On 07/20/2014 01:23 PM, Christoph Hellwig wrote:
> Signed-off-by: Christoph Hellwig <h...@lst.de>
Hi Christoph I've quickly reviewed your code and have a few questions
> ---
> block/scsi_ioctl.c | 24 +++++++++++++++++-------
> 1 file changed, 17 insertions(+), 7 deletions(-)
>
> diff --git a/block/scsi_ioctl.c b/block/scsi_ioctl.c
> index c4e6633..a804f3e 100644
> --- a/block/scsi_ioctl.c
> +++ b/block/scsi_ioctl.c
> @@ -288,8 +288,6 @@ static int sg_io(struct request_queue *q, struct gendisk
> *bd_disk,
>
> if (hdr->interface_id != 'S')
> return -EINVAL;
> - if (hdr->cmd_len > BLK_MAX_CDB)
> - return -EINVAL;
>
> if (hdr->dxfer_len > (queue_max_hw_sectors(q) << 9))
> return -EIO;
> @@ -306,14 +304,21 @@ static int sg_io(struct request_queue *q, struct
> gendisk *bd_disk,
> break;
> }
>
> + ret = -ENOMEM;
> rq = blk_get_request(q, writing ? WRITE : READ, GFP_KERNEL);
> if (!rq)
> - return -ENOMEM;
> + goto out;
> blk_rq_set_block_pc(rq);
>
> + if (hdr->cmd_len > BLK_MAX_CDB) {
> + rq->cmd = kzalloc(hdr->cmd_len, GFP_KERNEL);
So two things here:
- hdr->cmd_len is char so can be MAX of 255. I understand that 4 bytes
alignment is a SCSI
thing so you found no point of checking any max size?
- Why the zero alloc, if you are going to paste over it the exact same length.
Now if like in scsi
you need 4 bytes alignment and zero padding yes, but here you do not do this
(and probably shouldn't).
Hence why zero-alloc?
- Looking at sg.h where hdr->cmd_len is defined it stills has a comment of <=
16 you might want to
remove the comment by now.
> + if (!rq->cmd)
> + goto out_put_request;
> + }
> +
> ret = -EFAULT;
> if (blk_fill_sghdr_rq(q, rq, hdr, mode))
Inside here: blk_fill_sghdr_rq() calls blk_verify_command() which does:
(Below cmd[] is the buffer copied from user)
/* Anybody who can open the device can do a read-safe command */
if (test_bit(cmd[0], filter->read_ok))
return 0;
/* Write-safe commands require a writable open */
if (test_bit(cmd[0], filter->write_ok) && has_write_perm)
return 0;
Now I am not sure what type "Commands" you guys intend for these large commands
but if they are say SCSI-VARLEN this test will not work. Also a user might fool
the system with pretending to be "read" a device modifying command.
I would pass len to this test function and only permit these above if command is
<= 16. Any "special" large command is root only.
Thanks
Boaz
> - goto out;
> + goto out_free_cdb;
>
> if (hdr->iovec_count) {
> size_t iov_data_len;
> @@ -323,7 +328,7 @@ static int sg_io(struct request_queue *q, struct gendisk
> *bd_disk,
> 0, NULL, &iov);
> if (ret < 0) {
> kfree(iov);
> - goto out;
> + goto out_free_cdb;
> }
>
> iov_data_len = ret;
> @@ -346,7 +351,7 @@ static int sg_io(struct request_queue *q, struct gendisk
> *bd_disk,
> GFP_KERNEL);
>
> if (ret)
> - goto out;
> + goto out_free_cdb;
>
> bio = rq->bio;
> memset(sense, 0, sizeof(sense));
> @@ -365,8 +370,13 @@ static int sg_io(struct request_queue *q, struct gendisk
> *bd_disk,
> hdr->duration = jiffies_to_msecs(jiffies - start_time);
>
> ret = blk_complete_sghdr_rq(rq, hdr, bio);
> -out:
> +
> +out_free_cdb:
> + if (rq->cmd != rq->__cmd)
> + kfree(rq->cmd);
> +out_put_request:
> blk_put_request(rq);
> +out:
> return ret;
> }
>
>
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