wrote:
On 2021-11-01 4:20 p.m., Bart Van Assche wrote:
One of the functions in the call stack in the first message of this email
thread is sg_io(). I am not aware of any documentation that specifies whether
it is valid to set cmd_len in the sg_io header to zero. My opinion is that
the SG_IO implementation should either reject cmd_len == 0 or set cmd_len
to a valid value if it is zero.
For the sg driver in production, the v3 interface users (including
ioctl(<sg_fd>, SG_IO,) ) have this check:
if ((!hp->cmdp) || (hp->cmd_len < 6) || (hp->cmd_len > sizeof (cmnd))) {
sg_remove_request(sfp, srp);
return -EMSGSIZE;
}
Hi Doug,
Thanks for having taken a look. I found the above check in sg_new_write(). To me
that function seems to come from a code path that is unrelated to sg_io(), the
function shown in the call stack in the email at the start of this thread. Maybe
I overlooked something but I haven't found a minimum size check for hdr->cmd_len
in sg_io() before the blk_execute_rq() call. Should such a check perhaps be added?
I guess it came from ioctl(<non_sg_fd>, SG_IO, ) and I found no lower bound
check when I looked in lk 5.15.0 . No-one has complained to me about the
hp->cmd_len < 6
check in the sg driver ***. So I think such a check may be useful in the
scsi_fill_sghdr_rq() function in drivers/scsi/scsi_ioctl.c . And a return
of -EMSGSIZE seems to be tailor made for this situation.
Doug Gilbert
*** It is possible a vendor specific command could be between 1 and 5 bytes
long, but that would probably be an unwise choice.
